Ola Nilsen

• Mboyi, Clève D.; Rogowska, Melania; Desbois, Nicolas; Nilsen, Ola; Hansen, Per-Anders & Gros, Claude P. (2026). Diversely substituted porphyrins for molecular layer deposition and comparative studies of their physical properties. Journal of Physical Chemistry C. ISSN 1932-7447. doi: 10.1021/acs.jpcc.6c04698. Full text in Research Archive Show summary

  Vapor-phase layer-by-layer deposition methods are capable of creating thin films of organic, inorganic, or hybrid organic–inorganic nanostructures. This approach allows the combination of the material properties of inorganic matrices with the molecular properties of organic molecules, such as building structures with optoelectronically active dye molecules. One such attractive class of dyes are the porphyrins. However, being macrocycles, their volatility is generally low, which significantly limits their use in vapor-based processes. We have therefore designed and synthesized variously substituted porphyrin macrocycles with the aim of tuning their sublimation properties, as well as their chemical reactivity, to enable their use in vapor deposition processes. A selection of these compounds has been used in molecular layer deposition (MLD) processes, proving their applicability and verifying that the porphyrin macrocycles retain their functional properties within the film material.

• Litterst, Maximilian; Jannasch, Ramon; Balagopalan, Manjunath; Görbitz, Carl Henrik; Nilsen, Ola & Berland, Kristian [Show all 7 contributors for this article] (2026). Humidity-Tunable Organic Ferroelectric with Low Coercive Field. ACS Materials Letters. 8(7), p. 1982–1989. doi: 10.1021/acsmaterialslett.6c00243. Full text in Research Archive Show summary

  As compared to their inorganic counterparts, organic ferroelectrics offer vast design freedom, enabling the creation of materials with unprecedented properties. Here, we present temperature- and humidity-dependent ferroelectric switching measurements on thin polycrystalline films of an organic ionic cocrystal that was identified by database mining as potentially ferroelectric. The experiments reveal exceptionally low coercive fields, down to ∼0.2 V/μm, depending on conditions, while maintaining reasonable remnant polarizations around 15 μC/cm2. We observe a pronounced dependence of the ferroelectric properties on switching frequency, temperature and, strikingly, ambient humidity. Interestingly, the ferroelectric behavior appears to be coupled to the complex electrical conductivity. We interpret our findings in terms of a multi-step polarization reversal mechanism, involving a combination of proton transfer and molecular rotations, where the former is thought to also be responsible for the observed long-range charge transport. These properties may find applications in new classes of tunable or environment-responsive ‘smart’ materials.

• Litterst, Maximilian; Balagopalan, Manjunath; Jannasch, Ramon; Sødahl, Elin Dypvik; Seyedraoufi, Seyedmojtaba & Gørbitz, Carl Henrik [Show all 9 contributors for this article] (2026). Experimentally confirmed ferroelectricity in organic compounds identified by database mining. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 28, p. 4636–4647. doi: 10.1039/d5cp03009a. Full text in Research Archive Show summary

  Compared to inorganic ferroelectrics, the breadth of polarization switching mechanisms in organic ferroelectrics is very broad and far from fully characterized or understood. Here, we experimentally investigate the absence or presence of ferroelectric properties in a selection of organic materials that have been identified by a data mining approach using heuristic measures to identify stretchability, aiming to assess the practical potential of this approach. From a set of 66 candidate materials, 4 were selected for detailed analysis. These were investigated structurally using powder X-ray diffraction and electrically, using capacitance–voltage spectroscopy and polarization hysteresis measurements. Despite large differences in stability and background conductivity, all compounds exhibited ferroelectric behavior at room temperature, with relatively large polarization values. Specifically, the ferroelectric properties of one material show a strong dependency on the ambient humidity, whereas another showed a strong coupling between background conductivity and ferroelectric switching. These effects are not yet fully understood and lie beyond the scope of this study. Of the remaining two compounds, one was found to be unstable at room temperature whereas the other displayed multiple polymorphs, complicating reproducibility and limiting their practical potential. Overall, these results confirm the relevance of the data mining prediction scheme and suggest that a significant fraction of the identified but so far untested materials may also be ferroelectric.

• Navaratnam, Jesintha; Bærland, Thomas Pedersen; Nilsen, Ola; Rekstad, Bernt Louni; Faber, Rowan Thomas & Eide, Nils (2025). Adverse Event Following Change in Brachytherapy Plaque-Cleaning Chemicals: A Case Series. Ocular Oncology and Pathology. ISSN 2296-4681. 11(3), p. 210–215. doi: 10.1159/000548234. Full text in Research Archive Show summary

  Introduction: The brachytherapy plaques used for uveal melanoma treatment are reused following sterilization processes. Here, we report patients with adverse reaction following a new cleaning procedure for brachytherapy plaques. Case Presentations: The brachytherapy plaque sewn on the outer eyewall would be removed following the delivery of calculated radiation dose. They are reused following standard calibration testing and sterilization processes. From September 2021 to January 2022, 6 patients treated with ruthenium-106 plaque brachytherapy presented with severe unilateral pain, eyelid swelling, and conjunctival injection with hemorrhage 1–2 days following plaque insertion. The surgeons observed a frosted appearance of the plaques in contrast to the normal shiny look during removal. The unusual severe postoperative reactions and the frosted appearance of plaques led to further investigations. A change in sterilization procedures with the use of LifeClean™ instead of PeraSafe™ was noticed. Ruthenium-106 brachytherapy plaques contain a uniformly distributed radioactive source covered by a thin silver shield. A test was performed by using two plates of pure silver that underwent its respective cleaning procedure using either PeraSafe™ or LifeClean™. Conclusion: The test results demonstrated formation of silver chloride with LifeClean™, while no such formation was demonstrated with PeraSafe™. We did not observe any new cases of severe postoperative reaction or frosting of plaques after changing back to PeraSafe™. Chlorine salt deposits probably contributed to severe inflammatory reaction of ocular surface.

• Bråtalien, Lars Botolv; Nilsen, Ola; Saha, Dipankar; Mohn, Chris Erik; Chatzitakis, Athanasios & Valldor, Björn Martin (2025). Layered anion ordering in oxide chloride Ca2TlO3Cl. Dalton Transactions. ISSN 1477-9226. 54(31), p. 11887–11894. doi: 10.1039/d5dt01111f. Full text in Research Archive Show summary

  Single crystals and polycrystals of the novel compound Ca2TlO3Cl can be obtained by gas-phase and solid-state reactions, respectively. The title compound's crystal structure is hexagonal (a = 3.8806(2) Å, c = 18.6168(7) Å, P63/mmc) as measured by single crystal X-ray diffraction. A Rietveld refinement on powder X-ray diffraction data confirms this crystal structure. The atomic arrangement can be described as a cation ordered anti-structure of ScAl3C3, with a homoleptically, five-fold oxygen coordinated Tl3+ that consitutes corner-sharing trigonal bipyramids. Between these Tl–O sheets, a Cl-layer is found, making the whole structure quasi-2D. Thermal expansion coefficients in the range 15–290 K, as estimated from X-ray powder diffraction data, reveal that the relative length of the crystallographic c-axis (α33) is more temperature dependent than that of the a-axis (α11) lengths. The brown color of the polycrystalline title compound was investigated by spectroscopic reflectometry measurements. These data suggest an optical band gap of either 1.4 eV (indirect) or about 2.4–2.7 eV (direct), depending on interpretation model. However, density funciton theory calculations deliver a band structure that indicates that indirect band gaps are most likely, but with a size of about 2.7 eV. This discrepancy is discussed as a result of further local excitation phenomena, like charge-transfers and crystal defects. Photo-electrochemical investigations suggest that the title compound has an n-type character and is electrochemically activated by solar light.

• Mandal, Arkalekha; Mohn, Chris Erik; Görbitz, Carl Henrik; Rogowska, Melania & Nilsen, Ola (2025). Elucidating the role of charge transfer on semiconductor properties in a new donor–acceptor cocrystal 1,5-dihydroxynaphthalene : TCNQ. Molecular Systems Design & Engineering. 10(7), p. 519–533. doi: 10.1039/d5me00033e. Full text in Research Archive Show summary

  In this work, we have investigated the semiconducting properties of an unprecedented 1 : 1 π-stacked donor–acceptor cocrystal of 1,5-dihydroxynaphthalene (DHN) as the π-donor (D) with 7,7′,8,8′-tetracyanoquinodimethane (TCNQ) as the π-acceptor (A). Molecular semiconductors with electron dominant transport, narrow bandgap, solution processing ability, air-stability are highly sought-after for application in n-channel organic field effect transistors. The DHN : TCNQ cocrystal shows n-type semiconductor nature with a narrow bandgap of around 1 eV, and a low LUMO energy level (−3.8 eV) making it less prone to areal degradation. The electron dominant transport in this cocrystal is described by assuming that electron and hole hop via a super-exchange mechanism along the mixed ⋯D–A⋯ π-stack direction. The participation of bridging molecular orbitals other than donor HOMO make a significant contribution to the super-exchange electron transfer, thus resulting in electron hopping from acceptor to acceptor which is four times larger than the value of hole hopping from donor to donor. Detailed analysis of crystal packing and electronic properties demonstrate that the super-exchange charge carrier transport is facilitated by strong π⋯π stacking interaction between the donor and acceptor, and prominent charge transfer.

• Rykkje, Linn; Nilsen, Ola & Sønsteby, Henrik Hovde (2025). Growth Characteristics and Electronic Properties of Epitaxial NdNiO3 Thin Films by Atomic Layer Deposition. ACS Applied Electronic Materials. 7(6), p. 2466–2475. doi: 10.1021/acsaelm.4c02306. Full text in Research Archive Show summary

  The transition to next-generation electronics is inevitable and will require innovative architectures and materials functionalities. The multifunctional and often strongly coupled behaviors of transition metal oxides can offer alternative pathways to more energy-efficient devices, such as transistors. Here, we study thin films of NdNiO3 for its potential as a transistor channel switching material owing to the metal–insulator transition it exhibits at ∼200 K in bulk. The thin films exhibit high structural integrity and relevant functional properties when deposited by atomic layer deposition (ALD) under industrial processing conditions, thus providing a viable pathway for device integration. By varying the ratio of binary oxide subcycles, we can precisely obtain the stoichiometric NdNiO3 composition for which the thin films become epitaxial as deposited at 225 °C on SrTiO3(001). Prior to annealing, the specific resistivities at room temperature show a dependence on the out-of-plane lattice parameter, c, with a nonlinear increase from 10–4 to 10–1 Ωcm as c increases. After annealing at 650 °C in air, both the out-of-plane lattice parameters and resistivities converge toward a narrow range (c = 3.789–3.794 Å and 10–4 Ωcm, respectively). X-ray diffraction and reciprocal space mapping reveal that annealing also has the effect of increasing the strain in the thin films; however, they remain partially relaxed from the substrate. A metal–insulator transition takes place at 140 K under cooling and 175 K upon heating back to room temperature.

• Lee, Changrim; Killi, Veronica Anne-Line Kathrine; Nilsen, Ola & Dartt, Darlene Ann (2025). Titaminates, a Biocompatible Titanium–Organic Hybrid Film, Support the Growth and Function of Conjunctival Epithelial Cells. American Journal of Ophthalmology. ISSN 0002-9394. 273, p. 62–73. doi: 10.1016/j.ajo.2025.02.004. Full text in Research Archive Show summary

  PURPOSE To find an ideal biosurface to regenerate conjunctival epithelium. DESIGN Experimental study. METHODS Pieces of human cadaveric conjunctival epithelium removed of connective tissues were randomly placed on 8 different biosurfaces to grow primary conjunctival epithelial cells for 9 to 14 days until the fastest growing cultures covered 80% to 90% of the film surface. Main outcome measures were growth, proliferation capacity, startification, mucin 5AC (MUC5AC) secretion, and compositional balance in cell types. RESULTS All titanium-based films (titaminates) supported the growth, stratification, proliferation, and MUC5AC secretion function of human primary conjunctival epithelial cells (HCjECs), but none of the zinc-based films grew cells at all. Although HCjECs’ ability to proliferate, stratify, and secrete MUC5AC per unit cell area was similar across all titaminates, titanium dioxide (TiO2) and glycine titaminates (TiG) outperformed TiD and TiGD in terms of outgrowth, recapitulation of native conjunctival epithelium, and compositional balance in cell types. When goblet cells (a subtype of HCjECs) were predominantly grown on these films by using a different culture medium, the results were similar in all aspects. CONCLUSIONS Given the body-friendly nature and clinically proven safety and efficacy of titanium, titaminates TiO2 and TiG have potential as an alternative bioactive substrate for conjunctival epithelium regeneration.

• Andersen, Eline Haug; Sannes, Johnny Andreas; Frøen, Emil Herman; Nilsen, Ola & Valldor, Björn Martin (2025). Diamagnetic sulfide Ba3Sc2S6 – With infinite [ScS6/2] chains as structural element. Journal of Solid State Chemistry. ISSN 0022-4596. 342. doi: 10.1016/j.jssc.2024.125105. Full text in Research Archive Show summary

  The sulfide Ba3Sc2S6 was synthesized by the conventional high-temperature solid-state technique in an inert atmosphere, utilizing sealed silica ampules with low internal pressure of Ar gas. The crystal structure was determined by single crystal X-ray diffraction and can be described by a trigonal crystal lattice with rhombohedral symmetry, R 3‾ c (No. 167), with powder diffraction unit cell parameters a = 12.0402(1) Å and c = 13.3893(2) Å. The compound crystallizes with the K4CdCl6-type structure, which has been used to describe homologous sulfides. This crystal structure shares features with the 2H-perovskites but contains infinite 1D chains, Niggli notation [ScS6/2]∞1, consisting of alternating, distorted octahedra and trigonal prisms connected by face-sharing. Ba3Sc2S6 is diamagnetic, as determined from magnetic susceptibility measurements. UV–Vis spectroscopy data suggest a direct bandgap of about 2.88 eV. Further, DFT calculations reveal a band gap of about 1.8 eV and 2.9 eV using the PBE and the HSE06 functional, respectively, of which the latter agrees perfectly with UV–Vis observations.

• Sannes, Johnny Andreas; Chatzitakis, Athanasios; Andersen, Niels Højmark; Nilsen, Ola; Frøen, Emil Herman & Valldor, Björn Martin (2024). Characterization and Solid-State UV-Vis Investigations of Photoelectrocatalytically Active La5Cl7[TeO3]4, a Mixed Anion Compound with Alternating 2D Layers of Oxygen and Chlorine. Inorganic Chemistry. ISSN 0020-1669. 63(40), p. 18632–18641. doi: 10.1021/acs.inorgchem.4c02392. Full text in Research Archive Show summary

  An oxide chloride, La5Cl7[TeO3]4, was synthesized using the conventional high-temperature solid-state synthesis technique in an inert atmosphere. This compound possesses a novel crystal structure that can be described with the triclinic space group P1̅ (No. 2) and unit cell parameters: a = 7.2634(3) Å, b = 8.1241(3) Å, c = 9.1993(3) Å, α = 79.373(1)°, β = 83.599(1)°, and γ = 82.511(1)°. The preference of Te(IV) to coordinate to oxygen and direct its lone pair toward the lower charged chlorine results in 2D layers of both oxygen and chlorine, alternating along the crystallographic b-direction. Homoleptic coordination, solely to oxygen, and heteroleptic coordination to oxygen and chlorine are observed for lanthanum, forming layers connected through edge-sharing polyhedra. In the crystal structure, two distinct tellurium positions are observed, with three close Te–O distances, emphasizing an active lone pair. The compound has been investigated by solid-state UV–vis measurements, and a band gap of 3.44 eV has been determined by DFT calculations. Detailed photoelectrochemical measurements clearly indicate that the title compound is photoelectrocatalytically active, showing an n-type behavior. Raman spectroscopy confirms that complex tellurite ions are present in the crystal structure; several observed bands can be assigned to Te–O stretching, reflecting the relatively low crystallographic symmetry of the title compound.

• Dziadkowiec, Joanna; Linga, Gaute; Kalchgruber, Lukas; Kavunga, Sunil; Cheng, Hsiu-Wei & Nilsen, Ola [Show all 9 contributors for this article] (2024). Electrochemically Assisted Growth of Hopper and Tabular Calcite under Confinement. Crystal Growth & Design. ISSN 1528-7483. 24, p. 4930–4943. doi: 10.1021/acs.cgd.3c01433. Full text in Research Archive Show summary

  Crystallization under confinement is commonplace in nature and offers new pathways to engineer crystals with the desired morphologies in a controlled and reproducible manner. In this work, we demonstrate the electrochemically assisted, in situ formation of hopper and tabular calcite crystals within a wedge-like pore formed by confinement induced by the surface force apparatus (SFA). In this geometry, the distance between the confining surfaces decreases continuously from hundreds of micrometers to a few nanometers in a single experimental setup. Calcium carbonate precipitation followed in real-time is triggered by elevating the pH and thus supersaturation directly inside the pore. The pH increase is tracked with a fluorophore tracer and calculated analytically. The unusual calcite crystal habits are obtained in the absence of precipitation-modifying additives and vary as a function of the distance between the confining walls, where at the largest surface separations, hopper crystals form on the gold surface, whereas flat, tabular calcite forms on mica when the confining distance was below 5 μm. Hexagonal or triangular calcite plates exhibit surfaces dominantly defined by rough (001) planes and increase in their surface area-to-volume ratios with decreasing SFA pore thickness. Stabilization of calcite plates bound by (001) faces is a cooperative effect of the oriented growth of calcite on the confining, negatively charged mica walls and the confinement shape, which promotes the development of calcite morphology in the rapid crystal growth directions. The heterogeneous crystallization of calcite is preceded by the nucleation and spreading of a front composed of submicrometer-sized calcium carbonate particles visualized in situ in the SFA pore. Our work demonstrates abundant crystal growth under nanoscale confinement facilitated by elevated pH and a high surface charge of the confining walls.

• Das, Supti; Brennhagen, Anders; Cavallo, Carmen; Killi, Veronica Anne-Line Kathrine; Jensen, Ingvild Julie Thue & Thøgersen, Annett [Show all 10 contributors for this article] (2024). Directing SEI formation on Si-based electrodes using atomic layer deposition. Chemical Communications. ISSN 1359-7345. 60(100), p. 15011–15014. doi: 10.1039/d4cc05458j. Full text in Research Archive Show summary

  The design of artificial solid eletroctrolyte interphase is an important task to minimize capacity losses in Li-ion batteries. Herein, TiO2 created through atomic layer deposition was used as an artificial SEI on Si nanoparticles. Such coating led to substantial improvement of cycling stability when evaluated with FEC-free electrolyte.

• Øvrebø, Øystein; Lauretis, Angela De; Ma, Qianli; Perale, Giuseppe; Nilsen, Ola & Rossi, Filippo [Show all 7 contributors for this article] (2024). Towards bone regeneration: Understanding the nucleating ability of proline-rich peptides in biomineralisation. Biomaterials Advances. ISSN 2772-9516. 159. doi: 10.1016/j.bioadv.2024.213801. Full text in Research Archive Show summary

  Obtaining rapid mineralisation is a challenge in current bone graft materials, which has been attributed to the difficulty of guiding the biological processes towards osteogenesis. Amelogenin, a key protein in enamel formation, inspired the design of two intrinsically disordered peptides (P2 and P6) that enhance in vivo bone formation, but the process is not fully understood. In this study, we have elucidated the mechanism by which these peptides induce improved mineralisation. Our molecular dynamics analysis demonstrated that in an aqueous environment, P2 and P6 fold to interact with the surrounding Ca2+, PO4 3− and OH− ions, which can lead to apatite nucleation. Although P2 has a less stable backbone, it folds to a stable structure that allows for the nucleation of larger calcium phosphate aggregates than P6. These results were validated experimentally in a concentrated simulated body fluid solution, where the peptide solutions accelerated the mineralisation process compared to the control and yielded mineral structures mimicking the amorphous calcium phosphate crystals that can be found in lamella bone. A pH drop for the peptide groups suggests depletion of calcium and phosphate, a prerequisite for intrinsic osteoinduction, while S/TEM and SEM suggested that the peptide regulated the mineral nucleation into lamella flakes. Evidently, the peptides accelerate and guide mineral formation, elucidating the mechanism for how these peptides can improve the efficacy of P2 or P6 containing devices for bone regeneration. The work also demonstrates how experimental mineralisation study coupled with molecular dynamics is a valid method for understanding and predicting in vivo performance prior to animal trials

• Dahl, Øystein; Sunding, Martin Fleissner; Killi, Veronica Anne-Line Kathrine; Svenum, Ingeborg-Helene; Grandcolas, Mathieu & Andreassen, Magnus [Show all 10 contributors for this article] (2023). Interrogation of the Interfacial Energetics at a Tantalum Nitride/Electrolyte Heterojunction during Photoelectrochemical Water Splitting by Operando Ambient Pressure X-ray Photoelectron Spectroscopy. ACS Catalysis. 13(17), p. 11762–11770. doi: 10.1021/acscatal.3c02423. Full text in Research Archive Show summary

  Photoelectrochemical (PEC) water electrolysis is an important energy conversion (power-to-chemical) method, providing a solution to the intermittent nature of solar energy. However, as PEC systems usually suffer from low operational stability, they are seriously lagging in up-scaled demonstrations and viability. PEC systems are based on semiconductor/liquid interfaces, which have been extensively studied by experiments and theory, but there is a significant knowledge gap in the energetics of such interfaces during operation. In this work, operando ambient pressure X-ray photoelectron spectroscopy (AP-XPS) has been used to characterize the electrical and spectroscopic properties of a pristine Ta3N5 photoelectrode and a Ta3N5/NiOx protection/passivation layer system, which stabilizes an otherwise quickly corroding pristine photoelectrode. We directly observed Fermi-level pinning of Ta3N5 within the applied potential window under both dark and illumination conditions, detrimental to the performance and stability of the photoelectrode. Interestingly, in the Ta3N5/NiOx protection/passivation layer system, the Fermi level gets unpinned under illumination, allowing quasi-Fermi-level splitting and sustaining a significant PEC performance as well as high stability.

• Sannes, Johnny Andreas; Gonano, Bruno; Fjellvåg, Øystein Slagtern; Kumar, Susmit; Nilsen, Ola & Valldor, Björn Martin (2023). X-ray and Neutron Diffraction Studies of SrTe<inf>2</inf>FeO<inf>6</inf>Cl, an Oxide Chloride with Rare Anion Ordering. Inorganic Chemistry. ISSN 0020-1669. 62(32), p. 13081–13088. doi: 10.1021/acs.inorgchem.3c01951. Full text in Research Archive Show summary

  The oxychloride SrTe2FeO6Cl is obtained by high-temperature solid-state synthesis under inert conditions in closed reaction vessels. The compound crystallizes in a novel monoclinic crystal structure that is described in the space group P121/n1 (No. 14). The unit cell parameters, a = 10.2604(1) Å, b = 5.34556(5) Å, c = 26.6851(3) Å, and β = 93.6853(4)°, and atomic parameters were determined from synchrotron diffraction data, starting from a model that was obtained from single-crystal X-ray diffraction data. The anion lattice exhibits a rare ordering of oxide and chloride ions: one-dimensional zig-zag ladders of chlorine (squarelike motif) are surrounded by an oxygen matrix. Two different iron sites coordinated solely to oxygen are present in the structure, one octahedral and one square pyramidal, both distorted. Similarly, two different strontium coordinations are present; the first homoleptic coordinated to eight oxygen atoms and the second heteroleptic coordinated to four oxygen and four chlorine atoms in a fac-like manner. The lone pair of Te(IV) is directed toward the larger chlorine atoms. Magnetic susceptibility measurements confirm that Fe is +3 (d5) in the high-spin electronic configuration, exhibiting an almost ideal spin-only moment, μeff = 5.65 μB Fe–1. The slightly negative Weiss constant (θCW = −39 K) suggests dominating antiparallel spin-to-spin coupling in the paramagnetic temperature range, agreeing with an observed long-range antiferromagnetic spin ordering below Néel temperature, TN ∼ 13 K, and a broad second order-like anomaly in the specific heat measurement data. Low-temperature neutron diffraction data reveal that the antiferromagnetic ordered phase is C-type, with a k-vector (1/2, 1/2, 0) and ordered moment of 4.14(7) μB. The spin structure can be described as antiferromagnetic ordered layers stacked along the a-axis, forming layers of squares that alternate along the c-axis.

• Hansen, Per-Anders Stensby; Sørensen, Silje Holm; Desbois, Nicolas; Gros, Claude P. & Nilsen, Ola (2023). Perylenes, Porphyrins, and Other Large Dye Molecules for Molecular Layer Deposition. Advanced Materials Interfaces. doi: 10.1002/admi.202300667. Full text in Research Archive Show summary

  Abstract Molecular layer deposition (MLD) is an incredibly powerful and flexible tool for designing completely new materials with novel and unique properties. The low temperature layer‐by‐layer approach and the use of highly reactive reactants allows one to combine vastly different organic and inorganic species and construct nanostructures with subnanometer precision. If not limited by the volatility of the reactants involved, the possibilities will be endless. This is most notable for the organic building blocks where an overall low volatility severely limits the toolbox of large molecules with interesting optical and electrical properties such as red‐ox activity and optical conversion. In this work, different strategies for molecular design of large molecules are investigated that allow vaporization while still having the necessary reactivity for MLD growth. Using these strategies, film growth with perylene and porphyrin derivatives, both molecules well known for their functional and optical properties are successfully achieved. With this knowledge, there is an opening to include much larger and more complex organic molecules into the world of vapor phase chemistry.

• Nøvik, Steffen; Drageseth, Magnus Flø; Grøndalen, Magnus Børresen; Nilsen, Ola; Krauss, Stefan Johannes Karl & Martinsen, Ørjan Grøttem [Show all 7 contributors for this article] (2022). A CMOS Multi-Electrode Array for Four-Electrode Bioimpedance Measurements. IEEE Transactions on Biomedical Circuits and Systems. ISSN 1932-4545. 16(6), p. 1276–1286. doi: 10.1109/TBCAS.2022.3214243. Full text in Research Archive Show summary

  This work demonstrates how a multi-electrode array (MEA) dedicated to four-electrode bioimpedance measurements can be implemented on a complementary metal–oxide–semiconductor (CMOS) chip. As a proof of concept, an 8 × 8 pixel array along with dedicated amplifiers was designed and fabricated in the TSMC 180 nm process. Each pixel in the array contains a circular current carrying (CC) electrode that can act as a current source or sink. In order to measure a differential voltage between the pixels, each CC electrode is surrounded by a ring shaped pick up (PU) electrode. The differential voltages can be measured by an on-board instrumentation amplifier, while the currents can be measured with an on-bard transimpedance amplifier. Openings in the passivation layer exposed the aluminum top metal layer, and a metal stack of zinc, nickel and gold was deposited in an electroless plating process. The chips were then wire bonded to a ceramic package and prepared for wet experiments by encapsulating the bonding wires and pads in the photoresist SU-8. Measurements in liquids with different conductivities were performed to demonstrate the functionality of the chip.

• Hansen, Per-Anders Stensby; Svendsen, Joachim; Nesteng, Hanne Martinsen & Nilsen, Ola (2022). Aromatic sensitizers in luminescent hybrid films. RSC Advances. 12(28), p. 18063–18071. doi: 10.1039/d2ra03360g. Full text in Research Archive Show summary

  Atomic layer deposition offers a unique set of design possibilities due to the vast range of metal and organic precursors that can be used and combined. In this work, we have combined lanthanides with aromatic aids as strongly absorbing sensitizers to form highly luminescent thin films. Terephthalic acid is used as a base sensitizer, absorbing shorter wavelengths than 300 nm. The absorption range is extended towards the near-UV and blue range by increasing the aromatic system and adding functional groups that have strong red-shifting effects. While terbium and europium provide green and red emission, yttrium allows emission from the sensitizer itself spanning the whole color range from purple, blue and green to red. Many organic dye molecules show very high luminescence quantum yields and several of the molecules and materials investigated in this work show bright luminescence.

• Sønsteby, Henrik Hovde; Killi, Veronica Anne-Line Kathrine; Rykkje, Linn Margrethe; Bickford, Justin R.; Martin, Eric G. & Hoffman, Robert C. [Show all 7 contributors for this article] (2022). Avoiding water reservoir effects in ALD of functional complex alkali oxides by using O<inf>3</inf> as the oxygen source. Dalton Transactions. ISSN 1477-9226. 51(3), p. 927–934. doi: 10.1039/d1dt03960a. Full text in Research Archive Show summary

  A new ozone-based route for excellent control of complex alkali oxides by ALD.

• Nematzadeh, Mozhdeh; Nilsen, Ola; Häfliger, Philipp & Killi, Veronica Anne-Line Kathrine (2022). Investigation of the Atomic Layer Deposition of the Titanium Dioxide (TiO2) Film as pH Sensor Using a Switched Capacitor Amplifier. Chemosensors. 10(7). doi: 10.3390/chemosensors10070274. Full text in Research Archive Show summary

  The electrical and chemical properties of the titanium dioxide (TiO2) coated spirals grown by the atomic layer deposition (ALD) technique in two different temperatures of 150 °C and 300 °C are studied. The thickness of the TiO2 layers studied are 20, 40, and 80 nm. A switched capacitor amplifier is used to investigate the pH response and the capacitance of the samples. It is found that the performance of the TiO2 samples depends on either the thickness or the deposition temperature due to the differences in the physical properties of the oxide layer such as surface roughness and film density. The high temperature samples are more crystalline, whereas the low temperature samples are more amorphous. Since there is a low pass filter effect in the electrolyte–sample interface, the TiO2 coated samples show the better response to the pH change for the high temperature samples as the sensor surface area for binding the hydrogen ions is larger and the charge transfer resistance is smaller. Furthermore, more roughness on the surface can be obtained by increasing the thickness, which reduces the charge transfer resistance. In this study, the 80 nm sample deposited at 300 °C gives the best pH response of 40 mV/pH.

• Rogowska, Melania; Bruzell, Ellen Merete; Valen, Håkon & Nilsen, Ola (2022). Photoactive Zr-aromatic hybrid thin films made by molecular layer deposition. RSC Advances. 12(25), p. 15718–15727. doi: 10.1039/d2ra02004a. Full text in Research Archive Show summary

  The principle of antimicrobial photodynamic therapy (PDT) is appealing because it can be controlled by an external light source and possibly the use of durable materials. However, to utilise such surfaces requires a process for their production that allows for coating on even complex geometries. We have therefore explored the ability of the emerging molecular layer deposition (MLD) technique to produce and tune PDT active materials. This study demonstrates how the type of aromatic ligand influences the optical and antimicrobial properties of photoactive Zr-organic hybrid thin films made by MLD. The three aromatic dicarboxylic acids: 2,5-dihydroxy-1,4-benzenedicarboxylic acid, 2-amino-1,4-benzenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid have been combined with ZrCl4 to produce hybrid coatings. The first system has not been previously described by MLD and is therefore more thoroughly investigated using in situ quartz crystal microbalance (QCM), Fourier transform infrared (FTIR) and UV-Vis spectroscopy. The antibacterial phototoxic effects of Zr-organic hybrids have been explored in the Staphylococcus aureus bacteria model using a UVA/blue light source. Films based on the 2,6-naphthalenedicarboxylic acid linker significantly reduced the number of viable bacteria by 99.9%, while no apparent activity was observed for the two other photoactive systems. Our work thus provides evidence that the MLD technique is a suitable tool to produce high-quality novel materials for possible applications in antimicrobial PDT, however it requires a careful selection of aromatic ligands used to construct photoactive materials.

• Rogowska, Melania; Hansen, Per-Anders Stensby; Sønsteby, Henrik Hovde; Dziadkowiec, Joanna; Valen, Håkon & Nilsen, Ola (2021). Molecular layer deposition of photoactive metal-naphthalene hybrid thin films. Dalton Transactions. ISSN 1477-9226. 50(37), p. 12896–12905. doi: 10.1039/d1dt02201f. Full text in Research Archive Show summary

  We here report on photoactive organic–inorganic hybrid thin films prepared by the molecular layer deposition (MLD) method. The new series of hybrid films deposited using 2,6-naphthalenedicarboxylic acid (2,6-NDC) and either hafnium chloride (HfCl4), yttrium tetramethylheptanedionate (Y(thd)3) or titanium chloride (TiCl4) were compared with the known zirconium chloride (ZrCl4) based system. All metal-naphthalene films are amorphous as-deposited and show self-saturating growth as expected for an ideal MLD process with varied growth rates depending on the choice of metal precursor. The growth was studied in situ using quartz crystal microbalance (QCM) and the films were further characterised using spectroscopic ellipsometry (SE), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and UV-Vis and photoluminescence (PL) spectroscopy to obtain information on their physicochemical properties. The hybrid thin films display intense blue photoluminescence, except for the Ti-organic complex in which titanium clusters were found to be an effective PL quencher for the organic linker. We demonstrate how the optical properties of the films depend on the choice of metal component to make a foundation for further studies on these types of organic–inorganic hybrid materials for applications as photoactive agents.

• Sønsteby, Henrik Hovde; Skaar, Erik; Fjellvåg, Helmer & Nilsen, Ola (2021). Effect of Subcycle Arrangement on Direct Epitaxy in ALD of LaNiO3. ACS Applied Electronic Materials. 3(1), p. 292–298. doi: 10.1021/acsaelm.0c00855. Full text in Research Archive Show summary

  Monolithic device integration of crystalline complex oxide thin films can open for smarter and more sustainable devices in electronics and energy technology. However, the facile integration of such compounds has so far been incompatible with the present production lines for electronics. Atomic layer deposition (ALD) is already well-integrated for the production of amorphous binary oxides in electronics, but extending the technique to crystalline complex compounds has proved challenging. Herein, we show how the subcycle arrangement (i.e., the overall order of binary subcycles) plays a crucial role in the formation and quality of crystalline complex oxides by ALD, exemplified by the growth of LaNiO3. We show that an approach somewhere in between the traditional homogeneous and multilayer approaches provides the best platform for crystalline growth. Based on these results, we hypothesize that choosing multilayer unit slab thicknesses close to the interlayer distances in the target crystalline structure, while still maintaining the correct cation composition, enhances as-deposited crystallinity and in turn the functional properties. We believe this approach can be used to extend the toolbox of attainable crystalline complex oxides by ALD and establish utilization of the technique for monolithic integration of functional thin films.

• Gorzkowska-Sobas, Agnieszka A; Lausund, Kristian Blindheim; Koning, Martijn de; Petrovic, Veljko; Chavan, Sachin Maruti & Smith, Martin W. [Show all 7 contributors for this article] (2021). Utilizing Zirconium MOF-functionalized fiber substrates prepared by molecular layer deposition for toxic gas capture and chemical warfare agent degradation. Global Challenges. 5(12). doi: 10.1002/gch2.202100001. Full text in Research Archive Show summary

  Metal–organic frameworks (MOFs) are a class of porous organic-inorganic solids extensively explored for numerous applications owing to their catalytic activity and high surface area. In this work MOF thin films deposited in a one-step, molecular layer deposition (MLD), an all-gas-phase process, on glass wool fibers are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and their capabilities towards toxic industrial chemical (TIC) capture and chemical warfare agents (CWA) degradation are investigated. It is shown that despite low volume of the active material used, MOFs thin films are capable of removal of harmful gaseous chemicals from air stream and CWA from neutral aqueous environment. The results confirm that the MLD-deposited MOF thin films, amorphous and crystalline, are suitable materials for use in air filtration, decontamination, and physical protection against CWA and TIC.

• Kvamme, Kristian; Ruud, Amund; Weibye, Kristian; Sajavaara, Timo & Nilsen, Ola (2021). Phosphites as precursors in atomic layer deposition thin film synthesis. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. ISSN 0734-2101. 39(3). doi: 10.1116/6.0000844. Full text in Research Archive Show summary

  We here demonstrate a new route for deposition of phosphorous based materials by atomic layer deposition (ALD) using the phosphites Me3PO3 or Et3PO3 as precursors. These contain phosphorous in the oxidation state (III) and are open for deposition of reduced phases by ALD. We have investigated their applicability for the synthesis of LiPO and AlPO materials and characterized their growth by means of in situ quartz crystal microbalance. Phosphites are good alternatives to the established phosphate-based synthesis routes as they have high vapor pressure and are compatible with water as a coreactant during deposition. The deposited materials have been characterized using XPS, x-ray fluorescence, and ion beam analysis for composition analysis, spectroscopic ellipsometry for thickness, and FTIR for local structure.

• Hansen, Per-Anders Stensby & Nilsen, Ola (2021). Quinizarin: a large aromatic molecule well suited for atomic layer deposition. Dalton Transactions. ISSN 1477-9226. 50(24), p. 8307–8313. doi: 10.1039/d1dt00683e. Full text in Research Archive Show summary

  Atomic layer deposition (ALD) is a remarkable synthesis tool due to the vast array of materials that can be deposited and the complexity of structures that can be designed. The low-temperature layer-by-layer approach even allows organic and inorganic components to be combined as hybrid or composite materials. The technique is then called molecular layer deposition (MLD). This opens the door for deposition of advanced optical materials using highly absorbing aromatic molecules. Unfortunately, most large aromatic molecules are difficult to sublime or have insufficient reactivity. This is a major barrier for ALD when designing with the use of organic components for dye-sensitized solar cells, luminescence, visible light photochemistry, chemical sensors and organic electronics. In this work, we introduce a well-known orange dye molecule, quinizarin. This molecule has a large conjugated aromatic system with strong absorption of visible light and shows strong luminescence both in solutions and as a complex together with aluminium ions. Interestingly, quinizarin also shows surprisingly good properties for film deposition due to reactive –OH groups and low sublimation temperature (130 °C). Strongly coloured pink hybrid films were deposited with trimethylaluminium and quinizarin at 175 °C with a growth rate of 0.28 nm per cycle. These films were not luminescent although their optical absorption spectra are similar to those of the corresponding solution. An attempt was made to dilute quinizarin through partial replacement with pentaerythritol as a multilayer structure or simultaneous co-pulsing, although this also did not produce luminescent films. The low sublimation temperature, good reactivity and large conjugated system of quinizarin open the way for exploration of solid-state hybrid and organic films based on this molecule along many different technological pathways.

• Sønsteby, Henrik Hovde; Skaar, Erik; Fjellvåg, Øystein; Bratvold, Jon E.; Fjellvåg, Helmer & Nilsen, Ola (2020). A foundation for complex oxide electronics -low temperature perovskite epitaxy. Nature Communications. 11(1). doi: 10.1038/s41467-020-16654-2. Full text in Research Archive Show summary

  As traditional silicon technology is moving fast towards its fundamental limits, all-oxide electronics is emerging as a challenger offering principally different electronic behavior and switching mechanisms. This technology can be utilized to fabricate devices with enhanced and exotic functionality. One of the challenges for integration of complex oxides in electronics is the availability of appreciable low-temperature synthesis routes. Herein we provide a fundamental extension of the materials toolbox for oxide electronics by reporting a facile route for deposition of highly electrically conductive thin films of LaNiO3 by atomic layer deposition at low temperatures. The films grow epitaxial on SrTiO3 and LaAlO3 as deposited at 225 °C, with no annealing required to obtain the attractive electronic properties. The films exhibit resistivity below 100 µΩ cm with carrier densities as high as 3.6 · 1022 cm−3. This marks an important step in the realization of all-oxide electronics for emerging technological devices.

• Kjeldstad, Torunn; Thøgersen, Annett; Stange, Marit Synnøve Sæverud; Jensen, Ingvild Julie Thue; Nilsen, Ola & Galeckas, Augustinas [Show all 7 contributors for this article] (2020). Selective etching of nanostructured a-Si:Al and its effect on porosity, Al gradient and surface oxidation. Thin Solid Films. ISSN 0040-6090. 702. doi: 10.1016/j.tsf.2020.137982. Full text in Research Archive Show summary

  Nanoporous amorphous silicon (a-Si) with <5 nm cylindrical pores have been fabricated by phase separation of aluminum (Al) and silicon, forming self-assembled Al nanowires (NWs), followed by subsequent removal of Al by wet etching. This work studies the removal process of the Al NWs when using the different etchants HCl, H3PO4, and H2SO4. Total reflectance measurements are used in combination with theoretical modeling to estimate the lateral gradient of Al concentration formed during the etching process. X-ray Photoelectron Spectroscopy is used to show that the choice of Al etching agent has implications for the surface states of the remaining a-Si matrix. We have found that H3PO4 is the most efficient etching agent, while HCl provides a less oxidized a-Si matrix in addition to the least reflective surface. By varying the etching agent, the degree of surface oxidation and shape of Al gradient throughout the film can be tuned.

• Sønsteby, Henrik Hovde; Skaar, Erik; Bratvold, Jon Einar; Freeland, John W.; Yanguas-Gil, Angel & Elam, Jeffrey W. [Show all 8 contributors for this article] (2020). Tuning electronic properties in LaNiO3 thin films by B-site Cu-substitution. Journal of Materials Chemistry C. ISSN 2050-7526. 8(36), p. 12662–12668. doi: 10.1039/D0TC03406A. Full text in Research Archive
• Sønsteby, Henrik Hovde; Killi, Veronica Anne-Line Kathrine; Storaas, Thomas Aarflot; Choudhuy, Devika; Elam, Jeffrey W. & Fjellvåg, Helmer [Show all 7 contributors for this article] (2020). Understanding KOtBu in atomic layer deposition–in situ mechanistic studies of the KNbO3 growth process. Dalton Transactions. ISSN 1477-9226. 49(38), p. 13233–13242. doi: 10.1039/D0DT02324H. Full text in Research Archive
• Cheng, Chaoqun; Akram, Muhammad Nadeem; Nilsen, Ola; Pryds, Nini & Wang, Kaiying (2020). Solar-driven plasmonic heterostructure Ti/TiO2−x with gradient doping for sustainable plasmon-enhanced catalysis. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 22(15), p. 7769–7777. doi: 10.1039/d0cp00672f. Full text in Research Archive Show summary

  Plasmon-enhanced harvesting of photons has contributed to the photochemical conversion and storage of solar energy. However, high dependence on noble metals and weak coupling in heterostructures constrain the progress towards sustainable plasmonic enhancement. Here earth-abundant Ti is studied to achieve the plasmonic enhancement of catalytic activity in a solar-driven heterostructure Ti/TiO2−x. The heterostructure was fabricated by engineering an intense coupling of a surface-etched Ti metal and a gradient-based TiO2−x dielectric via diffusion doping. Ti/TiO2−x exhibits a highly resonant light absorption band associated with surface plasmon resonances that exhibit strong near-field enhancement (NFE) and hot electron injection effects. In a photoelectrochemical system, intense interaction of the resonant plasmons with a vicinal TiO2−x dielectric accelerates the transfer of solar energy to charge carriers for plasmon-enhanced water splitting reactions. Moreover, the plasmonic Ti/TiO2−x structure presents sustained enhanced redox activities over 100 h. The intense coupling by gradient doping offers an effective approach to enable the plasmon resonances of Ti excited by visible light. The Ti-based plasmonic heterostructure potentially opens an alternative avenue towards sustainable plasmon-enhanced catalysis.

• Kvalvik, Julie Nitsche; Hansen, Per-Anders Stensby & Nilsen, Ola (2020). Design of experiments approach to luminescent CaMoO4 by atomic layer deposition. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. ISSN 0734-2101. 38, p. 052408–052408. doi: 10.1116/6.0000327. Full text in Research Archive Show summary

  Atomic layer deposition (ALD) is evolving beyond binary compounds to complex oxides and doped structures, taking advantage of the nanometer precision ALD provides. In practice, the development of complex ALD-processes usually means performing many ALD-runs, as success at first attempt is unlikely. One factor at a time methods, where only one factor is altered and the rest are kept constant, are most often chosen due to their intuitive communication of control. However, they do have several drawbacks, being slow, neglecting secondary effects, and are usually not randomized—meaning that errors that arise over time can easily be overlooked. We here dig into our statistical toolbox and show how design of experiments (DoE) can be used to efficiently develop an ALD-process to deposit crystalline, luminescent CaMoO4—a proposed material for optoelectronic applications, like light emitting diodes or as a host for solar down-converters. Using DoE enables screening for a wider range of deposition temperatures, pulsed composition, and annealing parameters, by only performing nine ALD-runs in our case. We moreover look into how these parameters affect crystallinity, composition, and the photoluminescence properties and use DoE to show which factors have the greatest effects on these properties. The work also lays out the basic theory of the DoE-field and how to implement DoE in developing ALD-processes, in general, to ease the usage of DoE for the ALD-community.

• Ellingsen, Josef Gert Åsheim; Venkatachalapathy, Vishnukanthan; Azarov, Alexander; Nilsen, Ola & Kuznetsov, Andrej (2020). Al incorporation during metal organic chemical vapour deposition of aluminium zinc oxide. Thin Solid Films. ISSN 0040-6090. 709. doi: 10.1016/j.tsf.2020.138245. Full text in Research Archive Show summary

  Aluminium zinc oxide (AZO) is a promising transparent conductive oxide this is difficult to fabricate by metal-organic chemical vapour deposition (MOCVD) because of prereactions between the precursors for Al and oxygen. One way of reducing prereactions is to use separate injectors. In this work, we investigated the effect of separate injectors and various flow configurations on the MOCVD fabrication of AZO using diethyl zinc (DEZn), tert-butanol (tBuOH), and trimethyl aluminium (TMAl) precursors. X-ray diffraction revealed that the resulting films maintained a purely wurtzite ZnO structure, and that the Al incorporation changed the c lattice parameters from 5.207 to 5.181 Å in agreement with theoretical models of mixing on the Zn sub-lattice. This indicates that Al was mainly incorporated onto the Zn sub-lattice. The maximum Al concentration was 6 × 1021 cm . The Al concentration was directly influenced by the TMAl flow rates, but the incorporation efficiency of Al also depended on the O/Zn balance as determined by the tBuOH supply and the total flow rate through the TMAl+DEZn injector. The tBuOH supply decreased the incorporation efficiency, while it increased for higher total flow in the TMAl+DEZn injector although both changes nominally increases the O/Zn balance. This dual, but contradicting, dependency on the O/Zn suggested that the incorporation efficiency depended not only on precursor supply, but also on the chemical stability of the Al species present at the growth interface. The concept of a reaction depth of TMAl was introduced to discuss the observed trends, and a qualitative model was suggested to explain how the Al-species present at the growth interface are determined by the relative depths of the reaction depth and the boundary layer. These findings illustrate the limits of the O/Zn parameter when using separate injectors because the properties of the boundary layer can affect Al incorporation during MOCVD growth. This should be relevant for MOCVD growth of other compound semiconductor systems that are grown using separate injectors.

• Duparc, Marion Jeanne Louise; Sønsteby, Henrik Hovde; Nilsen, Ola; Sjåstad, Anja Olafsen & Fjellvåg, Helmer (2020). Atomic Layer Deposition of GdCoO3 and Gd0.9Ca0.1CoO3. Materials. 13(1), p. 1–10. doi: 10.3390/ma13010024. Full text in Research Archive Show summary

  Thin films of the catalytically interesting ternary and quaternary perovskites GdCoO3 and Gd0.9Ca0.1CoO3 are fabricated by atomic layer deposition using metal β-diketonates and ozone as precursors. The resulting thin films are amorphous as deposited and become single-oriented crystalline on LaAlO3(100) and YAlO3(100/010) after post-annealing at 650 °C in air. The crystal orientations of the films are tunable by choice and the orientation of the substrate, mitigated through the interface via solid face epitaxy upon annealing. The films exhibit no sign of Co2+. Additionally, high-aspect-ratio Si(100) substrates were used to document the suitability of the developed process for the preparation of coatings on more complex, high-surface-area structures. We believe that coatings of GdCoO3 and Gd1−xCaxCoO3 may find applications within oxidation catalysis.

• Sønsteby, Henrik Hovde; Bratvold, Jon Einar; Killi, Veronica Anne-Line Kathrine; Choudhury, Devika; Elam, Jeffrey W. & Fjellvåg, Helmer [Show all 7 contributors for this article] (2020). tert-butoxides as precursors for atomic layer deposition of alkali metal containing thin films. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. ISSN 0734-2101. 38, p. 1–15. doi: 10.1116/6.0000589. Full text in Research Archive Show summary

  Alkali metal containing materials have become increasingly attractive in a world hunting for sustainable energy materials and green functional devices. Lithium- and sodium battery technology, lead-free piezo- and ferroelectric devices, and record-breaking alkali doped tandem perovskite solar cells are among the applications where alkali metal-containing thin films get increasing attention. Atomic layer deposition (ALD) is one of the enabling thin film deposition techniques that offer chemical and geometrical versatility to realize the implementation of such thin films on an applicable scale. The drawback has until recently been a lack of available precursor chemistry that offers self-limiting growth that is fundamental to ALD. The alkali metal tert-butoxides have been shown to exhibit the necessary properties to facilitate saturating growth for Li-, Na-, K-, and Rb-containing compounds. However, the behavior of the tert-butoxides in ALD-growth has been considered difficult to unravel, with processes exhibiting limited control and low reproducibility. Very little has been reported on trends in reaction mechanisms as the mass of the alkali metal increases. Herein, we summarize the existing literature on the use of alkali metal tert-butoxides as precursors in ALD. We consider differences in the structure and behavior of the tert-butoxides as the alkali metal cation becomes heavier. In addition, we present precursor synthesis routes and key information on precursor structure, stability, and mechanistic behavior. Finally, we provide the first ever report of Cs-containing films by ALD to complement previous work on its lighter counterparts.

• Kvalvik, Julie Nitsche; Kvamme, Kristian Breivik; Almaas, Kjetil; Ruud, Amund; Sønsteby, Henrik Hovde & Nilsen, Ola (2020). LiF by atomic layer deposition—Made easy. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. ISSN 0734-2101. 38(5), p. 1–4. doi: 10.1116/6.0000314. Full text in Research Archive Show summary

  Lithium fluoride (LiF) is an integral part of UV optics. Recently, it has also gained attention for its role in the solid-electrolyte interphase on the anode of lithium-ion batteries. Atomic layer deposition (ALD) is the preferred tool for synthesizing conformal and pin-hole free LiF thin films, especially on high aspect ratio structures. Present routes to deposit LiF by ALD are based on HF or HF-pyridine as the fluorine source, requiring strict safety precautions. Other routes involve TiF4 or WF6, resulting in inclusions of Ti or W impurities in the resulting films. Herein, we present a new route to deposit LiF by ALD, using lithium tert-butoxide (LiOtBu) and NH4F as precursors. The process yields uniform films over a broad temperature range (150–300 °C), with a growth per cycle of 50.9 pm/cycle (225 °C). The films are free from any nitrogen contamination from the NH4F precursor. This process provides a facile route for high purity LiF thin films with the use of less harmful precursor chemistry.

• Lausund, Kristian Blindheim; Olsen, Malin; Hansen, Per-Anders Stensby; Valen, Håkon & Nilsen, Ola (2020). MOF thin films with bi-aromatic linkers grown by molecular layer deposition. Journal of Materials Chemistry A. ISSN 2050-7488. 8(5), p. 2539–2548. doi: 10.1039/c9ta09303f. Full text in Research Archive Show summary

  Thin films of metal–organic frameworks (MOFs) are promising for a wide range of applications including membranes for separations and sensor materials in microelectronics. Growth of such thin films using atomic/molecular layer deposition (ALD/MLD) has recently been demonstrated; however, the range of examples is still narrow. Here, we expand the repertory of gas-phase MOF thin film synthesis by ALD/MLD to include 2,6-naphthalenedicarboxylate (2,6-NDC) and biphenyl-4,4′-dicarboxylate (BP-4,4′-DC) as organic linkers. The films, which were deposited using ZrCl4 and either H2–2,6-NDC or H2–BP-4,4′-DC, were amorphous and formed crystalline MOF-structures when treated with acetic acid vapour at 160 °C. The film growth was investigated using in situ quartz crystal microbalance (QCM) measurements, and was in addition characterized using spectroscopic ellipsometry (SE), photoluminescence (PL), scanning electron microscopy (SEM), grazing incidence X-ray diffraction (GIXRD) and X-ray reflectivity (XRR). We further performed introductory investigations into a selection of possible future applications of these films, due to their porosity, luminescent and antibacterial properties. Expanding the repertory of MOF synthesis by ALD/MLD to include longer linkers such as 2,6-NDC and BP-4,4′-DC enables synthesis of thin films with a larger range of pore sizes.

• Hansen, Per-Anders Stensby; Zikmund, Tomas; Yu, Ting; Kvalvik, Julie Nitsche; Aarholt, Thomas & Prytz, Øystein [Show all 8 contributors for this article] (2020). Single-step approach to sensitized luminescence through bulk-embedded organics in crystalline fluorides. Communications chemistry. 3. doi: 10.1038/s42004-020-00410-0. Full text in Research Archive Show summary

  Abstract Luminescent materials enable warm white LEDs, molecular tagging, enhanced optoelectronics and can improve energy harvesting. With the recent development of multi-step processes like down- and upconversion and the difficulty in sensitizing these, it is clear that optimizing all properties simultaneously is not possible within a single material class. In this work, we have utilized the layer-by-layer approach of atomic layer deposition to combine broad absorption from an aromatic molecule with the high emission yields of crystalline multi-layer lanthanide fluorides in a single-step nanocomposite process. This approach results in complete energy transfer from the organic molecule while providing inorganic fluoride-like lanthanide luminescence. Sm 3+ is easily quenched by organic sensitizers, but in our case we obtain strong fluoride-like Sm 3+ emission sensitized by strong UV absorption of terephthalic acid. This design allows combinations of otherwise incompatible species, both with respect to normally incompatible synthesis requirements and in controlling energy transfer and quenching routes.

• Kvalvik, Julie Nitsche; Borgersen, Jon; Hansen, Per-Anders Stensby & Nilsen, Ola (2020). Area-selective atomic layer deposition of molybdenum oxide. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. ISSN 0734-2101. 38(4), p. 042406-1–042406-9. doi: 10.1116/6.0000219. Full text in Research Archive Show summary

  Area-selective bottom-up synthesis routes of thin films are required to overcome the current limits in lithography, and such growth can be achieved with high quality and nanometer thickness control by area-selective atomic layer deposition (AS-ALD). However, the current range of materials demonstrated deposited by AS-ALD is limited, and no processes for molybdenum oxide have been available so far. In this work, the authors explore the properties of a new ALD precursor, MoCl4O, for deposition of molybdenum oxides by ALD. MoCl4O is administered at room temperature during deposition, making it readily available for use. When reacted with a combination of water and ozone, it leads to an AS-ALD process for deposition of MoOx—the first reported. The process is perfectly selective for growth on glass as compared to Si(100) substrates for deposition temperatures between 200 and 300 °C, with a growth rate of 0.72 Å/cycle at 300 °C. The process is attempted on a range of substrates proving good growth on soda-lime glass and LiF and no growth on Si(100), silica, Na2CO3, CaCO3, Li3PO3, or Li2SiO3. The findings of this study indicate an activated process by diffusion of sodium or lithium through the film during growth. The obtained films have further been characterized by x-ray photoelectron spectroscopy, scanning electron microscopy, x-ray diffraction, and atomic force microscopy, revealing films with an RSM roughness of 23 nm with the presence of crystalline MoO2 (C P/m) when deposited at 300 °C and crystalline Mo9O26 when deposited at 250 °C. The rough MoOx thin films may be applicable for electrocatalysis, gas sensors, or lithium-ion batteries. The findings of this study enable AS-ALD synthesis of molybdenum oxide with excellent selectivity not dependent on intermittent etching cycles during growth.

• Hu, Yang; Miikkulainen, Ville; Mizohata, Kenichiro; Norby, Truls Eivind; Nilsen, Ola & Fjellvåg, Helmer (2020). Ionic conductivity in LixTaOy thin films grown by Atomic Layer Deposition (ALD). Electrochimica Acta. ISSN 0013-4686. 361. doi: 10.1016/j.electacta.2020.137019. Full text in Research Archive Show summary

  The material system Li-Ta-O is a promising candidate for thin-film solid-state electrolytes in Li-ion batteries. In the present study, we have varied the Li content x in LixTaOy thin films grown by atomic layer deposition (ALD) with the aim of improving the Li-ion conductivity. The amorphous films were grown at 225 °C on insulating sapphire and on conductive Ti substrates using tantalum ethoxide (Ta(OEt)5), lithium tert-butoxide (LiOtBu) and water as reactants. The film composition was determined by time-of-flight elastic recoil detection analysis (TOF-ERDA), displaying an almost linear relationship between the pulsed and deposited Li content. The ionic conductivities were determined by in-plane and cross-plane AC measurements, exhibiting an Arrhenius-type behaviour and comparatively weak thickness-dependence. Increasing Li content x from 0.32 to 0.98 increases the film conductivity by two orders of magnitude while higher Li content x = 1.73 results in decreased conductivity. A room-temperature conductivity σRT of ~10−8 S cm−1 is obtained for a 169 nm thick Li0.98TaOy film. The evolution of conductivity and activation energy suggests a competing effect between the concentration and the mobility of mobile Li ions when more Li are incorporated. The compositional dependence of Li transport mechanism is discussed.

• Brennhagen, Anders; Kvamme, Kristian Breivik; Sverdlilje, Katja S. S. & Nilsen, Ola (2020). High power iron phosphate cathodes by atomic layer deposition. Solid State Ionics. ISSN 0167-2738. 353. doi: 10.1016/j.ssi.2020.115377. Full text in Research Archive Show summary

  Amorphous thin films of FePO4 and Fe4(P2O7)3 show excellent power capabilities and good stability as cathode materials in Li-ion batteries. Within our tested range of materials, 10 nm FePO4 shows the best results and can handle specific powers above 1 MW/kg. The thin films are deposited using atomic layer deposition (ALD) and we studied the growth using in situ quartz crystal microbalance (QCM) showing self-limiting growth. Their electrochemical properties were characterized as cathode materials in coin cell batteries using cyclic voltammetry (CV) and galvanostatic cycling (GC), correcting for the roughness of the substrates and addressing contributions from non-Faradaic processes.

• Fjellvåg, Øystein; Ruud, Amund; Sønsteby, Henrik Hovde; Nilsen, Ola & Fjellvåg, Helmer (2020). Crystallization, Phase Stability, and Electrochemical Performance of β-MoO3 Thin Films. Crystal Growth & Design. ISSN 1528-7483. 20(6), p. 3861–3866. doi: 10.1021/acs.cgd.0c00156. Full text in Research Archive Show summary

  Insight into the crystallization process of functional materials deposited as thin films in an amorphous state is essential when phase pure samples of specific polymorphs are sought for utilization of performance aspects or fundamental studies. In this work, we report on controlled crystallization of α- and β-MoO3 polymorphs from amorphous MoO3 thin films produced by atomic layer deposition (ALD). The MoO3 films are amorphous as deposited. Our experiments show that β-MoO3 starts to crystallize from amorphous MoO3 at a surprisingly low temperature of 185 °C, only 20 °C above the adopted ALD deposition temperature. Thin films of the β-MoO3 polymorph start to slowly convert into α-MoO3 at temperatures above 300 °C; however, long holding times are required to obtain phase pure products. High-quality thin film samples (electrodes) were characterized by electrochemical cycling toward lithium, demonstrating that α- and β-MoO3 transfers into the same chemical state during cycling and that amorphous MoO3 undergoes less change upon cycling.

• Bratvold, Jon E.; Fjellvåg, Helmer & Nilsen, Ola (2020). Phase and Orientation Control of NiTiO3 Thin Films. Materials. 13(1), p. 1–19. doi: 10.3390/ma13010112. Full text in Research Archive Show summary

  Subtle changes in the atomic arrangement of NiTiO3 in the ilmenite structure affects its symmetry and properties. At high temperatures, the cations are randomly distributed throughout the structure, resulting in the corundum structure with R−3c symmetry. Upon cooling, the cations order in alternating layers along the crystallographic c axis, resulting in the ilmenite structure with R−3 symmetry. Related to this is the R3c symmetry, where the cations alternate both perpendicularly and along the c axis. NiTiO3 with the latter structure is highly interesting as it exhibits ferroelectric properties. The close relationship between structure and properties for ilmenite-related structures emphasizes the importance of being able to control the symmetry during synthesis. We show that the orientation and symmetry of thin films of NiTiO3 formed by atomic layer deposition (ALD) can be controlled by choice of substrate. The disordered phase (R−3c), previously only observed at elevated temperatures, have been deposited at 250 °C on α-Al2O3 substrates, while post-deposition annealing at moderate temperatures (650 °C) induces ordering (R−3). We have in addition explored the symmetry and epitaxial orientation obtained when deposited on substrates of LaAlO3(100), SrTiO3(100) and MgO(100). The presented work demonstrates the possibilities of ALD to form metastable phases through choice of substrates.

• Bratvold, Jon E.; Sønsteby, Henrik Hovde; Nilsen, Ola & Fjellvåg, Helmer (2019). Control of growth orientation in as-deposited epitaxial iron-rich nickel ferrite spinel. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. ISSN 0734-2101. 37(2), p. 1–7. doi: 10.1116/1.5082012. Full text in Research Archive Show summary

  The authors here report epitaxial growth of the ferrimagnet NixFe3–xO4 (NFO) by atomic layer deposition at low temperatures. Films grow epitaxially at a reactor temperature of 250 °C and require no further postannealing treatment. (100)-, (110)-, and (111)-oriented thin films of NFO are attainable by using MgO (100)/LaAlO3 (100), LaAlO3 (110), and Al2O3 (001) substrates, respectively. This means that the direction of the easy axis of magnetization relative to the film surface can be selected by the choice of substrate. The authors carefully study nucleation onset and growth dynamics by varying the number of cycles used to deposit the films. This shows that the initial growth is mostly inhibited by the Fe-species, creating a small composition gradient for the first few nanometers of the film. The growth rate varies as a result of the choice of substrate, explained by the direction of the close packed layers in the film. The authors believe that the ability to deposit epitaxial ferrimagnetic films with angstrom thickness control at low temperatures will make a major impact on the possibility to grow multiferroic stacks and on low temperature monolithic device integration where a spontaneously magnetized sample is required.

• Hansen, Per-Anders Stensby; Granerød, Cecilie Skjold; Prytz, Øystein & Nilsen, Ola (2019). Controlling luminescence and quenching mechanisms in subnanometer multilayer structure of europium titanate thin films. Journal of Luminescence. ISSN 0022-2313. 215. doi: 10.1016/j.jlumin.2019.116618. Full text in Research Archive Show summary

  We have investigated how layered structures of TiO2 and Eu2O3 on the subnanometer scale control the optical absorption, energy transfer, emission and quenching mechanisms in sensitized lanthanide luminescence systems. By using atomic layer deposition (ALD) as a tool for designing materials with sub nanometer precision, we have been able to make structures ranging from separate (TiO6)8- clusters to bulk TiO2, and series of samples showing transitions from 3D to 2D energy migration. Photoluminescence, excitation and decay measurements have been used alongside transmission electron microscopy (TEM) to investigate how the different structures affect the luminescence. We show that it is possible to drastically suppress concentration quenching compared to solid solutions by designing materials as multilayered structures that confines energy migration in 2D planes. This allows for application of higher concentrations of lanthanides and more defected structures, also enabling use of less pure reactants during synthesis.

• Sønsteby, Henrik Hovde; Nilsen, Ola & Fjellvåg, Helmer (2019). Chemical Uniformity in Ferroelectric KxNa1−xNbO3 Thin Films. Global Challenges. 3(10), p. 1800114–1800114. doi: 10.1002/gch2.201800114. Full text in Research Archive Show summary

  Potassium sodium niobate (KNN) has long been considered a viable candidate for replacing lead‐based materials in piezo‐ and ferroelectric devices. The introduction of KNN on an industrial scale is highly awaited; however, processing challenges still remain to be solved. The main obstacle is lack of reproducible growth of uniform boules or thin films at temperatures that facilitate monolithic device integration. Herein, atomic layer deposition (ALD) of KNN thin films, exhibiting high chemical uniformity over large areas, is reported. The cation composition can be controlled at a 1% level, enabling fine‐tuning of the film stoichiometry across the morphotropic phase boundaries of the KNbO3–NaNbO3 solid solution. The films are obtained as highly oriented on Pt (111)||Si (100)‐substrates after annealing at temperatures as low as 550 °C. They exhibit converse piezoelectric effects with magnitudes in accordance with literature. It is believed that the successful development of the described ALD process represents a major step toward achieving lead‐free piezo‐ and ferroelectrics on an industrial scale.

• Momtazi, Leva; Sønsteby, Henrik Hovde & Nilsen, Ola (2019). Biocompatible organic-inorganic hybrid materials based on nucleobases and titanium developed by molecular layer deposition. Beilstein Journal of Nanotechnology. ISSN 2190-4286. 10(1), p. 399–411. doi: 10.3762/bjnano.10.39. Full text in Research Archive Show summary

  We have constructed thin films of organic–inorganic hybrid character by combining titanium tetra-isopropoxide (TTIP) and the nucleobases thymine, uracil or adenine using the molecular layer deposition (MLD) approach. Such materials have potential as bioactive coatings, and the bioactivity of these films is described in our recent work [Momtazi, L.; Dartt, D. A.; Nilsen, O.; Eidet, J. R. J. Biomed. Mater. Res., Part A 2018, 106, 3090–3098. doi:10.1002/jbm.a.36499]. The growth was followed by in situ quartz crystal microbalance (QCM) measurements and all systems exhibited atomic layer deposition (ALD) type of growth. The adenine system has an ALD temperature window between 250 and 300 °C, while an overall reduction in growth rate with increasing temperature was observed for the uracil and thymine systems. The bonding modes of the films have been further characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction, confirming the hybrid nature of the as-deposited films with an amorphous structure where partial inclusion of the TTIP molecule occurs during growth. The films are highly hydrophilic, while the nucleobases do leach in water providing an amorphous structure mainly of TiO2 with reduced density and index of refraction.

• Getz, Michael; Nilsen, Ola & Hansen, Per-Anders Stensby (2019). Sensors for optical thermometry based on luminescence from layered YVO4: Ln3+ (Ln = Nd, Sm, Eu, Dy, Ho, Er, Tm, Yb) thin films made by atomic layer deposition. Scientific Reports. 9(1). doi: 10.1038/s41598-019-46694-8. Full text in Research Archive
• Zhang, Zengxing; Wang, Yonghua; Hansen, Per-Anders Stensby; Du, Kang; Gustavsen, Kim Robert & Liu, Guohua [Show all 10 contributors for this article] (2019). Black silicon with order-disordered structures for enhanced light trapping and photothermic conversion. Nano Energy. ISSN 2211-2855. 65, p. 1–8. doi: 10.1016/j.nanoen.2019.103992. Full text in Research Archive Show summary

  Black silicon has become a versatile substrate for photoelectric and photothermic application due to its excellent light trapping ability. However, subsequent material engineering can conflict with its intrinsic anti-reflective behavior. In this paper, we present a two-step etching approach to create novel black silicon combining ordered micropores and disordered nanopores. The larger pores increase the optical path length and provide space to load functional materials, while the smaller ones facilitate coupling between the incident solar radiation and material. The proposed etching method increases the light-trapping ability of conventional nanostructured black silicon and achieves enhanced absorption in a broad spectrum. Besides, loading Au nanoparticles further improve the light absorbance in the near-infrared range of 1100–1700 nm. The intrinsic SiOx-rich layer on silicon surface produced during SF6/O2 plasma etching leads to photothermic conversion being the dominant dissipation route for the light energy, thereby yielding outstanding performance in photothermic and photo-thermal-electric demonstrations. This work establishes a robust relationship between three-dimensional structure and light-trapping property of black silicon and provides insights into substrate designs that facilitate the light conversion.

• Momtazi, Leva; Dartt, Darlene Ann; Nilsen, Ola & Eidet, Jon Roger (2018). Molecular layer deposition builds biocompatible substrates for epithelial cells. Journal of Biomedical Materials Research. Part A. ISSN 1549-3296. 106(12), p. 3090–3098. doi: 10.1002/jbm.a.36499. Full text in Research Archive

View all works in NVA

• Svenum, Ingeborg-Helene; Dahl, Øystein; Sunding, Martin Fleissner; Killi, Veronica Anne-Line Kathrine; Grandcolas, Mathieu & Andreassen, Magnus [Show all 10 contributors for this article] (2026). Operando insight into Fermi-level (un)pinning at Ta3N5/NiOx/electrolyte interfaces during photoelectrochemical water splitting. Full text in Research Archive
• Skurtveit, Amalie; Berdiell, Izar Capel; Khairnar, Abhishek; Amrheim, Simon; Peters, Simone & Gottlinger, Mara [Show all 9 contributors for this article] (2026). Inorganic Coatings of Sulfide-Based Solid Electrolytes Through Atomic Layer Deposition. Full text in Research Archive Show summary

  Solid-state batteries (SSBs) are regarded as a promising next-generation energy storage technology, offering a safer, more sustainable, and potentially cost-effective alternative compared to conventional Li-ion batteries (LIBs). The key component for high-performing SSBs is the solid-state electrolyte (SSE) with targeted properties (such as electrochemical stability window, performance, and safety). However, introduction of SSE also brings new challenges related to ionic conductivity, processability, recyclability, and the interface between the active material and the SSE that needs to be carefully controlled. These challenges are addressed with the FUNCY-SSB (FUNctional Coatings of sulfide electrolYtes for lithium Solid-State Batteries) project.

• Trautner, Viktoria Elisabeth; Rogowska, Melania; Plümper, Oliver; Nilsen, Ola & Dziadkowiec, Joanna (2026). How hard do crystals push when growing under confinement? Real-time measurements of surface forces during hydration of periclase to brucite. doi: 10.5194/egusphere-egu26-7493. Full text in Research Archive Show summary

  Interactions between minerals and reactive fluids in porous rocks and building materials often result in crystallization of new minerals. The forces exerted by minerals growing under confinement on the surrounding matrix can be large enough to cause fracturing. Fractures expose new reactive surfaces, leading to progressive disintegration of the material. These processes can result in severe damage to cultural heritage and modern infrastructure, as well as changes in the rheological properties and weathering of natural rocks. Understanding and controlling volume-expanding mineral replacement reactions in pore spaces is thus an important objective to address both societal and geological issues. While crystallization pressures have been measured at larger scales, nanoscale force evolution during confined mineral growth remains poorly constrained.Here, we investigate volume-expansive mineral reactions in pores spaces by studying the hydration of MgO (periclase) in the Surface Forces Apparatus (SFA). Hydration of MgO to Mg(OH)­2 (brucite) causes a volume increase to 220%, yielding high crystallization pressures. We use MgO thin films (~90 nm) prepared by atomic layer deposition as reactive surfaces in our experiments, which are performed at the Flow Laboratory, Njord Center, University of Oslo. With the SFA, we measure distance-resolved adhesive and repulsive forces acting between two MgO surfaces under variable external load and how these change over time as the reaction progresses. Preliminary results indicate evolution of forces from strongly adhesive to repulsive during the hydration reaction, likely due to the presence of amorphous, gel-like precursors in the early stages of the reaction. As a reference for the SFA experiments, we study the hydration of isolated MgO surfaces with Atomic Force Microscopy (AFM). This allows us to compare nucleation and growth rates, as well as microstructure and porosity of Mg(OH)­2 grown in SFA and AFM.

• Trautner, Viktoria Elisabeth; Dziadkowiec, Joanna; Rogowska, Melania & Nilsen, Ola (2025). Hydration of MgO under confinement: investigating damaging mineral growth in the Surface Forces Apparatus. Full text in Research Archive Show summary

  Crystallization of new minerals resulting from interactions with reactive fluids is common in porous rocks and building materials. The forces exerted by minerals growing under confinement on the surrounding matrix can be large enough to cause fracturing and disintegration. This can lead to severe damage to cultural heritage and modern infrastructure. Understanding and controlling volume-expanding mineral replacement reactions in pore spaces is thus an important objective. As part of an ongoing research project investigating damaging mineral growth under confinement, we study the hydration reaction of MgO (periclase) in the Surface Forces Apparatus (SFA). Hydration of MgO to Mg(OH)¬2 (brucite) causes a volume expansion of 220%, yielding high crystallization pressures. With the SFA, we can measure the forces acting between two surfaces under variable external load, as well as the distance between the surfaces, and how these evolve over time as the reaction progresses. We seek to use two types of reactive surfaces in our experiments: 1. MgO single crystals polished to ~10 µm thickness, and 2. MgO thin films (~200 nm) on mica prepared by atomic layer deposition. As a reference for the SFA experiments, we study the hydration of isolated MgO surfaces with Atomic Force Microscopy (AFM). This allows us to compare nucleation and growth rates, as well as microstructure and porosity of Mg(OH)¬2 grown in SFA and AFM. All experiments are performed at the Flow Laboratory, Njord Center, University of Oslo.

• Berland, Kristian; Sødahl, Elin Dypvik; Seyedraoufi, Seyedmojtaba; Nilsen, Ola; Görbitz, Carl Henrik & Walker, Julian Bradley [Show all 7 contributors for this article] (2025). Ferroelectric and piezoelectric molecular crystals: From database mining to computational design. Full text in Research Archive
• Choubey, Anjali; Nilsen, Ola; Wenckstern, Holger Von & Sønsteby, Henrik Hovde (2024). Utilizing low-temperature ALD technique to investigate perovskite nickelates for photovoltaic applications. Full text in Research Archive Show summary

  Photovoltaic (PV) materials currently in use like silicon are well-established but approaching their theoretical limit, and halide-perovskites, even though developing rapidly, are toxic and unstable under environmental conditions. Developing new materials for PV applications is slowly becoming a crucial necessity. In this study, perovskite nickelates are investigated as an alternative to traditional PV materials. Nickelates are not only stable under environmental conditions, but they can also withstand photobleaching and thermal exposures. Additionally, they are well known for their metal-insulator phase transition, magnetic phase transition, and structural transition [1, 2]. This has made them very lucrative for various electronic, magnetic, dielectric, superconducting, and catalytic applications. However, there is not much data on the use of nickelates for PV applications, and we are trying to bridge that gap. Some perovskite nickelates have shown bandgap tuning abilities by A-site substitution control [2-4]. In this work, Terbium nickelate (TbNiO3) and Gadolinium nickelate (GdNiO3) thin films fabricated using low-temperature atomic layer deposition (ALD) techniques were studied and characterized. X-ray diffraction gave information about the structure and crystallinity, x-ray fluorescence and x-ray photoelectron spectroscopy about the composition, and spectroscopic ellipsometry about the thickness and refractive indices of the deposited films. These investigations helped gain valuable insight into the extent of the semiconductive nature of these materials and how to exploit them for PV applications. Reference: 1. Catalano, S., et al., Reports on Progress in Physics, 81(4), 046501 (2018). 2. Mercy, A., et al., Nature Communications, 8(1), (2017). 3. Chang, L., et al., Journal of Physics D: Applied Physics, 49(44), (2016). 4. Chang, L., et al., ACS Applied Materials & Interfaces, 11(17), (2019).

• Dinesh, Dharsana Pulikkottil; Valldor, Björn Martin; Nilsen, Ola & Sønsteby, Henrik Hovde (2024). Ozone based Atomic Layer Deposition of Titanium Dioxide (TiO2 ) using TTIP. Full text in Research Archive
• Rogowska, Melania; Hansen, Per-Anders Stensby & Nilsen, Ola (2024). Luminescent lanthanide-organic hybrid materials by atomic/molecular layer deposition. Full text in Research Archive
• Dinesh, Dharsana Pulikkottil; Nilsen, Ola; Valldor, Björn Martin & Sønsteby, Henrik Hovde (2024). Barium Titanate Thin Films with Ozone Assisted ALD: Binary Oxides Deposition. Full text in Research Archive
• Nilsen, Ola (2023). MLD as a Sandbox for Photoactive Hybrid Materials. Full text in Research Archive
• Sannes, Johnny Andreas; Gonano, Bruno; Fjellvåg, Øystein Slagtern; Kumar, Susmit; Nilsen, Ola & Valldor, Björn Martin (2023). X-ray and neutron diffraction studies of SrTe2FeO6Cl, an oxide chloride with rare ordering of anions. Full text in Research Archive
• Dahl, Øystein; Sunding, Martin Fleissner; Thøgersen, Annett; Killi, Veronica Anne-Line Kathrine; Svenum, Ingeborg-Helene & Grandcolas, Mathieu [Show all 10 contributors for this article] (2023). Direct observation of interfacial energetics at Ta3N5/electrolyte and Ta3N5/NiOx/electrolyte heterojunctions by operando ambient pressure X-ray photoelectron spectroscopy during photoelectrochemical water splitting. Full text in Research Archive
• Dahl, Øystein; Sunding, Martin Fleissner; Thøgersen, Annett; Killi, Veronica Anne-Line Kathrine; Svenum, Ingeborg-Helene & Grandcolas, Mathieu [Show all 10 contributors for this article] (2023). Operando observation of interfacial energetics at the Ta3N5/electrolyte heterojunction by ambient pressure X-ray photoelectron spectroscopy for photoelectrochemical water splitting. Full text in Research Archive
• Skare, Marte Orderud; Ulvestad, Asbjørn; Mæhlen, Jan Petter; Nilsen, Ola & Koposov, Alexey (2022). Accelerating the development of new silicon-based anode materials. Full text in Research Archive
• Killi, Veronica Anne-Line Kathrine; Thøgersen, Annett; Cavallo, Carmen; Das, Supti; Koposov, Alexey & Nilsen, Ola (2021). Coating of powder by ALD. Full text in Research Archive
• Fjellvåg, Øystein; Sønsteby, Henrik Hovde; Nilsen, Ola; Wolff, Max; Kapaklis, Vassilios & Fjellvåg, Helmer [Show all 8 contributors for this article] (2020). Towards Multiferroic Thin Film Composites by Atomic Layer Deposition (ALD). Full text in Research Archive
• Kvalvik, Julie Nitsche; Hansen, Per-Anders Stensby & Nilsen, Ola (2019). Area-selective deposition of MoO3 thin films by atomic layer deposition. Full text in Research Archive
• Brennhagen, Anders; Kvamme, Kristian Breivik; Sverdlilje, Katja S. S. & Nilsen, Ola (2019). Amorphous Iron Phosphates for Thin Film batteries. Full text in Research Archive
• Koposov, Alexey; Gandrud, Knut Bjarne; Lai, Samson Yuxiu; Jensen, Ingvild Julie Thue; Nagell, Marius Uv & Nilsen, Ola [Show all 7 contributors for this article] (2019). Silicon on the Road. Full text in Research Archive Show summary

  IFE together with the UiO, University of Tours (France) and SINTEF recently started a new project “Silicon-on-the-Road”, with the primary aim to develop new silicon-based anode materials for lithium ion batteries. Stabilizing the surfaces of silicon particles has proven to be the most challenging step in the development of high capacity silicon-based electrodes. One of the objectives is therefore to create a material that than can coat the active particles and deliver structural integrity for the anode while keeping all the attractive properties of silicon. The project encompasses a range of coating and analyses methodologies. The current presentation will focus on results obtained using one of the more versatile methods; Atomic Layer Deposition (ALD) and our recent results on thin-film electrodes of amorphous Si as model systems for coating development. This project is co-funded by Norwegian industry and the Research Counsil of Norway through the EnergiX program.

• Hval, Halvor Høen; Ruud, Amund; Forseth, Sissel; Emerich, Hermann; Nilsen, Ola & Fjellvåg, Helmer (2019). Operando investigation of batteries. Full text in Research Archive
• Hval, Halvor Høen; Tripathi, Alok Mani; Ruud, Amund; Emerich, Hermann; Forseth, Sissel & Nilsen, Ola [Show all 7 contributors for this article] (2019). Make Batteries Safe Again. Full text in Research Archive
• Hval, Halvor Høen; Tripathi, Alok Mani; Ruud, Amund; Emerich, Hermann; Forseth, Sissel & Nilsen, Ola [Show all 7 contributors for this article] (2019). Make Batteries Safe Again. Full text in Research Archive
• Gorzkowska-Sobas, Agnieszka A; Lausund, Kristian Blindheim; Petrovic, Veljko; Koning, Martijn de; Chavan, Sachin Maruti & Smith, Martin W. [Show all 7 contributors for this article] (2019). Ammonia adsorption in metal-organic framework materials MLD-deposited on functional substrate for respiratory protection purposes. Full text in Research Archive
• Koning, Martijn de; Gorzkowska-Sobas, Agnieszka A; Lausund, Kristian Blindheim; Petrovic, Veljko; Nilsen, Ola & Smith, Martin W. (2019). Thin layers of UiO-66-NH2 and their catalytic activity towards selected chemical warfare agents. Full text in Research Archive
• Chavan, Sachin Maruti; Gorzkowska-Sobas, Agnieszka A; Koning, Martijn de; Lausund, Kristian Blindheim; Petrovic, Veljko & Nilsen, Ola (2019). Towards adsorptive and catalytically active materials using an all-gas-phase UiO-66-NH2 synthesis approach. Full text in Research Archive
• Brennhagen, Anders & Nilsen, Ola (2019). Forskningstorget 2019 - Batteriproduksjon på stand. Full text in Research Archive
• Kvamme, Kristian Breivik; Ruud, Amund; Weibye, Kristian & Nilsen, Ola (2019). Phosphites as precursors in thin film synthesis. Using LiPO as cathode coating in Li-ion batteries. Full text in Research Archive
• Kvamme, Kristian Breivik; Ruud, Amund; Weibye, Kristian & Nilsen, Ola (2019). Phosphites as precursors in thin film synthesis. Using LiPO as cathode coating in Li-ion batteries. Full text in Research Archive
• Dziadkowiec, Joanna; Zareeipolgardani, Bahareh; Bratvold, Jon E.; Nilsen, Ola; Dysthe, Dag Kristian & Røyne, Anja (2019). Long-range repulsive forces between reactive calcite surfaces are generated due to nucleation in a confined solution. Full text in Research Archive
• Skottvoll, Frøydis Sved; Nilsen, Ola; Krauss, Stefan; Sullivan, Gareth & Wilson, Steven Ray Haakon (2018). Integrating highly miniaturized LC-MS systems with “Organ on a Chip”; the future of preclinical modelling. Full text in Research Archive
• Hval, Halvor Høen; Ruud, Amund; Forseth, Sissel; Emerich, Hermann; Nilsen, Ola & Fjellvåg, Helmer (2018). Operando investigation of batteries. Full text in Research Archive
• Hval, Halvor Høen; Ruud, Amund; Forseth, Sissel; Emerich, Hermann; Nilsen, Ola & Fjellvåg, Helmer (2018). Operando investigation of batteries. Full text in Research Archive
• Dziadkowiec, Joanna; Javadi, Shaghayegh; Bratvold, Jon E.; Nilsen, Ola & Røyne, Anja (2018). Adhesive and repulsive forces between calcite surfaces. Full text in Research Archive
• Kvamme, Kristian Breivik; Sverdlilje, Katja Sofie Støren & Nilsen, Ola (2018). Thin film batteries at UiO. Full text in Research Archive Show summary

  Batteries are fast becoming the go-to energy storage solution of our future, even for highly demanding applications such as aviation. The growing expectations and demands for our future batteries require radical improvements in both design and construction. Several approaches are being pursued throughout the research community. At UiO, we are exploring solid-state electrolytes to fulfil these demands. Changing from a liquid to a solid electrolyte is a drastic change in battery design, and solid electrolytes will significantly improve the properties of batteries. This will in turn enable new applications and further decouple our civilization from fossil fuels. Most solid materials have low ionic conductivity, but not all. We are exploring solid materials with high ionic conductivity, including combinations of organic and inorganic structures forming a class of hybrid materials. This work is based on our previous, successful work on high-performance FePO4 cathode materials that show quasi-capacitive behaviour.

• Alstad, Andreas; Nilsen, Ola & Sønsteby, Henrik Hovde (2024). Atomic layer deposition of barium stannate. Universitetet i Oslo. Full text in Research Archive
• Amedjkouh, Yani Leo; Nilsen, Ola & Sønsteby, Henrik Hovde (2024). The Effect of Cobalt Precursors on Cobaltate Thin Films. Universitetet i Oslo. Full text in Research Archive
• Rogowska, Melania & Nilsen, Ola (2023). Antimicrobial surfaces through photoactivation. University of Oslo, Faculty of Mathematics and Natural Sciences, Department of Chemistry. Full text in Research Archive
• Issa, Abdinassir Hassan & Nilsen, Ola (2023). Porous Coatings for Chromatography Enhanced Sensors. Universitetet i Oslo. Full text in Research Archive
• Skottvoll, Frøydis Sved; Wilson, Steven Ray Haakon & Nilsen, Ola (2022). Liver organoids, mass spectrometry, and separation science. Universitetet i Oslo. Full text in Research Archive Show summary

  Organoids are predicted to change the future of medicine by acting as an in vitro 3D representation of human organ functionality. Organoids are grown from patient derived stem cells or adult tissue, which promise to enable new and faster drug discovery, disease modeling and personalized medicine under more realistic conditions. Organoids are still at the developmental stage and fundamental questions concerning the functionality of the developed organoids remain to be answered. Compared to other biosampling techniques, mass spectrometry (MS) has rarely been used in organoid analyses. This thesis leverages MS and separation science to analyze the biological properties of liver organoids, spanning from protein identification to small molecule drug metabolite detection. With the aim of developing selective, high throughput analyses and online biosampling integration, both conventional and cutting edge electromembrane extraction (EME) sample preparation approaches were explored. Using bioanalytical tools including MS and separation science, we could establish that the liver organoids displayed liver organ functionality. The bioanalytical strategies we developed for liver organoid analyses contribute to greater insight into organoid response and functionality and could be important tools in future organoid development. Furthermore, online organoid integration using electromembrane extraction developed here could be used as a starting point towards developing future organ-on-a-chip systems integrated with mass spectrometry, which would be valuable in drug development, disease modeling, and personalized medicine.

• North, Erlend Tiberg; Nilsen, Ola & Hansen, Per-Anders Stensby (2022). Quinizarin as Organic Sensitizer in LnF3 Thin Films for Photon Upconversion. Universitetet i Oslo. Full text in Research Archive Show summary

  This thesis illuminates the opportunities for Quinizarin (Qz) as an organic sensitizer in LnF3 (Ln=Y, Nd, Tm, Yb) thin films for upconversion. Lanthanides show great promise as active materials for upconversion technologies, but struggle with very low absorption and thus, very low efficiency. We attempt to correct this by including a broad band absorber, in our case an organic dye. Atomic layer deposition (ALD) has been used to build the multilayered structures with control of the interatomic separations. The project has been divided into multiple parts, focusing first on Qz as sensitizer and its properties in solid state by ALD growth of Ln2Qz3. The ALD growth of LnF3 thin films was investigated and multilayered structures intended to show upconversion was made. Initial investigations of Qz show that as a dispersed molecule, its luminescence is heavily influenced by its environment, but indicates it could function as a sensitizer. When combined with Ln(thd)3 as a precursor in ALD growth, it shows exceptionally good growth with high growth rate, as well as high optical absorption. The growth and structure of LnF3 thin films using NH4F as fluorine source has been characterized using quartz crystal microbalance (QCM), with results indicating similar type of growth among all the tested lanthanides, apart for Nd, which proved more challenging. Uniform film with growth rates of around 0.6 Å/cycle were achieved, and NH4F has been proven a good fluorine source in LnF3 systems using Ln(thd)3. Qz has been successfully incorporated into these films with high absorption for high Qz-content, as characterized by using ultraviolet, visible and near infrared spectroscopy (UV-Vis). However, the films were not luminescent, as aimed for, proving that there is more work to be done to understand the quenching mechanisms involved. The upconversion structure itself has been investigated by growing and investigating multilayers of YbF3 with Nd3+ and Tm3+. Using cathodoluminescence (CL) both ions have been shown incorporated in the structure. The system shows different emission intensities depending on ion distance, with 0.8 nm being the most optimal for CL signal.

• Tran, Martin; Nilsen, Ola; Rogows, Melania; Hansen, Per-Anders Stensby & Valen, Håkon (2021). Photodynamic inactivation of bacteria with ZrTCPP thin films. Universitetet i Oslo. Full text in Research Archive
• Kvalvik, Julie Nitsche; Nilsen, Ola & Hansen, Per-Anders Stensby (2021). Design and deposition of CaMoO4 as host for solar down-converters. Universitetet i Oslo. Full text in Research Archive Show summary

  Silicon solar cells are approaching their maximum theoretical efficiency, but can still be improved by adapting the solar light to match the solar cell. Trough down-conversion, the energy that is above the absorption edge for silicon can be converted to more suitable energy packets. Down-conversion systems usually consist of a lanthanide pair embedded in a host material. However, efficient down-converters are difficult to synthesize, as the distance between the lanthanides must be controlled on a nanometer scale and a too high concentration of lanthanides will reduce efficiency. In the current work, CaMoO4 thin films doped with Pr3+ and Yb3+ are made using atomic layer deposition (ALD), which allows control of both position and amount of lanthanides. In order to deposit such complex oxides with ALD, the processes for the binary oxides are combined. There was no compatible process for deposition of MoOx when this work started, and the one developed was in fact area-selective. The work has also shown how design of experiments, can be used to develop ALD processes faster. Lastly, we found that the optical properties of CaMoO4:Pr3+, Yb3+ could be controlled by tuning the ALD process.

• Sørensen, Silje Holm; Nilsen, Ola & Hansen, Per-Anders Stensby (2020). Organic Sensitization in Lanthanide Fluoride Nanostructures for Upconversion. Universitetet i Oslo. Full text in Research Archive
• Killi, Veronica Anne-Line Kathrine; Nilsen, Ola & Sønsteby, Henrik Hovde (2020). Tynne filmer av ruthenater med atomlagsdeposisjon (ALD). Universitetet i Oslo. Full text in Research Archive Show summary

  Rutheniumoksider har stort potensial innen utvikling av fremtidens teknologi, spesielt SrRuO3. SrRuO3 er et sjeldent tilfelle av et ferromagnetisk innskuddsmetalloksid, og kan føre til store teknologiske fremskritt innen oksidbasert elektronikk. Det er et veldig ettertraktet elektrodemateriale på grunn av høy stabilitet, god elektrisk ledningsevne og at det hindrer polarisasjonsutmattelse i ferroelektriske komponenter. SrRuO3 kan også brukes i magnetiske tunneleringsoverganger, som i magnetoresisiv random access memory (MRAM). Ruthenater er kjent for å ha magnetiske og elektriske egenskaper som er sterkt koblet til struktur, og derfor er tynne filmer av særdeles stor interesse. Tynne filmer gir muligheten til å kontrollere utformingen av materialer og gi spesifikke stressinduserte deformasjoner som fremmer funksjonelle egenskaper. Mange teknikker for å fremstille tynne filmer av SrRuO3 møter utfordringer med høy deposisjonstemperatur som fører til strukturelle og støkiometriske avvik i SrRuO3 og lagdelte strukturer. Disse utfordringene kan man overkomme ved bruk av atomlagsdeposisjon (ALD), en teknikk som er kjent for lav deposisjonstemperatur. I dette prosjektet er SrRuO3, og de relaterte materialene CaRuO3 og LaRuO3, forsøkt deponert med ALD av β-diketonater og forskjellige oksygenkilder. Det er ikke publisert arbeid på disse ternære oksidene med ALD tidligere. Vekstoppførsel og rutheniuminnhold er grundig undersøkt med ellipsometri, EDS og QCM. Binært ruteniumoksid ble fremstilt for Ru(thd)3 og oksygengass, men ikke med Ru(thd)3 og ozon. Sr-Ru-O-systemet fikk veldig begrenset vekst av film for Ru(thd)3 og Sr(thd)2∙H2O med vann og ozon i kombinasjon som oksygenkilde. Ca-Ru-O-systemet med ozon hadde høyere GPC enn forventet av sykluser med Ca(thd)2 og ozon alene, men marginalt rutheniuminnhold. Tidligere arbeid med strontium- og kalsiumforløpere viser at de reagerer kraftig med sine omgivelser og er umulige å stabilisere i binære oksider uten forurensninger. De dannet ikke stabile ternære oksider med Ru(thd)3 i dette prosjektet. La-Ru-O-systemet førte til rutheniumholdige filmer av La(thd)3 og Ru(thd)3 med oksygenkildene ozon og oksygengass, men en øvre grense for rutheniuminnhold på 40 atomprosent av relativt kationinnhold. Flere lantanforløpere har vellykket fremstilt lantanoksid og flere ternære oksider, og bidro trolig for å oppnå økt stabilitet i et ternært system med Ru(thd)3. Denne stabiliseringen bidro til tynne filmer med betydelig rutheniuminnhold på tross av observert ozonetsning av rutheniumforløperen. QCM-analyse av La-Ru-O-systemet viste stor påvirkning av temperatureffekter ved pulsing av oksygenforløperne, og rutheniumforløperen viste ikke-intuitiv masseøkning med oksygengass og stort massetap med ozon. XRD-undersøkelse tyder på tap av rutheniuminnhold ved varmebehandling etter endt deposisjon sammenlignet med det målte rutheniuminnholdet før varmebehandlingen med EDS. LaFeO3 og SrFeO3 er beslektede systemer til LaRuO3 og SrRuO3, og er inkludert i denne studien. Det finnes allerede stabile ALD-prosesser av LaFeO3 og SrFeO3 med β-diketonater og ozon. Det viser at lantan og strontium danner stabile systemer med jern i et ternært oksid. Ruthenium ligger en periode under jern i periodesystemet, men reagerer med ozon og gir kompleks vekstoppførsel med oksygengass. Disse systemene har forskjellige kjemiske egenskaper og lantan spiller en viktig rolle for å stabilisere ruthenium i et ternært system. La-Fe-O-systemet viste en tydelig sammenheng mellom antall kationsykluser og kationinnhold, og førte til krystallinske, epitaksielle filmer av LaFeO3 på LaAlO3- og SrTiO3-substrater. SrFeO3 beviser at SrO kan bli stabilisert i et ternært oksid. Vekstoppførsel, og hvordan endring i eksperimentelle parametere påvirket vekstoppførsel, ble undersøkt for Sr-Fe-O-systemet i dette prosjektet. Denne avhandlingen gir et innblikk i hvordan komplekse oksider har et mangfold av egenskaper, men by på utfordrende kjemi i forsøket på å fremstille dem.

• Li, Xinyu; Fjellvåg, Helmer & Nilsen, Ola (2020). Na-Based Layered Tellurate Na2M2TeO6 (M = Zn, Mg): Synthesis, Crystal Structure and Na+ Ion Diffusion. Universitetet i Oslo. Full text in Research Archive
• Petrovic, Veljko; Nilsen, Ola & Lausund, Kristian Blindheim (2019). Boronic acids in Molecular Layer Deposition. Universitetet i Oslo. Full text in Research Archive
• Brennhagen, Anders; Nilsen, Ola; Kvamme, Kristian Breivik & Sverdlilje, Katja S. S. (2019). Synthesis and electrochemical characterization of thin film iron phosphates as cathode material for Li-ion batteries. Universitetet i Oslo. Full text in Research Archive Show summary

  Solid-state batteries is one of the main contenders for domination of the future battery marked. Thin film technology is important in the development of these batteries. In this work, we have shown that amorphous thin film FePO4 with a thickness around 10 nm, deposited by atomic layer deposition (ALD), can reach a specific power above 1 MW/kg and approach theoretical capacity at lower currents. The 10 nm thin film also shows very good cycling stability at elevated currents and can retain 70 % of peak capacity after 8000 cycles at 80 µA (40C). The material also shows a significant self-enhancing mechanism leading to an increase in capacity during early cycling stages. We observed a capacity increase of 90 % for 10 nm after 100 cycles at 80 µA. In this study, we used quartz crystal microbalance (QCM) analysis to establish a stable ALD process for depositing amorphous thin films from the Fe-P-O system. By varying the pulsing ratio between the precursors, we obtained films with different compositions and chose to study Fe4(P2O7)3 and FePO4 more in detail. The films were uniform and flat with an RMS roughness below 1 nm. As the FePO4 films proved to be significantly better than the Fe4(P2O7)3, we focused mainly on FePO4. We used galvanostatic cycling (GC), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) to characterize the electrochemical properties of the thin films. An important part of this study was to develop a good baseline for testing, including the use of reference batteries. In this work, we confirmed that LiClO4 is a better choice than LiPF6 as electrolyte for testing thin film cathodes, because of minimal side reactions with the steel casing. The FePO4 thin films show a combination of capacitive and redox behavior where both contribute to the capacity. In this study, we have tried to separate the two contributions and find their thickness and current dependency. In an attempt to increase the area capacity of the cathodes without increasing the film thickness, we created soot substrates with high surface 3D structures of carbon, deposited from the flames of a candle. We managed to maintain the structure and evenly coat it with FePO4. Despite the increase in mass, we obtained no higher capacity or better battery performance from the soot batteries.

• Olsen, Malin Solheim; Nilsen, Ola & Rukke, Håkon Valen (2019). Porphyrin-based films for photodynamic inactivation of bacteria. Universitetet i Oslo. Full text in Research Archive
• Bratvold, Jon E.; Nilsen, Ola & Fjellvåg, Helmer (2019). Towards a Model System for Lamellar Magnetism by Atomic Layer Deposition. Universitetet i Oslo. Full text in Research Archive Show summary

  We have developed the first atomic layer deposition (ALD) processes for thin films of iron in a +2 oxidation state (Fe2+), as well as nickel titanate (NiTiO3). These materials are important for the understanding and realization of exotic magnetic properties useful in computer technology. Pushing modern computer technology forward requires insight into more complex materials than bar magnets. With a constant drive towards making devices smaller, producing components in the form of thin films is often the solutions. However, before utilizing desirable properties, they must be understood in order to make the required materials in a controlled manner. An example of materials with interesting magnetic properties are naturally formed rocks from Modum, Norway. They consist of two different minerals, namely hematite (Fe2O3) and ilmenite (FeTiO3). These compounds are quite uninteresting separately, but show fascinating and sought-after magnetic properties when combined. These unique features arise from super-thin alternating layers, with thicknesses down to 1 nanometer. ALD is a technique for making ultra-thin films, much like the layers in the rocks from Modum. The problem is making FeTiO3, which contains iron (Fe) in a +2 oxidation state. Iron is easily oxidized to +3, which is the oxidation state it has in Fe2O3. We have developed the first ALD process to directly deposit thin films with only Fe2+. We then used this process to make FeTiO3. However, the films also contained unwanted substances, and could not be used in combination with Fe2O3. To learn more about the properties of the Modum rocks, another approach was chosen: swapping iron for nickel (Ni), as nickel is easier to keep in oxidation state +2 than iron. This was used in combination with Fe2O3 to create thin, alternating layers with NiTiO3, just as in the rocks from Modum. The magnetic properties of the samples were investigated, and though some interesting features were observed, a full understanding of their origin remains a mystery.

• Momtazi, Leva; Nilsen, Ola & Eidet, Jon Roger (2018). Design and Growth of Bioactive Materials by Molecular Layer Deposition. Universitetet i Oslo. Full text in Research Archive

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