Henrik Hovde Sønsteby

• 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.

• Hessevik, Julie; Sønsteby, Henrik Hovde; Fjellvåg, Helmer & Sjåstad, Anja Olafsen (2025). Reactivity of gaseous PtO2 and RhO2 with LaNiO3 thin films: a systematic XPS study. Materials Advances. 6(3), p. 1097–1106. doi: 10.1039/D4MA00974F. Full text in Research Archive Show summary

  The reaction between volatile platinum and rhodium gas species and bulk materials (alloys or oxides) is of high practical importance in the chemical process industry. Herein, an X-ray photoelectron spectroscopy (XPS) study has been conducted to understand how PtO2(g) and RhO2(g) react with LaNiO3 (LNO) thin films grown via atomic layer deposition (ALD) at elevated temperatures (900 °C). In this study, XPS data for reference powders of La2NiPtO6, LaNi0.95Pt0.05O3, LaNi0.88Rh0.12O3 and LaRhO3 provide a library for the interpretation of oxidation states of platinum and rhodium after reaction with LNO thin films. Upon short exposure to PtO2(g) and RhO2(g), platinum appear as Pt(III) in the LNO surface, but after prolonged exposure, Pt(IV) appears. Complementary diffraction analysis shows that LaNi1−xMxO3 solid solution forms initially where Ni, Pt and Rh are predominantly +III, however, quickly accompanied by the formation of a La2Ni2−2xM2xO6 (M = Pt, Rh) double perovskite phase with its characteristic (004) peak. Rhodium appears as Rh(III) and Rh(IV) in both the R[3 with combining macron]c and the double perovskite like phases. Furthermore, platinum and rhodium depth profiles were generated by the combination of XPS and Ar+ sputtering. Platinum depth profiles reveal major differences between as-grown ALD films and post-annealed films when exposed to PtO2(g). Pt penetrates faster into the LNO material for films without post annealing, probably due to its smaller grain size and larger surface area and grain boundaries. When exposed to a mixture of PtO2(g) and RhO2(g), the Rh : Pt ratio in LNO increases upon prolonged reaction time. These results may have implications on the use of LNO as platinum and rhodium capture material in the Ostwald process.

• 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.

• 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.

• 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.

• 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
• Sønsteby, Henrik Hovde; Yanguas-Gil, Angel & Elam, Jeffrey W. (2020). Consistency and reproducibility in atomic layer deposition. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. ISSN 0734-2101. 38. doi: 10.1116/1.5140603. Full text in Research Archive Show summary

  Atomic layer deposition (ALD) is a thin film synthesis technique that can provide exquisite accuracy and precision in film thickness and composition even on complex, large area substrates. Based on self-limiting surface chemistry, ALD can be insensitive to process conditions and reactor designs, allowing an ALD process developed in one lab to be easily reproduced in other labs. In practice, however, ALD is sometimes difficult to reproduce or replicate, and the results can vary substantially between ALD reactors and between labs. This is exemplified by large deviations in reports on the growth of, e.g., Al2O3, FeOx, and TiO2 given the same precursors under similar conditions. Furthermore, the problem of irreproducibility seems to be growing as ALD is adopted by more researchers and integrated into new applications. In this article, the authors highlight some of the major sources of variations and errors and common misconceptions related to ALD. In particular, the authors focus on issues related to precursors, substrates, and deposition tools. The authors illustrate these problems through examples from the literature, and they present results from numerical simulations that describe how nonidealities would manifest in thickness profiles in a typical cross-flow reactor. They also describe how reproducibility in ALD is linked to consistent experimental practice and reporting between labs. The authors’ hope is that by educating newcomers to ALD and advocating for consistent reporting of deposition conditions, they can minimize irreproducibility and enable ALD practitioners to realize the full potential afforded by self-limiting surface chemistry.

• 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.

• 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.; 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.

• 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.

• Bickford, Justin R; Sønsteby, Henrik Hovde; Strnad, Nicholas A; Zavalij, Peter Y & Hoffman, Robert C (2019). Control of potassium tantalate niobate thin film crystal phase and orientation by atomic layer deposition. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. ISSN 0734-2101. 37(2), p. 020904-1–020904-6. doi: 10.1116/1.5063925. Full text in Research Archive Show summary

  Due to its appreciable electro-optical properties, potassium tantalate niobate (KTN) thin films of high quality are expected to enhance the functionality of integrated photonics optical modulators. Unfortunately, they are inherently hard to synthesize. Herein, the authors present atomic layer deposition (ALD) of oriented KTN for the first time. They study the variability in phase content with respect to potassium concentration across a variety of substrates. Films grown with a slight overstoichiometry in potassium show excellent crystal quality of a pure perovskite phase. Highly oriented films were obtained on substrates of a similar lattice constant to bulk potassium tantalate niobate. Nearly stoichiometric potassium contents yield films with similar quality, albeit with trace amounts of pyrochlore. Potassium deficient films consist of an overwhelming amount of pyrochlore. Phase control and orientation control are essential when considering device integration of optical modulators. The authors believe that ALD is an ideal technique to obtain KTN thin films with high growth control.

• 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.

• Sønsteby, Henrik Hovde; Wind, Julia; Jensen, Martin; Storaas, Thomas Aarflot; Chernyshov, Dmitry & Fjellvåg, Helmer (2019). In situ synchrotron X-ray diffraction of thin films under perturbation by an electric field. Ferroelectrics (Print). ISSN 0015-0193. 537, p. 20–26. doi: 10.1080/00150193.2018.1528953. Full text in Research Archive
• Sønsteby, Henrik Hovde; Aarholt, Thomas; Prytz, Øystein; Fjellvåg, Helmer & Nilsen, Ola (2018). First Complex Oxide Superconductor by Atomic Layer Deposition. Chemical Communications. ISSN 1359-7345. 54(59), p. 8253–8256. doi: 10.1039/c8cc04998j. Full text in Research Archive
• Sønsteby, Henrik Hovde; Bratvold, Jon E.; Weibye, Kristian; Fjellvåg, Helmer & Nilsen, Ola (2018). Phase Control in Thin Films of Layered Cuprates. Chemistry of Materials. ISSN 0897-4756. 30(3), p. 1095–1101. doi: 10.1021/acs.chemmater.7b05005. Full text in Research Archive
• Momtazi, Leva; Sønsteby, Henrik Hovde; Dartt, DA; Eidet, Jon Roger & Nilsen, Ola (2017). Bioactive titaminates from molecular layer deposition. RSC Advances. 7(34), p. 20900–20907. doi: 10.1039/C7RA01918A. Full text in Research Archive Show summary

  Organic–inorganic hybrid materials are an emerging class of materials suitable for deposition by the molecular layer deposition (MLD) technique. Their toolbox is now expanded to include linkers of amino acids, which when combined with titanium form materials that can be termed titaminates, based on the amine and carboxylates present in the amino acids being used as linkers. This is a class of compounds with high potential as bioactive materials, containing essential amino acids and biocompatible titanium. The films have been prepared by combining titanium tetra-isopropoxide (TTIP) with glycine and L-aspartic acid. L-Arginine has also been used, however, without success. Hybrid films of TTIP and succinic acid were also investigated as a comparison to L-aspartic acid due to their structural similarities. All systems show self-limiting growth with a reduction in the growth rate with increasing temperature. The as-deposited films are amorphous, have low surface roughness, exhibit a hydrophilic nature as measured by a goniometer, and bear indications of some porosity towards water. Films based on glycine and L-aspartic acid have been used as substrates for growth of epithelial cells (rat goblet cells) where their proliferation has been monitored. The cell proliferation was significantly increased on these substrates compared to uncoated coverslips.

• Sønsteby, Henrik Hovde; Fjellvåg, Helmer & Nilsen, Ola (2017). Functional perovskites by atomic layer deposition - an overview. Advanced Materials Interfaces. 4:1600903, p. 1–15. doi: 10.1002/admi.201600903. Full text in Research Archive
• Sønsteby, Henrik Hovde; Weibye, Kristian; Bratvold, Jon E. & Nilsen, Ola (2017). Rubidium containing thin films by atomic layer deposition. Dalton Transactions. ISSN 1477-9226. 46(46), p. 16139–16144. doi: 10.1039/c7dt03753h. Full text in Research Archive
• Sønsteby, Henrik; Nilsen, Ola & Fjellvåg, Helmer (2016). Atomic layer deposition of (K,Na)(Nb,Ta)O3 thin films. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. ISSN 0734-2101. 34(4). doi: 10.1116/1.4953406. Full text in Research Archive Show summary

  Thin films of complex alkali oxides are frequently investigated due to the large range of electric effects that are found in this class of materials. Their piezo- and ferroelectric properties also place them as sustainable lead free alternatives in optoelectronic devices. Fully gas-based routes for deposition of such compounds are required for integration into microelectronic devices that need conformal thin films with high control of thickness- and composition. The authors here present a route for deposition of materials in the (K,Na)(Nb,Ta)O3-system, including the four end members NaNbO3, KNbO3, NaTaO3, and KTaO3, using atomic layer deposition with emphasis on control of stoichiometry in such mixed quaternary and quinary compunds.

• Østreng, Erik; Sønsteby, Henrik; Øien, Sigurd; Nilsen, Ola & Fjellvåg, Helmer (2014). Atomic layer deposition of sodium and potassium oxides: Evaluation of precursors and deposition of thin films. Dalton Transactions. ISSN 1477-9226. 43(44), p. 16666–16672. doi: 10.1039/c4dt01930j. Full text in Research Archive Show summary

  Thin films of sodium and potassium oxides have for the first time been deposited using atomic layer deposition. Sodium and potassium complexes of tert-butanol, trimethylsilanol and hexamethyldisilazide have been evaluated as precursors by characterising their thermal properties as well as tested in applications for thin film depositions. Out of these, sodium and potassium tert-butoxide and sodium trimethylsilanolate and hexamethyldisilazide were further tested as precursors together with the Al(CH3)3 + H2O/O3 process to form aluminates and together with ozone to form silicates. Sodium and potassium tert-butoxide and sodium trimethylsilanolate showed self-limiting growth and proved useable at deposition temperatures from 225 to 375 or 300 °C, respectively. The crystal structures of NaOtBu and KOtBu were determined by single crystal diffraction revealing hexamer- and tetramer structures, respectively. The current work demonstrates the suitability of the ALD technique to deposit thin films containing alkaline elements even at 8′′ wafer scale.

• Sønsteby, Henrik; Østreng, Erik; Fjellvåg, Helmer & Nilsen, Ola (2014). Deposition and x-ray characterization of epitaxial thin films of LaAlO3. Thin Solid Films. ISSN 0040-6090. 550, p. 90–94. doi: 10.1016/j.tsf.2013.10.139. Full text in Research Archive
• Sønsteby, Henrik; Østreng, Erik; Fjellvåg, Helmer & Nilsen, Ola (2014). Atomic layer deposition of LaPO4 and Ca:LaPO4. Chemical Vapor Deposition. ISSN 0948-1907. 20(7-9), p. 269–273. doi: 10.1002/cvde.201407112. Full text in Research Archive
• Sønsteby, Henrik; Chernyshov, Dmitry; Getz, Michael; Nilsen, Ola & Fjellvåg, Helmer (2013). On the application of a single-crystal kappa-diffractometer and a CCD area detector for studies of thin films. Journal of Synchrotron Radiation. ISSN 0909-0495. 20, p. 644–647. doi: 10.1107/S0909049513009102. Full text in Research Archive
• Østreng, Erik; Sønsteby, Henrik; Sajavaara, Timo; Nilsen, Ola & Fjellvåg, Helmer (2013). Atomic layer deposition of ferroelectric LiNbO3. Journal of Materials Chemistry C. ISSN 2050-7526. 1(27), p. 4283–4290. doi: 10.1039/c3tc30271g. Full text in Research Archive Show summary

  The ferroelectric and electro-optical properties of LiNbO3 make it an important material for current and future applications. It has also been suggested as a possible lead-free replacement for present PZT-devices. The atomic layer deposition (ALD) technique offers controlled deposition of films at an industrial scale and thus becomes an interesting tool for growth of LiNbO3. We here report on ALD deposition of LiNbO3 using lithium silylamide and niobium ethoxide as precursors, thereby providing good control of cation stoichiometry and films with low impurity levels of silicon. The deposited films are shown to be ferroelectric and their crystalline orientations can be guided by the choice of substrate. The films are polycrystalline on Si (100) as well as epitaxially oriented on substrates of Al2O3 (012), Al2O3 (001), and LaAlO3 (012). The coercive field of samples deposited on Si (100) was found to be ∼220 kV cm−1, with a remanent polarization of ∼0.4 μC cm−2. Deposition of lithium containing materials is traditionally challenging by ALD, and critical issues with such deposition are discussed.

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• Rogowska, Melania & Sønsteby, Henrik Hovde (2026). Atomic layer deposition of BaSnO₃ using novel metal-organic precursors: towards FeFET and FTJ integration. 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
• Sønsteby, Henrik Hovde (2024). Complex Materials for Next Generation Electronics and Photonics - ALD will Prevail! Full text in Research Archive
• Sønsteby, Henrik Hovde (2024). AI feasts on the Power Grid - How to Cope by Developing New Materials Technology. Full text in Research Archive
• Alstad, Andreas & Sønsteby, Henrik Hovde (2024). Novel Synthesis Route for Atomic Layer Deposition of BaSnO3 Thin Films. 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
• Rogowska, Melania; Rykkje, Linn & Sønsteby, Henrik Hovde (2023). Tailoring Lattice Match by Cation Substitution in a Functional Ternary Oxide. Full text in Research Archive
• Sønsteby, Henrik Hovde (2022). Enhanced Cation Control in ALD of Alkali Metal Containing Films by Avoiding Water-Reservoir Effects. Full text in Research Archive
• Sønsteby, Henrik Hovde (2020). Enabling Low-Temperature Epitaxy of Functional Complex Oxides. Full text in Research Archive
• Sønsteby, Henrik Hovde (2020). As Deposited Epitaxial Functional Complex Oxides - Enabling Novel Technology. 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
• Sønsteby, Henrik Hovde (2019). As Deposited Epitaxial LaNiO3 and La(Ni,Cu)O3 with Controllable Electric Properties. Full text in Research Archive
• Sønsteby, Henrik Hovde (2019). Epitaxial Nickelates - On the Path to Oxide Electronics. Full text in Research Archive
• Sønsteby, Henrik Hovde (2019). Atomic Layer Deposition of Functional Oxides - A Neccessary Challenge. Full text in Research Archive
• Sønsteby, Henrik Hovde (2018). Designing High-Performance Composite Multiferroics by ALD. Full text in Research Archive
• Sønsteby, Henrik Hovde (2017). In situ Synchrotron Diffraction During Ferroelectric Switching of Thin Films. Full text in Research Archive
• Nilsen, Ola & Sønsteby, Henrik (2016). ALD - From Ideal to Real. Full text in Research Archive
• Sønsteby, Henrik Hovde (2016). Atomic Layer Deposition of KxNa1-xNbO3. Full text in Research Archive
• Sønsteby, Henrik; Fjellvåg, Helmer & Nilsen, Ola (2015). Deposition of the Important Lead Free Ferroelectric KxNa(1-x)NbO3. Full text in Research Archive
• Sønsteby, Henrik; Nilsen, Ola & Fjellvåg, Helmer (2014). Deposition of the Important Lead Free Ferroelectric KxNa(1-x)NbO3. Full text in Research Archive
• Fjellvåg, Øystein Slagtern; Ruud, Amund; Sønsteby, Henrik; Fjellvåg, Helmer & Nilsen, Ola (2014). Crystallization and electrochemical investigation of α- and β-MoO3 thin films deposited by Atomic Layer Deposition. Full text in Research Archive
• Sønsteby, Henrik; Østreng, Erik; Fjellvåg, Øystein Slagtern; Nilsen, Ola & Fjellvåg, Helmer (2014). Sodium- and Potassium Containing Thin Films by Atomic Layer Deposition. Full text in Research Archive
• Muri, Marte Eiterstraum; Weibye, Kristian; Klepper, Karina Barnholt; Sønsteby, Henrik; Eidet, Jon Roger & Fjellvåg, Helmer [Show all 7 contributors for this article] (2014). Amino acids in organic-inorganic hybrid thin films for biocompatible materials. Full text in Research Archive
• Hu, Yang; Miikkulainen, Ville; Ruud, Amund; Sønsteby, Henrik; Norby, Truls & Nilsen, Ola [Show all 7 contributors for this article] (2013). Electrochemical characterization on ALD-deposited LaPO4 and LiAlO2 thin films. Full text in Research Archive
• Sønsteby, Henrik; Østreng, Erik; Nilsen, Ola & Fjellvåg, Helmer (2012). Deposition and X-ray Characterization of Epitaxial Thin Films of LaAlO3. Full text in Research Archive
• Sønsteby, Henrik; Getz, Michael; Chernyshov, Dmitry; Nilsen, Ola & Fjellvåg, Helmer (2012). Untangling Diffraction Contributions from Epitaxial Thin Films Becomes Easy – Results from Recent Experiments at SNBL. Full text in Research Archive
• Østreng, Erik; Sønsteby, Henrik; Nilsen, Ola & Fjellvåg, Helmer (2012). Crystallization of thin films of LaAlO3 grown by Atomic Layer Deposition. Full text in Research Archive
• Sønsteby, Henrik; Nilsen, Ola & Fjellvåg, Helmer (2012). Growth and Structural Characterization of Atomic Layer Deposited LaAlO3 Thin Films (Including the Exotic LAO||STO Interface). Full text in Research Archive
• Sønsteby, Henrik; Østreng, Erik; Fjellvåg, Helmer & Nilsen, Ola (2010). Growth of the Proton Conductor Ca:LaPO4 by ALD for high temperature fuel cell applications. Full text in Research Archive
• 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
• 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.

• Skaar, Erik; Fjellvåg, Helmer & Sønsteby, Henrik Hovde (2019). Structure-Property Relations in Thin Films of LaNiO3 and LaNi1-xCuxO3. Universitetet i Oslo. Full text in Research Archive
• Sønsteby, Henrik; Fjellvåg, Helmer & Nilsen, Ola (2017). Piezo- and Ferroelectric A+B5+O3 Thin Films. Universitetet i Oslo. Full text in Research Archive Show summary

  This thesis summarizes atomic layer deposition (ALD) of thin films of a set of alkali metal niobates and tantalates with technologically important physical properties. ALD of LiNbO3 is presented first, where we showcase the possibility of epitaxial integration of complex oxide thin films containing alkali metals. LiNbO3 is a high performance ferroelectric, and these properties are studied to show that ALD can be utilized to obtain highly oriented films with piezo- and ferroelectric activity. The thesis continues with investigating the feasibility of growing sodium- and potassium containing materials with ALD. Prior to the work leading to this thesis, no reports of Na/K-deposition by ALD have been available. Several precursors are screened for self-limiting growth under typical ALD-conditions, and two optimal precursors are used to carry out deposition of sodium- and potassium aluminate. These precursors, both alkali metal t-butoxides, offer the possibility to grow sodium- and potassium containing materials, with water as the co-reactant, at temperatures between 250 and 300 °C. Using the results from general deposition of Na/K-containing materials and the experience from LiNbO3- deposition, four alkali metal niobates and tantalates; NaNbO3, NaTaO3, KNbO3 and KTaO3, were deposited. These materials have interesting intrinsic properties, such as ferroelectricity (KNbO3) and photocatalytic activity (NaNbO3). More technologically interesting, however, are the solid solutions KxNa1-xNbO3 and KTaxNb1-xO3, which are desirable for their strong ferroelectric and electrooptical responses, respectively. Proof-of-concept on the intermixing of these solid solutions by ALD is presented, displaying remarkable compositional control and reproducibility. KxNa1-xNbO3 thin films are deposited for investigation of its electric properties, and piezoelectric activity is studied using piezoelectric force microscopy. The films are epitaxially integrated on a range of substrates, thereby controlling the orientation and direction of the polarity. Finally, some general notes on atomic layer deposition of alkali metal containing complex oxides are made, in light of what has been achieved in this work. Three main papers form the basis for this thesis. One on deposition of LiNbO3, a second on Na/Kdeposition and a third on alkali metal niobate/tantalate-deposition.

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