Augustinas Galeckas

• Vijayan, Athira; Andronic, Luminita; Rangasamy, Selvapriya; Galeckas, Augustinas; Abdikamalova, Dinara & Mayandi, Jeyanthinath [Vis alle 7 forfattere av denne artikkelen] (2026). Influence of silicon-modified TiO<inf>2</inf>nanocomposites on the photocatalytic degradation of methyl orange and imidacloprid. Zeitschrift für Physikalische Chemie. ISSN 0942-9352. doi: 10.1515/zpch-2025-0120. Fulltekst i vitenarkiv
• Vijayan, Athira; Andronic, Luminita; Rangasamy, Selvapriya; Galeckas, Augustinas; Abdikamalova, Dinara & Mayandi, Jeyanthinath [Vis alle 7 forfattere av denne artikkelen] (2026). Influence of silicon-modified TiO2 nanocomposites on the photocatalytic degradation of methyl orange and imidacloprid. Zeitschrift für Physikalische Chemie. ISSN 0942-9352. doi: 10.1515/zpch-2025-0120. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Titanium dioxide (TiO 2 ) and its composites are widely investigated for environmental remediation due to their favorable physicochemical properties. In this study, Si/TiO 2 nanocomposites were synthesized by incorporating a very low amount (0.1 wt%) of silicon nanoparticles prepared via a free-space reactor (FSR) into a TiO 2 matrix using a sol–gel method. Three types of silicon nanoparticles with distinct intrinsic properties, denoted as Si(1), Si(2), and Si(3), were employed to systematically evaluate the influence of silicon structure on photocatalytic performance under identical synthesis conditions. The photocatalytic activity of the nanocomposites and pristine TiO 2 was assessed using two reference pollutant molecules widely reported in the literature, methyl orange as a model dye and imidacloprid as a representative persistent organic contaminant, under UV, UV + visible, and visible-light irradiation using low-energy light sources. Among the investigated samples, Si(1)/TiO 2 exhibited the highest photocatalytic efficiency, achieving degradation rates of 94 % for methyl orange (UV irradiation, 240 min) and 60 % for imidacloprid (UV irradiation, 360 min), outperforming pristine TiO 2 (76 % and 53 %, respectively). The enhanced performance is attributed to improved interfacial charge transfer, optimized textural properties, and extended light absorption induced by silicon incorporation. The research demonstrates that Si/TiO 2 nanocomposites with ultra-low silicon content and reduced energy input represent promising, energy-efficient photocatalysts for sustainable water treatment and environmental remediation applications.

• Ousdal, Erlend Lemva; Bathen, Marianne Etzelmüller; Medeiros, Helton Goncalves de; Galeckas, Augustinas; Kumar, Piyush & Martins, Maria I.M. [Vis alle 10 forfattere av denne artikkelen] (2026). Control and tuning of color centers in 4H silicon carbide by application of electric field via Schottky diode. Materials Science in Semiconductor Processing. ISSN 1369-8001. 201. doi: 10.1016/j.mssp.2025.110097. Fulltekst i vitenarkiv Vis sammendrag

  The ability to tune and manipulate the energy and intensity of photons emitted from color centers in semiconductors is of great importance for developing point defect quantum emitters as a platform for future quantum technology (QT) applications. One of the promising materials to realize point defect based QT is silicon carbide (SiC), as it combines a plethora of color center candidates with mature material processing and device fabrication. Here we explore the use of a Schottky diode, fabricated on a highly doped n-type 4H-SiC epitaxial layer, to control and modulate defect-related emission under both forward and reverse bias conditions. Zero phonon lines (ZPLs) from three prominent color centers are investigated: V1, V1’ and V2 assigned to the silicon vacancy, B1 and B2 from the carbon antisite-vacancy pair, and PL4 of the divacancy complex. All the studied defect-related emission wavelengths are found to shift in response to applied bias, but with a varying magnitude and direction of the shift. The electric field-induced variations are assigned to Stark effect and current flow within the device. Furthermore, two unknown defect signatures, labeled K1 and K2, are observed in the vicinity (within 2 meV) of the V2 ZPL and exhibit a strong forward bias dependence. A possible origin related to silicon vacancies perturbed by nearby carbon antisites is discussed.

• Zayim, E; Mohseni, A.; Galeckas, Augustinas; Sartori, Sabrina; Ernazarov, U & Karazhanov, Smagul (2025). Fabrication of tungsten oxide-based hybrid photochromic blends by scalable method. Materials Chemistry and Physics. ISSN 0254-0584. 337. doi: 10.1016/j.matchemphys.2025.130572. Fulltekst i vitenarkiv Vis sammendrag

  In this paper we have synthesized tungsten oxide-based organic/inorganic hybrid materials composed of tungsten hexachloride (WCl6) and polyvinylpyrrolidone (PVP) micro- and nanosized fibers. The films are deposited on substrates such as paper, glass, metal, and fabric using techniques including electrospinning, spin coating, fiber drawing, casting, and inkjet printing methods. The films exhibit photochromic properties at room temperature. Distinct from pure WO3-based coatings, photochromism of the hybrid films is reversible at ambient conditions without heating or applying an electric field. Photochromic performance of the hybrid films has been studied. From optical properties studies we demonstrate about UV illumination-induced band gap engineering. Mechanism of the photochromic effect in the hybrid films is suggested to be related to defects. We suggest also that illumination with the UV light undergoes by structural point defect formation.

• Azarov, Alexander; Radu, Cristian; Galeckas, Augustinas; Mercioniu, Ionel Florinel; Cernescu, Adrian & Venkatachalapathy, Vishnukanthan [Vis alle 11 forfattere av denne artikkelen] (2025). Self-Assembling of Multilayered Polymorphs with Ion Beams. Nano Letters. ISSN 1530-6984. 25(4), s. 1637–1643. doi: 10.1021/acs.nanolett.4c05727. Fulltekst i vitenarkiv
• Martinella, Corinna; Bathen, Marianne Etzelmüller; Galeckas, Augustinas & Grossner, Ulrike (2025). Formation of extended defects in heavy-ion-degraded SiC power MOSFETs. APL Materials. 13(5). doi: 10.1063/5.0258995. Fulltekst i vitenarkiv Vis sammendrag

  Silicon carbide (SiC) power devices offer distinct advantages over silicon-based technology and are envisioned to be of great benefit also for space applications. However, their reliability in space is reduced due to the high susceptibility to space-radiation, where single event effects (SEEs) induced by heavy ions are a particular risk. This work focuses on identifying the microscopic origin of a specific non-destructive SEE in SiC power MOSFETs known as single event leakage current (SELC), characterized by a permanent degradation of the gate and drain leakage currents and observed at a relatively low blocking voltage during heavy-ion exposure. The effect investigated is categorized as SELC II, and devices exposed to both broad-beam and microbeam of heavy-ions are studied herein. Using imaging photoluminescence spectroscopy, we observe distinct bright-spots after heavy-ion irradiation, containing spectral features that indicate the formation of stacking faults during exposure and subsequent biasing.

• Jagerová, Adéla; Malinský, Petr; Sofer, Zdeněk; Plutnarová, Iva; Vronka, Marek & Azarov, Alexander [Vis alle 8 forfattere av denne artikkelen] (2024). Evolution of Au nanoparticles in c-plane GaN under the heavy ion implantation and their optical properties. Journal of Alloys and Compounds. ISSN 0925-8388. 986. doi: 10.1016/j.jallcom.2024.174035. Fulltekst i vitenarkiv
• Slusar, Tetiana; Azarov, Alexander; Galeckas, Augustinas; Hallén, Anders; Ju, Jung Jin & Moon, Kiwon [Vis alle 7 forfattere av denne artikkelen] (2024). Er:LiNbO3 Quantum Memory Platform Optimized with Dynamic Defect Annealing. Advanced Optical Materials. doi: 10.1002/adom.202401374. Fulltekst i vitenarkiv Vis sammendrag

  Lithium niobate (LiNbO3) exhibits poor radiation resistance when conventionally implanted with Er at room temperature. To repair the structural disorder, high-temperature post-implantation anneals are typically required; however, such treatments can cause sample cracking and dopant redistribution, which are incompatible with device applications. The optimized approach is proposed by performing implants at elevated but acceptably low temperatures to in situ minimize the structural defects generated in the collision cascades, via so-called “dynamic defect annealing”. Thus, a gradual increase in Er optical activity is shown as a function of irradiation temperature in the range of 25–450 °C, in striking correlation with a decreasing trend for the residual disorder. The impact of moderate post-implantation anneals is also investigated by comparing the results of anneals of samples implanted at 25 °C and 450 °C. This comparison further confirms the higher optical activation of Er and lower residual structural disorder when the material is initially implanted at elevated temperatures. Based on these data, it is concluded that the use of dynamic defect annealing during the Er implantation of LiNbO3 is a promising strategy for optimizing it as a quantum memory platform, resolving otherwise inevitable trade-offs.

• Azarov, Alexander; Galeckas, Augustinas; Wendler, Elke; Monakhov, Eduard & Kuznetsov, Andrej (2024). Inverse dynamic defect annealing in ZnO. Applied Physics Letters. ISSN 0003-6951. 124(4). doi: 10.1063/5.0184669. Fulltekst i vitenarkiv Vis sammendrag

  Radiation tolerance of semiconductors depends on the dynamic defect annealing efficiency during irradiation. Consequently, it matters at what temperature one keeps the sample during irradiation, so that elevated temperatures typically result in lower remaining disorder. In the present work, we observed an opposite trend for the nitrogen ion implants into zinc oxide. Combining ion channeling technique, x-ray diffraction, and photoluminescence spectroscopy, we demonstrate that the interaction of nitrogen with radiation defects promotes an inverse dynamic annealing process, so that the increase in irradiation temperature leads to a more efficient defect formation. As a result, the residual radiation disorder is maximized at 650 °C and this state is characterized by the appearance of prominent optical signatures associated with zinc interstitials and strongly reduced strain accumulation as compared to the samples implanted at lower temperatures. However, for higher implantation temperatures, the impact of the inverse annealing decreases correlating with the surface degradation and loss of nitrogen.

• Hommedal, Ylva Knausgård; Frodason, Ymir Kalmann; Galeckas, Augustinas; Vines, Lasse & Johansen, Klaus Magnus H (2024). Broad luminescence from Zn acceptors in Zn doped β-Ga2O3. APL Materials. 12. doi: 10.1063/5.0190156. Fulltekst i vitenarkiv
• Azarov, Alexander; Galeckas, Augustinas; Cora, Ildikó; Fogarassy, Zsolt; Venkatachalapathy, Vishnukanthan & Monakhov, Eduard [Vis alle 7 forfattere av denne artikkelen] (2024). Optical Activity and Phase Transformations in γ/β Ga2O3 Bilayers Under Annealing. Advanced Optical Materials. doi: 10.1002/adom.202401325. Fulltekst i vitenarkiv Vis sammendrag

  Gallium oxide (Ga2O3) can be crystallized in several polymorphs exhibiting different physical properties. In this work, polymorphic structures consisting of the cubic defective spinel (γ) film on the top of the monoclinic (β) substrate are fabricated by disorder-induced ordering, known to be a practical way to stack these polymorphs together. Such bilayer structures are annealed to investigate optical properties and phase transformations. Specifically, photoluminescence and diffuse reflectance spectroscopy are combined with transmission electron microscopy, Rutherford backscattering/channeling spectrometry and X-ray diffraction to monitor the evolutions. As a result, a two-stage annealing kinetics is observed in γ/β Ga2O3 bilayers associated with the epitaxial γ-to-β regrowth at the interface at temperatures below 700 °C and a non-planar γ-to-β phase transformation starting at higher temperatures. Thus, the present data enhance understanding of the polymorphism in Ga2O3, interconnecting the phase transformation kinetics with the evolution of the optical properties.

• Ousdal, Erlend Lemva; Bathen, Marianne Etzelmüller; Galeckas, Augustinas; Kuznetsov, Andrej & Vines, Lasse (2024). Formation and stability of point defect color centers in 6H silicon carbide. Journal of Applied Physics. ISSN 0021-8979. 135(22). doi: 10.1063/5.0205832. Fulltekst i vitenarkiv Vis sammendrag

  Point defect color centers acting as single-photon emitters are promising for quantum technology applications and have been extensively studied, e.g., in the 4H polytype of silicon carbide (SiC). However, the physics of such color centers in other SiC polytypes is much less explored. Herein, we study the formation and thermal stability of such color centers in 6H-SiC using photoluminescence spectroscopy. The emissions from typical single-photon emitters, such as silicon vacancies, divacancies, and carbon antisite-vacancy pairs in 6H-SiC, were monitored as a function of the proton irradiation fluence and post-irradiation annealing, and compared to that in 4H-SiC. Overall, at the background of similarities between the emission behavior in 4H- and 6H-SiC polytypes, we observed prominent differences; e.g., for the thermal stability of the carbon antisite-vacancy pair, which exhibited maximized emissions upon 300 and 900  *C anneals in 4H- and 6H-SiC, respectively. Moreover, we observed a range of defect emission signatures not previously reported for 6H-SiC in the literature and discussed their potential origin in the context of the thermal stability. For example, among the PL-lines in 6H-SiC, we detected periodically repeatable emission signatures, resembling the so-called L-lines recently reported in 4H-SiC, even though their exact origin has not yet been settled in the literature. Thus, we use color centers comparison in different polytypes to better understand the nature of the single-photon emitters in SiC.

• Bathen, Marianne Etzelmüller; Karsthof, Robert Michael; Galeckas, Augustinas; Kumar, Piyush; Kuznetsov, Andrej & Grossner, Ulrike [Vis alle 7 forfattere av denne artikkelen] (2024). Impact of carbon injection in 4H-SiC on defect formation and minority carrier lifetime. Materials Science in Semiconductor Processing. ISSN 1369-8001. 176. doi: 10.1016/j.mssp.2024.108316. Fulltekst i vitenarkiv
• Zhu, Rui; Kuznetsov, Andrej; Galeckas, Augustinas; Zhang, Yonghui; Liang, Huili & Zhang, Guangyu [Vis alle 7 forfattere av denne artikkelen] (2024). Novel Photosensitive Dielectric-Based Image Sensor with Both High Signal-to-Noise Ratio and High Fill Factor. ACS Photonics. s. 555–562. doi: 10.1021/acsphotonics.4c02229. Fulltekst i vitenarkiv Vis sammendrag

  Driven by the pursuit of a higher signal-to-noise ratio (SNR), CMOS imagers have evolved from initial passive pixel sensor (PPS) with one transistor (1T) to 3T, 4T, or 5T active pixel sensors (APS) and then recently to digital pixel sensors (DPS). However, this evolution inevitably causes a lower and lower fill factor. Here, we innovatively designed a photodetector (PD) based on a photosensitive dielectric (PSD) strategy. The unique PSD layer works as an insulator in the dark and as a semiconductor under illumination, making the PD have a built-in 4T function consisting of memory, address, amplification, and reset. Further, we prepared a 16 × 16 one-PD (1D) APS array demo. The memory imaging, continuous imaging, power-off imaging, and trajectory tracing imaging functionalities were successfully demonstrated. This work provides a novel 1D APS structure with a built-in 4T function well handling the SNR-fill factor trade-off, paving a new path for a high-performance image sensor with good versatility and scalability.

• Azarov, Alexander; Galeckas, Augustinas; Mikhaylov, Alexey; Nikolskaya, Alena; Tetelbaum, David & Korolev, Dmitry [Vis alle 8 forfattere av denne artikkelen] (2024). Defect evolution and nitrogen incorporation in ion-implanted β-Ga2O3. Applied Physics Letters. ISSN 0003-6951. 125(19). doi: 10.1063/5.0239899. Fulltekst i vitenarkiv Vis sammendrag

  Nitrogen plays an important role in the Ga2O3-based device fabrication since it demonstrates a deep acceptor behavior and it can be used as a compensation impurity. In the present work, we introduced N into the monoclinic β-Ga2O3 single crystals by ion implantation using different dose-rates. The thermal evolution of the structural and optical properties of the implanted samples was studied by combining Rutherford backscattering/channeling spectrometry and x-ray diffraction with photoluminescence spectroscopy. We demonstrate that crystal disorder in N-implanted β-Ga2O3 is a strong function of ion flux even for room temperature implantation. Unlike other implanted species, the defect annealing kinetics for N exhibit a distinct two-stage behavior, where the low-temperature stage (<400 °C) is characterized by a rapid defect annealing, whereas the radiation defects exhibit a very slow evolution at the elevated temperatures (>400 °C). These trends are discussed in the framework of the disorder stabilization induced by the incorporation of the implanted N atoms into the Ga2O3 lattice. The obtained results can be used to better understand the interaction between N and intrinsic defects as well as to push forward the development of β-Ga2O3-based electronic devices.

• Frodason, Ymir Kalmann; Galeckas, Augustinas; Olsen, Vegard Skiftestad; Weiser, Philip Michael; Galazka, Zbigniew & Walle, Chris G. Van De [Vis alle 7 forfattere av denne artikkelen] (2024). Intrinsic origins of broad luminescence in melt-grown ZnGa2 O4 single crystals. PHYSICAL REVIEW MATERIALS. 8(9). doi: 10.1103/PhysRevMaterials.8.094604. Fulltekst i vitenarkiv
• Macková, Anna; Jagerová, Adéla; Lalik, Ondrej; Mikšová, Romana; Poustka, David & Mistrík, Jan [Vis alle 12 forfattere av denne artikkelen] (2023). Combined Au/Ag nanoparticle creation in ZnO nanopillars by ion implantation for optical response modulation and photocatalysis. Applied Surface Science. ISSN 0169-4332. 610, s. 1–13. doi: 10.1016/j.apsusc.2022.155556. Fulltekst i vitenarkiv Vis sammendrag

  ZnO nanopillars were implanted with Au-400 keV and Ag-252 keV ions with ion fluences from 1 × 1015 cm−2 to 1 × 1016 cm−2. We compared ZnO nanopillars solely implanted with Au-ions and dually-implanted with Au and Ag-ions. Rutherford Back-Scattering spectrometry (RBS) confirmed Ag and Au embedded in ZnO nanopillar layers in a reasonable agreement with theoretical calculations. A decreasing thickness of the ZnO nanopillar layer was evidenced with the increasing ion implantation fluences. Spectroscopic Ellipsometry (SE) showed a decrease of refractive index in the nanopillar parts with embedded Au, Ag-ions. XRD discovered vertical domain size decreasing with the proceeding radiation damage accumulated in ZnO nanopillars which effect was preferably ascribed to Au-ions. SE and diffuse reflectance spectroscopy (DRS) showed optical activity of the created nanoparticles at wavelength range 500 – 600 nm and 430 – 700 nm for the Au-implanted and Au, Ag-implanted ZnO nanopillars, respectively. Photoluminescence (PL) features linked to ZnO deep level emission appear substantially enhanced due to plasmonic interaction with metal nanoparticles created by Ag, Au-implantation. Photocatalytic activity seems to be more influenced by the nanoparticles presented in the layer rather than the surface morphology. Dual implantation with Ag, Au-ions enhanced optical activity to a larger extent without significant morphology deterioration as compared to the solely Au-ion implanted nanopillars.

• Kjeldby, Snorre Braathen; Nguyen, Phuong Dan; Fernández, Javier García; Haug, Kristian; Galeckas, Augustinas & Jensen, Ingvild Julie Thue [Vis alle 9 forfattere av denne artikkelen] (2023). Optical properties of ZnFe2O4 nanoparticles and Fe-decorated inversion domain boundaries in ZnO. Nanoscale Advances. 5(7), s. 2102–2110. doi: 10.1039/d2na00849a. Fulltekst i vitenarkiv Vis sammendrag

  The maximum efficiency of solar cells utilizing a single layer for photovoltaic conversion is given by the single junction Shockley–Queisser limit. In tandem solar cells, a stack of materials with different band gaps contribute to the conversion, enabling tandem cells to exceed the single junction Shockley–Queisser limit. An intriguing variant of this approach is to embed semiconducting nanoparticles in a transparent conducting oxide (TCO) solar cell front contact. This alternative route would enhance the functionality of the TCO layer, allowing it to participate directly in photovoltaic conversion via photon absorption and charge carrier generation in the nanoparticles. Here, we demonstrate the functionalization of ZnO through incorporation of either ZnFe2O4 spinel nanoparticles (NPs) or inversion domain boundaries (IDBs) decorated by Fe. Diffuse reflectance spectroscopy and electron energy loss spectroscopy show that samples containing spinel particles and samples containing IDBs decorated by Fe both display enhanced absorption in the visible range at around 2.0 and 2.6 eV. This striking functional similarity was attributed to the local structural similarity around Fe-ions in spinel ZnFe2O4 and at Fe-decorated basal IDBs. Hence, functional properties of the ZnFe2O4 arise already for the two-dimensional basal IDBs, from which these planar defects behave like two-dimensional spinel-like inclusions in ZnO. Cathodoluminescence spectra reveal an increased luminescence around the band edge of spinel ZnFe2O4 when measuring on the spinel ZnFe2O4 NPs embedded in ZnO, whereas spectra from Fe-decorated IDBs could be deconvoluted into luminescence contributions from bulk ZnO and bulk ZnFe2O4.

• Kang, Xiaolan; Reinertsen, Vilde Mari; Both, Kevin Gregor; Galeckas, Augustinas; Aarholt, Thomas & Prytz, Øystein [Vis alle 9 forfattere av denne artikkelen] (2022). Galvanic Restructuring of Exsolved Nanoparticles for Plasmonic and Electrocatalytic Energy Conversion. Small. ISSN 1613-6810. 18(29). doi: 10.1002/smll.202201106. Fulltekst i vitenarkiv Vis sammendrag

  There is a growing need to control and tune nanoparticles (NPs) to increase their stability and effectiveness, especially for photo- and electrochemical energy conversion applications. Exsolved particles are well anchored and can be re-shaped without changing their initial location and structural arrangement. However, this usually involves lengthy treatments and use of toxic gases. Here, the galvanic replacement/deposition method is used, which is simpler, safer, and leads to a wealth of new hybrid nanostructures with a higher degree of tailorability. The produced NiAu bimetallic nanostructures supported on SrTiO3 display exceptional activity in plasmon-assisted photoelectrochemical (PEC) water oxidation reactions. In situ scanning transmission electron microscopy is used to visualize the structural evolution of the plasmonic bimetallic structures, while theoretical simulations provide mechanistic insight and correlate the surface plasmon resonance effects with structural features and enhanced PEC performance. The versatility of this concept in shifting catalytic modes to the hydrogen evolution reaction is demonstrated by preparing hybrid NiPt bimetallic NPs of low Pt loadings on highly reduced SrTiO3 supports. This powerful methodology enables the design of supported bimetallic nanomaterials with tunable morphology and catalytic functionalities through minimal engineering.

• Azarov, Alexander; Galeckas, Augustinas; Ling, Francis Chi-Chung & Kuznetsov, Andrej (2022). Tuning defect-related optical bands by channeling implants in semiconductors. Journal of Physics D: Applied Physics. ISSN 0022-3727. 56(3). doi: 10.1088/1361-6463/aca778. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Ion implantation is an excellent method to introduce defects into semiconductors, extending their functionalities in a controllable way. Herein, we investigated an option to use crystallographically aligned implants as an additional route to control the balance between optically active defects, selecting ZnO as a test material. The optical data were correlated with the structural analysis confirming the formation of different dominating crystalline defects in samples implanted along and off [0001] direction. Specifically, we demonstrated that different proportions in the contents of the extended and point defects in the initial as-implanted states of these samples, lead to prominent variations in the defect-related luminescence upon annealing. As such, we conclude that channeling implants may have an added value in the functionalization of defects in semiconductors, e.g. to tune specific spectral contents in the defect-related emission bands.

• Galeckas, Augustinas; Karsthof, Robert Michael; Kingsly, Gana; Kok, Angela; Bathen, Marianne Etzelmüller & Vines, Lasse [Vis alle 7 forfattere av denne artikkelen] (2022). Cross-Sectional Carrier Lifetime Profiling and Deep Level Monitoring in Silicon Carbide Films Exhibiting Variable Carbon Vacancy Concentrations. Physica Status Solidi (a) applications and materials science. ISSN 1862-6300. s. 1–7. doi: 10.1002/pssa.202200449. Fulltekst i vitenarkiv Vis sammendrag

  The carrier lifetime control over 150 μm thick 4H-SiC epitaxial layers via thermal generation and annihilation of carbon vacancy (VC) related Z1/2 lifetime killer sites is reported. The defect developments upon typical SiC processing steps, such as high- and moderate-temperature anneals in the presence of a carbon cap, are monitored by combining electrical characterization techniques capable of VC depth-profiling, capacitance–voltage (CV) and deep-level transient spectroscopy (DLTS), with a novel all-optical approach of cross-sectional carrier lifetime profiling across 4H-SiC epilayer/substrate based on imaging time-resolved photoluminescence (TRPL) spectroscopy in orthogonal pump-probe geometry, which readily exposes in-depth efficacy of defect reduction and surface recombination effects. The lifetime control is realized by initial high-temperature treatment (1800 °C) to increase VC concentration to ≈1013 cm−3 level followed by a moderate-temperature (1500 °C) post-annealing of variable duration under C-rich thermodynamic equilibrium conditions. The post-annealing carried out for 5 h in effect eliminates VC throughout the entire ultra-thick epilayer. The reduction of VC-related Z1/2 sites is proven by a significant lifetime increase from 0.8 to 2.5 μs. The upper limit of lifetimes in terms of carrier surface leakage and the presence of other nonradiative recombination centers besides Z1/2, possibly related to residual impurities such as boron are discussed.

• Karsthof, Robert Michael; Frodason, Ymir Kalmann; Galeckas, Augustinas; Weiser, Philip Michael; Zviagin, Vitaly & Grundmann, Marius (2022). Light Absorption and Emission by Defects in Doped Nickel Oxide. Advanced Photonics Research. ISSN 2699-9293. 3(11). doi: 10.1002/adpr.202200138. Fulltekst i vitenarkiv
• Macková, Anna; Malinský, Petr; Jagerová, Adéla; Mikšová, Romana; Lalik, Ondrej & Nekvindová, Pavla [Vis alle 14 forfattere av denne artikkelen] (2022). Energetic Au ion beam implantation of ZnO nanopillars for optical response modulation. Journal of Physics D: Applied Physics. ISSN 0022-3727. 55(215101). doi: 10.1088/1361-6463/ac5486. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Nanopillars of ZnO were implanted with Au-400 keV ions at various ion fluences from 1 × 10 15 cm −2 to 1 × 10 16 cm −2 and subsequently annealed at 750 °C for 15 min in order to reduce the implantation damage and to support Au nanoparticle (NP) aggregation. It was found that implantation-induced effects and thermal effects influence the Au NP coalescence as well as the quality of the ZnO nanopillars. Rutherford Back-Scattering spectrometry (RBS) showed the broader Au-depth profiles than it was theoretically predicted, but the Au-concentration maximum agrees well with prediction taking into account the effective ZnO layer density. The implantation at the higher fluences induced the morphology modification of the nanopillar layer evidenced by RBS and scanning electron microscopy (SEM). An indirect evidence of this effect was given by optical ellipsometry due to gradual refractive index changes in the ZnO nanopillars with the increased Au-ion fluence. Optical characterization of the Au-implanted and annealed nanopillars performed by means of photoluminescence (PL) and diffuse-reflectance spectroscopy (DRS) evidenced the surface plasmon resonance (SPR) activity of the embedded Au NPs. The SPR-enhanced scattering and PL emission observed in the spectral range 500–650 nm are ascribed to Au NPs or more complex Au-clusters. In addition, the ellipsometry measurements of extinction coefficient are found to corroborate well results from DRS, both indicating increase of SPR effect with the increase of Au-ion fluence and after the post-annealing.

• Aarseth, Bjørn Lupton; Granerød, Cecilie Skjold; Galeckas, Augustinas; Azarov, Alexander; Nguyen, Phuong Dan & Prytz, Øystein [Vis alle 7 forfattere av denne artikkelen] (2021). Formation and functionalization of Ge-nanoparticles in ZnO. Nanotechnology. ISSN 0957-4484. 32(50). doi: 10.1088/1361-6528/ac264a. Fulltekst i vitenarkiv Vis sammendrag

  Semiconductor nanocrystals are often proposed as a viable route to improve solar energy conversion in photovoltaics and photoelectrochemical systems. Embedding the nanocrystals in, e.g. a transparent and conducting electrode of a solar cell will promote the photon absorption and subsequent transfer of the generated charge carriers from the nanocrystal, and thereby enhance the function of the electrode. This can be accomplished by embedding a semiconducting nanocrystal with a small bandgap in a transparent conducting oxide (TCO), which is commonly utilized as electrode in new generation solar cells. Here, we demonstrate the incorporation, formation, and functionalization of germanium (Ge) nanocrystals in zinc oxide utilizing ion implantation, where post implantation annealing at 800 °C results in diamond cubic Ge nanocrystals with sizes between 2 and 20 nm. Photoluminecence spectra show a distinct emission around 0.7 eV arising from the Ge nanocrystals, and with additional emission features up to 1.15 eV due to quantum confinement, demonstrating a novel functionalization and tunability of the TCO electrode.

• Rauwel, Protima; Galeckas, Augustinas & Rauwel, Erwan (2021). Enhancing the UV emission in ZnO-CNT hybrid nanostructures via the surface plasmon resonance of Ag nanoparticles. Nanomaterials. 11(2), s. 452–463. doi: 10.3390/nano11020452. Fulltekst i vitenarkiv Vis sammendrag

  The crystal quality and surface states are two major factors that determine optical properties of ZnO nanoparticles (NPs) synthesized through nonaqueous sol–gel routes, and both are strongly dependent on the growth conditions. In this work, we investigate the influence of the different growth temperatures (240 and 300 °C) on the morphology, structural and crystal properties of ZnO NP. The effects of conjoining ZnO NP with carbon nanotubes (CNT) and the role of surface states in such a hybrid nanostructure are studied by optical emission and absorption spectroscopy. We demonstrate that depending on the synthesis conditions, activation or passivation of certain surface states may occur. Next, silver nanoparticles are incorporated into ZnO–CNT nanostructures to explore the plasmon–exciton coupling effect. The observed enhanced excitonic and suppressed defect-related emissions along with blue-shifted optical band gap suggest an intricate interaction of Burstein–Moss, surface plasmon resonance and surface band-bending effects behind the optical phenomena in hybrid ZnO–CNT–Ag nanocomposites.

• Kang, Xiaolan; Berberidou, Chrysanthi; Galeckas, Augustinas; Bazioti, Kalliopi; Sagstuen, Einar & Norby, Truls Eivind [Vis alle 8 forfattere av denne artikkelen] (2021). Visible Light Driven Photocatalytic Decolorization and Disinfection of Water Employing Reduced TiO2 Nanopowders. Catalysts. 11(2). doi: 10.3390/catal11020228. Fulltekst i vitenarkiv Vis sammendrag

  Defect-engineering of TiO2 can have a major impact on its photocatalytic properties for the degradation of persisting and non-biodegradable pollutants. Herein, a series of intrinsic and extrinsic defects are induced by post annealing of crystalline TiO2 under different reducing atmospheres. A detailed optoelectronic characterization sheds light on the key characteristics of the defect-engineered TiO2 nanopowders that are linked to the photocatalytic performance of the prepared photocatalysts. The photodegradation of a model dye, malachite green, as well as the inactivation of bacterial endospores of the Geobacillus stearothermophilus species were studied in the presence of the developed catalysts under visible light illumination. Our results indicate that a combination of certain defects is necessary for the improvement of the photocatalytic process for water purification and disinfection under visible light.

• Kang, Xiaolan; Chaperman, Larissa; Galeckas, Augustinas; Ammar, Souad; Mammeri, Fayna & Norby, Truls [Vis alle 7 forfattere av denne artikkelen] (2021). Water Vapor Photoelectrolysis in a Solid-State Photoelectrochemical Cell with TiO2 Nanotubes Loaded with CdS and CdSe Nanoparticles. ACS Applied Materials & Interfaces. ISSN 1944-8244. 13(39), s. 46875–46885. doi: 10.1021/acsami.1c13047. Fulltekst i vitenarkiv Vis sammendrag

  In this study, polyol-made CdS and CdSe crystalline nanoparticles (NPs) are loaded by impregnation on TiO2 nanotube arrays (TNTAs) for solar-simulated light-driven photoelectrochemical (PEC) water vapor splitting. For the first time, we introduce a safe way to utilize toxic, yet efficient photocatalysts by integration in solid-state PEC (SSPEC) cells. The enabling features of SSPEC cells are the surface protonic conduction mechanism on TiO2 and the use of polymeric electrolytes, such as Nafion instead of liquid ones, for operation with gaseous reactants, like water vapor from ambient humidity. Herein, we studied the effects of both the operating conditions in gaseous ambient atmospheres and the surface modifications of TNTAs-based photoanodes with well-crystallized CdS and CdSe NPs. We showed 3.6 and 2.5 times increase in the photocurrent density of defective TNTAs modified with CdS and CdSe, respectively, compared to the pristine TNTAs. Electrochemical impedance spectroscopy and structural characterizations attributed the improved performance to the higher conductivity induced by intrinsic defects as well as to the enhanced electron/hole separation at the TiO2/CdS heterojunction under gaseous operating conditions. The SSPEC cells were evaluated by cycling between high relative humidity (RH) (80%) and low RH levels (40%), providing direct evidence of the effect of RH and, in turn, adsorbed water, on the cell performance. Online mass spectrometry indicated the corresponding difference in the H2 production rate. In addition, a complete restoration of the SSPEC cell performance from low to high RH levels was also achieved. The presented system can be employed in off-grid, water depleted, and air-polluted areas for the production of hydrogen from renewable energy and provides a solution for the safe use of toxic, yet efficient photocatalysts.

• Olsen, Vegard Skiftestad; Øversjøen, Vetle; Gogova-Petrova, Daniela; Pecz, Bela; Galeckas, Augustinas & Borgersen, Jon Arthur [Vis alle 9 forfattere av denne artikkelen] (2021). ZnSnN2 in Real Space and k-Space: Lattice Constants, Dislocation Density, and Optical Band Gap. Advanced Optical Materials. doi: 10.1002/adom.202100015. Fulltekst i vitenarkiv
• Bathen, Marianne Etzelmüller; Galeckas, Augustinas; Karsthof, Robert Michael; Delteil, Aymeric; Sallet, Vincent & Kuznetsov, Andrej [Vis alle 7 forfattere av denne artikkelen] (2021). Resolving Jahn-Teller induced vibronic fine structure of silicon vacancy quantum emission in silicon carbide. Physical review B (PRB). ISSN 2469-9950. 104. doi: 10.1103/PhysRevB.104.045120. Fulltekst i vitenarkiv Vis sammendrag

  Point defects in semiconductors are promising single-photon emitters (SPEs) for quantum computing, communication, and sensing applications. However, factors such as emission brightness, purity. and indistinguishability are limited by interactions between localized defect states and the surrounding environment. Therefore, it is important to map the full emission spectrum from each SPE, to understand the complex interplay between the different defect configurations, their surroundings, and external perturbations. Herein, we investigate a family of regularly spaced sharp luminescence peaks appearing in the near-infrared portion of photoluminescence (PL) spectra from n-type 4H-SiC samples after irradiation. This periodic emitter family, labeled the L lines, is only observed when the zero-phonon line signatures of the negatively charged Si vacancy (so-called V lines) are present. The L lines appear with 1.45meV and 1.59meV energy spacing after H and He irradiation and increase linearly in intensity with fluence—reminiscent of the intrinsic defect trend. Furthermore, we monitor the dependence of the L-line emission energy and intensity on heat treatments, electric field strength, and PL collection temperature, discussing these data in the context of the L lines. Based on the strong similarity between the irradiation, electric field, and thermal responses of the L and V lines, the L lines are attributed to the Si vacancy in 4H-SiC. The regular and periodic appearance of the L lines provides strong arguments for a vibronic origin explaining the oscillatory multipeak spectrum. To account for the small energy separation of the L lines, we propose a model based on rotations of distortion surrounding the Si vacancy driven by a dynamic Jahn-Teller effect.

• Kjeldstad, Torunn; Thøgersen, Annett; Stange, Marit Synnøve Sæverud; Jensen, Ingvild Julie Thue; Nilsen, Ola & Galeckas, Augustinas [Vis alle 7 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Woerle, Judith; Bathen, Marianne Etzelmüller; Prokscha, Thomas; Galeckas, Augustinas; Ayedh, Hussein Mohammed Hussein & Vines, Lasse [Vis alle 7 forfattere av denne artikkelen] (2020). Muon Interaction with Negative-U and High-Spin-State Defects: Differentiating Between C and Si Vacancies in 4H-SiC. Physical Review Applied. 14. doi: 10.1103/PhysRevApplied.14.054053. Fulltekst i vitenarkiv Vis sammendrag

  Low-energy muon-spin-rotation spectroscopy (LE-μSR) is employed to study silicon and carbon vacancies in proton-irradiated 4H-SiC. We show that the implanted muon is quickly attracted to the negative Si vacancy (VSi), where it forms a paramagnetic muonium (Mu0) state, resulting in a reduction of the diamagnetic fraction. In samples with predominantly C vacancies (VC), on the other hand, the formation of Mu0 is very short lived and the muon quickly captures a second electron to form a diamagnetic Mu− state. The results are corroborated by density-functional calculations, where significant differences in the relaxation mechanism of the nearest-neighbor dangling bonds of the vacancies are discussed. We propose that the LE-μSR technique is capable of differentiating between high-spin and negative-U behavior in semiconducting materials. Finally, our findings emphasize the large potential of LE-μSR to probe near-surface semiconductor defects, a capability that is crucial for further development of many electronic and quantum technology applications.

• Karsthof, Robert Michael; Bathen, Marianne Etzelmüller; Galeckas, Augustinas & Vines, Lasse (2020). Conversion pathways of primary defects by annealing in proton-irradiated n-type 4H-SiC. Physical review B (PRB). ISSN 2469-9950. 102(18). doi: 10.1103/PhysRevB.102.184111. Fulltekst i vitenarkiv Vis sammendrag

  The development of defect populations after proton irradiation of n-type 4H-SiC and subsequent annealing experiments is studied by means of deep level transient (DLTS) and photoluminescence spectroscopy. A comprehensive model is suggested describing the evolution and interconversion of irradiation-induced point defects during annealing below 1000 ∘C. The model proposes the EH4 and EH5 traps frequently found by DLTS to originate from the (+/0) charge transition level belonging to different configurations of the carbon antisite-carbon vacancy (CAV) complex. Furthermore, we show that the transformation channel between the silicon vacancy (VSi) and CAV is effectively blocked under n-type conditions, but becomes available in samples where the Fermi level has moved towards the center of the band gap due to irradiation-induced donor compensation. The annealing of VSi and the carbon vacancy (VC) is shown to be dominated by recombination with residual self-interstitials at temperatures of up to 400 ∘C. Going to higher temperatures, a decay of the CAV pair density is reported which is closely correlated to a renewed increase of VC concentration. A conceivable explanation for this process is the dissociation of the CAV pair into separate carbon anitisites and VC defects. Lastly, the presented data supports the claim that the removal of free carriers in irradiated SiC is due to introduced compensating defects and not passivation of shallow nitrogen donors.

• Azarov, Alexander; Galeckas, Augustinas; Venkatachalapathy, Vishnukanthan; Mei, Zengxia; Du, Xiaolong & Monakhov, Eduard [Vis alle 7 forfattere av denne artikkelen] (2020). Acceptor complex signatures in oxygen-rich ZnO thin films implanted with chlorine ions. Journal of Applied Physics. ISSN 0021-8979. 128. doi: 10.1063/5.0021089. Fulltekst i vitenarkiv Vis sammendrag

  Spectroscopic identification of defects and impurities is crucial for understanding doping asymmetry issues in ZnO and, therefore, realization of true ZnO-based bipolar devices. Chlorine (Cl) is an amphoteric impurity in ZnO exhibiting acceptor behavior in the interstitial configuration and donor action once on substitutional oxygen sites (ClO). In its turn, the incorporation of Cl atoms depends on the material growth conditions and a ClO fraction should be suppressed in O-rich materials. In the present work, Cl ions were implanted into ZnO thin films synthesized under O-rich conditions. In contrast to a negligible effect of Cl incorporation to electrical conductivity, photoluminescence measurements revealed dramatic developments of optical properties with a strong acceptor-like spectral signature emerging after 900 °C anneals. We discuss the origins of a new excitonic I* line (3.355 eV) induced by Cl-implantation and propose two alternative defect models based on shallow acceptor and shallow donor complexes.

• Kumar, Raj; Bergum, Kristin; Riise, Heine Nygard; Monakhov, Eduard; Galeckas, Augustinas & Svensson, Bengt Gunnar (2020). Impact of post annealing and hydrogen implantation on functional properties of Cu2O thin films for photovoltaic applications. Journal of Alloys and Compounds. ISSN 0925-8388. 825(5), s. 1–8. doi: 10.1016/j.jallcom.2020.153982. Fulltekst i vitenarkiv Vis sammendrag

  Polycrystalline cuprous oxide (Cu2O) thin films were sputtered, annealed (900 °C rapid thermal annealing) and subsequently implanted with various hydrogen ion (H+) doses from 5E13 to 2E15 cm−2 with a low acceleration energy of 36 keV at room temperature to tailor the functional properties of the thin films for solar cell application. The annealed and H+ implanted Cu2O thin films were post annealed at low temperatures from 100 °C to 600 °C in an inert atmosphere to promote hydrogen passivation of prevalent intrinsic acceptors and tune the carrier concentration for optimum performance as an absorption layer in a heterojunction solar cell. The H+ incorporation and post annealing tuned the structural, optical and electrical properties of annealed polycrystalline Cu2O thin films. The results show an enhancement of the excitonic feature around ∼2.0 eV with H+ dose. The normalized photoluminescence (PL) area around ∼1.7 eV was drastically enhanced with increasing H+ doses compared to excitonic and copper vacancy related area. The normalized total PL quantum efficiency shows an enhancement in yield with elevated H+ doses by two orders of magnitude. The hole concentration decreases down to ∼1013 cm−3, while hole mobility and resistivity increase to ∼27 cm2/V and ∼2.4 kΩcm, respectively, as the H+ implantation goes from lower to higher doses. In addition, the post annealing and H+ incorporation lead to a change in the energy level of the major acceptor from 0.21 eV to 0.27 eV above the valence band maximum. By following the qualitative (PL analysis) and quantitative (Hall data) outcomes, we can conclude that H+ implantation and post annealing likely indicates the passivation of both acceptor defects and compensating donor defects.

• Azarov, Alexander; Galeckas, Augustinas; Mieszczyński, Cyprian; Hallen, Anders & Kuznetsov, Andrej (2020). Effects of annealing on photoluminescence and defect interplay in ZnO bombarded by heavy ions: Crucial role of the ion dose. Journal of Applied Physics. ISSN 0021-8979. 127. doi: 10.1063/1.5134011. Fulltekst i vitenarkiv Vis sammendrag

  Bombardment of ZnO with heavy ions generating dense collision cascades is of particular interest because of the formation of nontrivial damage distribution involving a defected layer located between the surface and the bulk damage regions, as seen by Rutherford backscattering spectroscopy in the channeling mode. By correlating photoluminescence and channeling data, we demonstrate that the thermal evolution of defects in wurtzite ZnO single crystals implanted with Cd ions strongly depends on the implanted dose. Specifically, the ion dose has a profound effect on the optical response in the spectral range between the near-band-edge emission and deep-level emission bands. The interplay between interstitial and vacancy type defects during annealing is discussed in relation to the evolution of the multipeak damage distribution.

• Vasquez, Geraldo Cristian; Johansen, Klaus Magnus H; Galeckas, Augustinas; Vines, Lasse & Svensson, Bengt Gunnar (2020). Optical signatures of single ion tracks in ZnO. Nanoscale Advances. 2(2), s. 724–733. doi: 10.1039/C9NA00677J. Fulltekst i vitenarkiv Vis sammendrag

  The optical properties of single ion tracks have been studied in ZnO implanted with Ge by combining depth-resolved hyperspectral cathodoluminescence (CL) and photoluminescence (PL) spectroscopy techniques. The results indicate that ZnO is susceptible to implantation doses as low as 108 to 109 cm−2. We demonstrate that the intensity ratio of ionized and neutral donor bound exciton emissions [D+X/D0X] can be used as a tracer for a local band bending both at the surface as well as in the crystal bulk along the ion tracks. The hyperspectral CL imaging performed at 80 K with 50 nm resolution over the regions with single ion tracks permitted direct assessment of the minority carrier diffusion length. The radii of distortion and space charge surrounding single ion tracks were estimated from the 2D distributions of defect-related green emission (GE) and excitonic D+X emission, both normalized with regard to neutral D0X emission, i.e., from the [GE/D0X] and [D+X/D0X] ratio maps. Our results indicate that single ion tracks in ZnO can be resolved up to ion doses of the order of 5 × 109 cm−2, in which defect aggregation along the extended defects obstructs signatures of individual tracks.

• Bathen, Marianne Etzelmüller; Galeckas, Augustinas; Coutinho, José & Vines, Lasse (2020). Influence of hydrogen implantation on emission from the silicon vacancy in 4H-SiC. Journal of Applied Physics. ISSN 0021-8979. 127(8). doi: 10.1063/1.5140659. Fulltekst i vitenarkiv Vis sammendrag

  The silicon vacancy (VSi) in 4H-SiC is a room temperature single-photon emitter with a controllable high-spin ground state and is a promising candidate for future quantum technologies. However, controlled defect formation remains a challenge, and, recently, it was shown that common formation methods such as proton irradiation may, in fact, lower the intensity of photoluminescence (PL) emission from VSi as compared to other ion species. Herein, we combine hybrid density functional calculations and PL studies of the proton-irradiated n-type 4H-SiC material to explore the energetics and stability of hydrogen-related defects, situated both interstitially and in defect complexes with VSi, and confirm the stability of hydrogen in different interstitial and substitutional configurations. Indeed, VSi-H is energetically favorable if VSi is already present in the material, e.g., following irradiation or ion implantation. We demonstrate that hydrogen has a significant impact on electrical and optical properties of VSi, by altering the charge states suitable for quantum technology applications, and provide an estimate for the shift in thermodynamic transition levels. Furthermore, by correlating the theoretical predictions with PL measurements of 4H-SiC samples irradiated by protons at high (400 C) and room temperatures, we associate the observed quenching of VSi emission in the case of high-temperature and high-fluence proton irradiation with the increased mobility of Hi, which may initiate VSi-H complex formation at temperatures above 400 C. The important implication of hydrogen being present is that it obstructs the formation of reliable and efficient single-photon emitters based on silicon vacancy defects in 4H-SiC.

• Vasquez, Geraldo Cristian; Bathen, Marianne Etzelmüller; Galeckas, Augustinas; Bazioti, Kalliopi; Johansen, Klaus Magnus H & Maestre, D. [Vis alle 11 forfattere av denne artikkelen] (2020). Strain Modulation of Si Vacancy Emission from SiC Micro- and Nanoparticles. Nano Letters. ISSN 1530-6984. 20(12), s. 8689–8695. doi: 10.1021/acs.nanolett.0c03472. Fulltekst i vitenarkiv Vis sammendrag

  Single-photon emitting point defects in semiconductors have emerged as strong candidates for future quantum technology devices. In the present work, we exploit crystalline particles to investigate relevant defect localizations, emission shifting, and waveguiding. Specifically, emission from 6H-SiC micro- and nanoparticles ranging from 100 nm to 5 μm in size is collected using cathodoluminescence (CL), and we monitor signals attributed to the Si vacancy (VSi) as a function of its location. Clear shifts in the emission wavelength are found for emitters localized in the particle center and at the edges. By comparing spatial CL maps with strain analysis carried out in transmission electron microscopy, we attribute the emission shifts to compressive strain of 2–3% along the particle a-direction. Thus, embedding VSi qubit defects within SiC nanoparticles offers an interesting and versatile opportunity to tune single-photon emission energies while simultaneously ensuring ease of addressability via a self-assembled SiC nanoparticle matrix.

• Kjeldstad, Torunn; Thøgersen, Annett; Stange, Marit Synnøve Sæverud; Azarov, Alexander; Monakhov, Eduard & Galeckas, Augustinas (2019). Monitoring selective etching of self-assembled nanostructured a-Si:Al films. Nanotechnology. ISSN 0957-4484. 30(13), s. 1–5. doi: 10.1088/1361-6528/aafb86. Fulltekst i vitenarkiv Vis sammendrag

  Nanoporous and nanowire structures based on silicon (Si) have a well recognized potential in a number of applications such as photovoltaics, energy storage and thermoelectricity. The immiscibility of Si and aluminum (Al) may be utilized to produce a thin film of vertically aligned Al nanowires of 5 nm diameter within an amorphous silicon matrix (a-Si), providing a cheap and scalable fabrication method for sub 5 nm size Si nanostructures. In this work we study functionalization of these structures by removal of the Al nanowires. The nanowires have been etched by an aqueous solution of HCl, which results in a structure of vertically aligned nanochannels in a-Si with admixture of SiO x . The removal of Al nanowires has been monitored by several electron microscopy techniques, x-ray diffraction, Rutherford backscattering spectroscopy, and optical reflectance. We have established that optical reflectance measurements can reliably identify the complete removal of Al, confirmed by other techniques. This provides a robust and relatively simple method for controlling the nano-fabrication process on a macroscopic scale.

• Schifano, Ramon; Jakiela, R; Galeckas, Augustinas; Kopalko, K; Herklotz, Frank & Johansen, Klaus Magnus H [Vis alle 7 forfattere av denne artikkelen] (2019). Role of intrinsic and extrinsic defects in H implanted hydrothermally grown ZnO. Journal of Applied Physics. ISSN 0021-8979. 126(12). doi: 10.1063/1.5115597. Fulltekst i vitenarkiv Vis sammendrag

  The impact of hydrogen in ZnO is revealed by combining reaction dynamics calculations with temperature dependent Hall (TDH), photoluminescence, and secondary ion mass spectrometry measurements performed on H, 2H, and He implanted ZnO. H and 2H box profiles with a concentration ranging from ∼3×1017 cm−3 to ∼1019 cm−3 and He to produce as much as damage as in the [H] ∼3×1017 cm−3 case were implanted in the samples. The formation of Li lean regions has been observed for [2H] <1019 cm−3 after annealing at 400 ∘C. This is attributed to Lii presence consequent to the diffusion of Zni created during the H/2H implantation process. Results extracted from the TDH measurements performed prior to the annealing at 400 ∘C evidence that Lii contributes to an increase in carrier concentration up to ∼1017 cm−3 by providing a donor level with an activation energy of ∼40 meV and thus is very close to the value of ∼47 meV expected for H in the oxygen site. The reaction dynamics analysis evidences that the amount of Lii introduced is decreasing at higher H implantation doses as a result of increasing VZn and H-VZn retrapping, reactions in which Lii is competing with H. Overall, due to Lii formation as well as the presence of Al the maximum percentage of the implanted H or 2H acting as a donor in the investigated range is found to be ≲ 2%, which is considerably lower than previously reported.

• Frodason, Ymir Kalmann; Johansen, Klaus Magnus H; Galeckas, Augustinas & Vines, Lasse (2019). Broad luminescence from donor-complexed LiZn and NaZn acceptors in ZnO. Physical review B (PRB). ISSN 2469-9950. 100(18). doi: 10.1103/PhysRevB.100.184102. Fulltekst i vitenarkiv Vis sammendrag

  Zn substitutional lithium ( Li Zn ) and sodium ( Na Zn ) acceptors and their complexes with common donor impurities ( Al Zn , Hi, and HO) in ZnO have been studied using hybrid functional calculations. The results show that the complexes are not exclusively charge neutral, but rather exhibit a thermodynamic ( + / 0 ) transition level close to the valence band maximum. The positive charge states are associated with a polaronic defect state, similar to those of the well-studied charge-neutral isolated acceptors. This incomplete passivation has profound consequences for the optical properties of the complexes. Indeed, electron transitions from the conduction band minimum to the ( + / 0 ) transition level of the complexes result in broad luminescence bands that are blueshifted with respect to those originating from the isolated acceptors. Such complexes are proposed as a potential defect origin of the green luminescence observed at the high-energy side of the orange luminescence band (caused by Li Zn ) in hydrothermally grown ZnO. This prediction is supported by experimental photoluminescence and secondary ion mass spectrometry data on a hydrothermally grown ZnO sample. We have also explored how the parameters controlling the fraction and screening of exchange in the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional influence the results by comparing two parametrization approaches: (i) the conventional one where the exchange fraction is adjusted to reproduce the experimental band gap, and (ii) tuning both parameters in order to also comply with the generalized Koopmans theorem (gKT). Interestingly, these approaches were found to yield similar results.

• Kjeldstad, Torunn; Thøgersen, Annett; Stange, Marit Synnøve Sæverud; Jensen, Ingvild Julie Thue; Monakhov, Eduard & Galeckas, Augustinas (2019). Surface effects and optical properties of self-assembled nanostructured a-Si:Al. Nanomaterials. 9(8), s. 1–12. doi: 10.3390/nano9081106. Fulltekst i vitenarkiv Vis sammendrag

  We present a study of the surface effects and optical properties of the self-assembled nanostructures comprised of vertically aligned 5 nm-diameter Al nanowires embedded in an amorphous Si matrix (a-Si:Al). The controlled (partial) removal of Al nanowires in a selective etching process yielded nanoporous a-Si media with a variable effective surface area. Different spectroscopy techniques, such as X-ray photoelectron spectroscopy (XPS), UV-Vis spectrophotometry and photoluminescence (PL), have been combined to investigate the impact of such nanostructuring on optical absorption and emission properties. We also examine long-term exposure to air ambient and show that increasing level of surface oxidation determines the oxide defect-related nature of the dominant PL emission from the nanoporous structures. The role of bulk, nanosize and surface effects in optical properties has been separated and quantified, providing a better understanding of the potential of such nanoporous a-Si:Al structures for future device developments

• Rauwel, Protima; Galeckas, Augustinas; Ducroquet, Frédérique & Rauwel, Erwan (2019). Selective photocurrent generation in HfO2 and carbon nanotube hybrid nanocomposites under Ultra-Violet and visible photoexcitations. Materials Letters. ISSN 0167-577X. 246, s. 45–48. doi: 10.1016/j.matlet.2019.03.030. Fulltekst i vitenarkiv
• Bathen, Marianne Etzelmüller; Galeckas, Augustinas; Müting, Johanna; Ayedh, Hussein Mohammed Hussein; Grossner, Ulrike & Coutinho, José [Vis alle 8 forfattere av denne artikkelen] (2019). Electrical charge state identification and control for the silicon vacancy in 4H-SiC. npj Quantum Information. 5(1), s. 1–9. doi: 10.1038/s41534-019-0227-y. Fulltekst i vitenarkiv Vis sammendrag

  Reliable single-photon emission is crucial for realizing efficient spin-photon entanglement and scalable quantum information systems. The silicon vacancy (VSi) in 4H-SiC is a promising single-photon emitter exhibiting millisecond spin coherence times, but suffers from low photon counts, and only one charge state retains the desired spin and optical properties. Here, we demonstrate that emission from VSi defect ensembles can be enhanced by an order of magnitude via fabrication of Schottky barrier diodes, and sequentially modulated by almost 50% via application of external bias. Furthermore, we identify charge state transitions of VSi by correlating optical and electrical measurements, and realize selective population of the bright state. Finally, we reveal a pronounced Stark shift of 55 GHz for the V1′ emission line state of VSi at larger electric fields, providing a means to modify the single-photon emission. The approach presented herein paves the way towards obtaining complete control of, and drastically enhanced emission from, VSi defect ensembles in 4H-SiC highly suitable for quantum applications.

• Ayedh, Hussein Mohammed Hussein; Grigorev, Aleksei; Galeckas, Augustinas; Svensson, Bengt Gunnar & Monakhov, Eduard (2019). Annealing Kinetics of the Interstitial Carbon–Dioxygen Complex in Silicon. Physica Status Solidi (a) applications and materials science. ISSN 1862-6300. 216(14), s. 1–5. doi: 10.1002/pssa.201800986. Fulltekst i vitenarkiv
• Rauwel, P; Galeckas, Augustinas & Rauwel, Erwan (2019). Time evolution of ZnO-CNT photoluminescence under variable ambient and temperature conditions. IOP Conference Series: Materials Science and Engineering. ISSN 1757-8981. 613(1). doi: 10.1088/1757-899X/613/1/012031. Fulltekst i vitenarkiv Vis sammendrag

  ZnO-CNT hybrid materials were prepared by non-aqueous sol-gel routes at 240ºC. The morphology and defects have been studied by transmission electron microscopy and photoluminescence spectroscopy. The hybrid nanostructures manifest a broad luminescence emission covering the visible spectrum. Variations in photoluminescence with time are observed for the ZnO-CNT hybrid structures exposed to different ambient and temperatures. The studies show that photoluminescence from adsorbed oxygen dominates the emission emanating from other intrinsic defects and also affects the stability of the latter over time.

• Olsen, Vegard Skiftestad; Baldissera, Gustavo; Zimmermann, Christian; Granerød, Cecilie Skjold; Bazioti, Kalliopi & Galeckas, Augustinas [Vis alle 11 forfattere av denne artikkelen] (2019). Evidence of defect band mechanism responsible for band gap evolution in (ZnO)1−x(GaN)x alloys. Physical review B (PRB). ISSN 2469-9950. 100(16). doi: 10.1103/PhysRevB.100.165201. Fulltekst i vitenarkiv Vis sammendrag

  It is known that (ZnO)1−x(GaN)x alloys demonstrate remarkable energy band bowing, making the material absorb in the visible range, in spite of the binary components being classical wide band gap semiconductors. However, the origin of this bowing is not settled; two major mechanisms are under debate: Influence of the orbital repulsion and/or formation of a defect band. In the present work, we applied a combination of the absorption and emission measurements on the samples exhibiting an outstanding nanoscale level of (ZnO)1−x(GaN)x homogeneity as monitored by the high resolution electron microscopy equipped with the energy dispersive x-ray analysis and the electron energy loss spectroscopy; moreover the experimental data were set in the context of the computational analysis of the alloys employing density functional theory and quasiparticle GW approximation. A prominent discrepancy in the band gap values as deduced from the absorption and emission experiments was observed systematically for the alloys with different compositions and interpreted as evidence for the absorption gap shrinking due to the defect band formation. Computational data support the argument, revealing only minor variations in the bulk of the conduction and valence band structures of the alloys, except for a characteristic “tail” in the vicinity of the valence band maximum. As such, we conclude that the energy gap bowing in (ZnO)1−x(GaN)x alloys is due to the defect band formation, presumably at the top of the valence band maximum.

• Montero, José; Galeckas, Augustinas & Karazhanov, Smagul (2018). Photoluminescence Properties of Photochromic Yttrium Hydride Films Containing Oxygen. Physica status solidi (b). ISSN 0370-1972. 255(8). doi: 10.1002/pssb.201800139. Fulltekst i vitenarkiv
• Carvalho, Patricia Almeida; Thøgersen, Annett; Ma, Quanbao; Wright, Daniel Nilsen; Diplas, Spyridon & Galeckas, Augustinas [Vis alle 12 forfattere av denne artikkelen] (2018). Boron-doping of cubic SiC for intermediate band solar cells: a scanning transmission electron microscopy study. SciPost Physics. 5(3). doi: 10.21468/SciPostPhys.5.3.021. Fulltekst i vitenarkiv
• Granerød, Cecilie Skjold; Galeckas, Augustinas; Johansen, Klaus Magnus H; Vines, Lasse & Prytz, Øystein (2018). The temperature-dependency of the optical band gap of ZnO measured by electron energy-loss spectroscopy in a scanning transmission electron microscope. Journal of Applied Physics. ISSN 0021-8979. 123(14), s. 1–6. doi: 10.1063/1.5023316. Fulltekst i vitenarkiv Vis sammendrag

  The optical band gap of ZnO has been measured as a function of temperature using Electron Energy-Loss Spectroscopy (EELS) in a (Scanning) Transmission Electron Microscope ((S)TEM) from approximately 100 K up towards 1000 K. The band gap narrowing shows a close to linear dependency for temperatures above 250 K and is accurately described by Varshni, Bose-Einstein, Pässler and Manoogian-Woolley models. Additionally, the measured band gap is compared with both optical absorption measurements and photoluminescence data. STEM-EELS is here shown to be a viable technique to measure optical band gaps at elevated temperatures, with an available temperature range up to 1500 K and the benefit of superior spatial resolution. © 2018 AIP Publishing

• Galeckas, Augustinas; Carvalho, Patricia Almeida; Ma, Quanbao; Azarov, Alexander; Hovden, Sigurd Slettemark & Thøgersen, Annett [Vis alle 13 forfattere av denne artikkelen] (2018). Optical and microstructural investigation of heavy B-doping effects in sublimation-grown 3C-SiC. Materials Science Forum. ISSN 0255-5476. 924, s. 221–224. doi: 10.4028/www.scientific.net/MSF.924.221. Fulltekst i vitenarkiv Vis sammendrag

  In this work, a complementary microstructural and optical approach is used to define processing conditions favorable for the formation of deep boron-related acceptor centers that may provide a pathway for achieving an intermediate band behavior in highly B-doped 3C-SiC. The crystallinity, boron solubility and precipitation mechanisms in sublimation-grown 3C-SiC crystals implanted to 1-3 at.% B concentrations were investigated by STEM. The revealed defect formation and boron precipitation trends upon thermal treatment in the range 1100-2000°C have been cross-correlated with the optical characterization results provided by imaging PL spectroscopy. We discuss optical activity of the implanted B ions in terms of both shallow acceptors and deep D-centers, a complex formed by a boron atom and a carbon vacancy, and associate the observed spectral developments upon annealing with the strong temperature dependence of the D-center formation efficiency, which is further enhanced by the presence of implantation-induced defects.

• Bergum, Kristin; Riise, Heine Nygard; Gorantla, Sandeep Madhukar; Lindberg, Per; Jensen, Ingvild Julie Thue & Gunnæs, Anette Eleonora [Vis alle 10 forfattere av denne artikkelen] (2018). Improving carrier transport in Cu2O thin films by rapid thermal annealing. Journal of Physics: Condensed Matter. ISSN 0953-8984. 30(7). doi: 10.1088/1361-648X/aaa5f4. Fulltekst i vitenarkiv
• Ayedh, Hussein Mohammed Hussein; Bathen, Marianne Etzelmüller; Galeckas, Augustinas; Hassan, Jawad U; Bergman, J. P. & Nipoti, Roberta [Vis alle 8 forfattere av denne artikkelen] (2018). Controlling the carbon vacancy in 4H-SiC by thermal processing. ECS Transactions. ISSN 1938-5862. 86(12), s. 91–97. doi: 10.1149/08612.0091ecst. Fulltekst i vitenarkiv
• Venkatachalapathy, Vishnukanthan; Galeckas, Augustinas; Azarov, Alexander; Vines, Lasse & Kuznetsov, Andrej (2018). Phase stability and strain accumulation in CdO as a function of Cd/O supply during MOVPE synthesis. Superlattices and Microstructures. ISSN 0749-6036. 120, s. 569–577. doi: 10.1016/j.spmi.2018.06.017. Fulltekst i vitenarkiv
• Ma, Quanbao; Carvalho, Patricia; Galeckas, Augustinas; Azarov, Alexander; Hovden, Sigurd Slettemark & Thøgersen, Annett [Vis alle 13 forfattere av denne artikkelen] (2017). Characterization of B-implanted 3C-SiC for intermediate band solar cells. Materials Science Forum. ISSN 0255-5476. 897, s. 299–302. doi: 10.4028/www.scientific.net/MSF.897.299. Fulltekst i vitenarkiv Vis sammendrag

  Sublimation-grown 3C-SiC crystals were implanted with B ions at elevated temperature (400 °C) using multiple energies (100 to 575 keV) with a total dose of 1.3×1017 atoms/cm2 in order to form intermediate band (IB) in 3C-SiC. The samples were then annealed at 1400 °C for 60 min. An anomalous area in the center was observed in the PL emission pattern. The SIMS analysis indicated that the B concentration was the same both within and outside the anomalous area. The buried boron box-like concentration profile can reach ~3×1021 cm-3 in the plateau region. In the anomalous area a broad emission band (possible IB) emerges at around ~1.7-1.8 eV, which may be associated with B-precipitates having a sufficiently high density. Sublimation-grown 3C-SiC crystals were implanted with B ions at elevated temperature (400 °C) using multiple energies (100 to 575 keV) with a total dose of 1.3×1017 atoms/cm2 in order to form intermediate band (IB) in 3C-SiC. The samples were then annealed at 1400 °C for 60 min. An anomalous area in the center was observed in the PL emission pattern. The SIMS analysis indicated that the B concentration was the same both within and outside the anomalous area. The buried boron box-like concentration profile can reach ~3×1021 cm-3 in the plateau region. In the anomalous area a broad emission band (possible IB) emerges at around ~1.7-1.8 eV, which may be associated with B-precipitates having a sufficiently high density.

• Kjeldstad, Torunn; Thøgersen, Annett; Nilsen, Ola; Monakhov, Edouard & Galeckas, Augustinas (2017). Controllable template approach for ZnO nanowire growth. Physica Status Solidi (a) applications and materials science. ISSN 1862-6300. 214(2), s. 1–6. doi: 10.1002/pssa.201600480. Fulltekst i vitenarkiv Vis sammendrag

  Anodic aluminum oxide (AAO) is an optically transparent material with uniform hexagonal pores, which has widely been used as a template for nanowire growth. This study examines the potential of utilizing commercially available AAO to fabricate sub-10 nm ZnO nanowires by atomic layer deposition. The pore diameter of the AAO framework is reduced by controlled deposition of . Subsequently, ZnO is deposited and ZnO nanowires are obtained. The analysis of structural and optical properties shows that the nanowires are polycrystalline, and exhibit a pronounced near band edge emission. Photoluminescence (PL) measurements are performed to monitor the effect of additional coating with and ZnO, on the optical stability of the AAO. The measurements indicate that the PL is highly influenced by the adsorption and desorption of species from the ambient at the surface. ALD deposition of a thin layer reduces considerably the effect of ambient atmosphere. The layer of facilitates PL characterization of very thin ZnO nanowires.

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• Azarov, Alexander; Slusar, Tetiana; Galeckas, Augustinas; Moon, Kiwon; Hallen, Anders & Kuznetsov, Andrej (2024). Dynamic defect annealing in Er implanted LiNbO3. Fulltekst i vitenarkiv
• Azarov, Alexander; Galeckas, Augustinas; Cora, Ildikó; Fogarassy, Zsolt; Venkatachalapathy, Vishnukanthan & Monakhov, Eduard [Vis alle 7 forfattere av denne artikkelen] (2024). Thermal stability of double-layer gamma/beta Ga2O3 structures fabricated by ion beams. Fulltekst i vitenarkiv
• Hommedal, Ylva Knausgård; Frodason, Ymir Kalmann; Galeckas, Augustinas; Vines, Lasse & Johansen, Klaus Magnus H (2024). Zn diffusion and luminescence from Zn acceptors in Zn doped β-Ga2O3. Fulltekst i vitenarkiv
• Frodason, Ymir Kalmann; Galeckas, Augustinas; Galazka, Zbigniew; Vines, Lasse & Walle, Chris G. Van De (2024). Broad luminescence in single-crystalline ZnGa2O. Fulltekst i vitenarkiv
• Kjeldby, Snorre Braathen; Fernandez, Javier Garcia; Galeckas, Augustinas; Jensen, Ingvild Julie Thue; Prytz, Øystein & Vines, Lasse (2024). Cross-sectional cathodoluminescence measurements in implanted and annealed gallium oxide. Fulltekst i vitenarkiv
• Fernandez, Javier Garcia; Kjeldby, Snorre Braathen; Nguyen, Phuong Dan; Haug, Kristian; Galeckas, Augustinas & Jensen, Ingvild Julie Thue [Vis alle 9 forfattere av denne artikkelen] (2023). Optical properties and structure relationship in ZnO:Fe with inversion domain boundaries and ZnFe2O4/ZnO heterostructures. Fulltekst i vitenarkiv
• Bathen, Marianne Etzelmüller; Johnson, Brett C.; Galeckas, Augustinas; martins, maria m; Kumar, Piyush & Silkinis, Rokas [Vis alle 11 forfattere av denne artikkelen] (2023). Doping-induced color centers in silicon carbide ​. Fulltekst i vitenarkiv
• Fernandez, Javier Garcia; Kjeldby, Snorre Braathen; Nguyen, Phuong Dan; Haug, Kristian; Galeckas, Augustinas & Jensen, Ingvild Julie Thue [Vis alle 9 forfattere av denne artikkelen] (2022). Structural and optical investigation of Fe-ZnO nanoarchitectures: from inversion domain boundaries to ZnO/ZnFe2O4 heterostructure. Fulltekst i vitenarkiv
• Kang, Xiaolan; Reinertsen, Vilde Mari; Both, Kevin Gregor; Galeckas, Augustinas; Aarholt, Thomas & Prytz, Øystein [Vis alle 9 forfattere av denne artikkelen] (2022). Galvanic restructuring of exsolved nanoparticles for plasmonic and electrocatalytic energy conversion. Fulltekst i vitenarkiv
• Kang, Xiaolan; Reinertsen, Vilde Mari; Both, Kevin Gregor; Galeckas, Augustinas; Aarholt, Thomas & Prytz, Øystein [Vis alle 9 forfattere av denne artikkelen] (2022). Galvanic Restructuring of Exsolved Nanoparticles for Plasmonic and Electrocatalytic Energy Conversion (Small 29/2022 Inside back cover feature). 18(29), s. 2270156–2270156. Fulltekst i vitenarkiv
• Kang, Xiaolan; Chaperman, Larissa; Galeckas, Augustinas; Ammar-Merah, Souad; Mammeri, Fayna & Norby, Truls [Vis alle 7 forfattere av denne artikkelen] (2022). Water Vapor Photoelectrolysis in an All Solid-State Photoelectrochemical Cell. Fulltekst i vitenarkiv
• Galeckas, Augustinas; Karsthof, Robert Michael; Gana, Kingsly; Kok, Angela; Bathen, Marianne Etzelmüller & Vines, Lasse [Vis alle 7 forfattere av denne artikkelen] (2022). Cross-sectional carrier lifetime profiling and deep level monitoring in silicon carbide films exhibiting variable carbon vacancy concentrations. Fulltekst i vitenarkiv Vis sammendrag

  We report on the carrier lifetime control over 150 μmthick 4H-SiC epitaxial layers via thermal generation and annihilation of carbon vacancy (VC) related Z1/2lifetime killer sites. The defect developments upon typical SiC processing steps, such as high- and moderate-temperature anneals in the presence of a carbon cap,are monitored by combining electrical characterization techniques capable of VC depth-profiling, capacitance-voltage (CV) and deep-level transient spectroscopy (DLTS), with a novel all-optical approach of cross-sectional carrier lifetime profiling across 4H-SiC epilayer/substrate based on imaging time-resolved photoluminescence (TRPL) spectroscopy in orthogonal pump-probe geometry,which readily exposes in-depth efficacy ofdefect reduction and surface recombination effects.The lifetime control is realized byinitialhigh-temperature treatment (1800ºC) to increase VC concentration to ~1013 cm-3 level followed by a moderate-temperature (1500ºC) post-annealing of variable duration under C-rich thermodynamic equilibrium conditions. The post-annealing carried out for 5 hours in effect eliminates VCthroughout the entire ultra-thick epilayer. The reduction of VC-related Z1/2 sites is proven by a significant lifetime increase from 0.8 μs to 2.5 μs. We discuss the upper limit of lifetimes in terms of carrier surface leakage and presence of other non-radiative recombination centers besides Z1/2, possibly related to residual impurities such as boron.

• Kang, Xiaolan; Reinertsen, Vilde Mari; Both, Kevin Gregor; Galeckas, Augustinas; Aarholt, Thomas & Prytz, Øystein [Vis alle 9 forfattere av denne artikkelen] (2022). Exsolved nanoparticles, galvanically restructured for tunable photo-electrocatalytic energy conversion. Fulltekst i vitenarkiv
• Faraj, Sayed; Bathen, Marianne Etzelmüller; Galeckas, Augustinas; Myrold, Andreas; Stene-Johansen, Ingar & Jørstad, Øystein Kalsnes [Vis alle 7 forfattere av denne artikkelen] (2022). Retinal injuries in seven teenage boys from the same handheld laser. American Journal of Ophthalmology Case Reports. 27. doi: 10.1016/j.ajoc.2022.101596. Fulltekst i vitenarkiv Vis sammendrag

  This paper presents retinal injuries in 10 eyes of seven teenagers who had been playing with a handheld laser. They reported different degrees of visual symptoms in the form of central scotomas. Clinical examination revealed light burns in the maculae and disruption of the retinal layers on OCT. One patient developed secondary choroidal neovascularization (CNV), which was successfully treated with intravitreal ranibizumab. For some of the patients, the injuries led to permanent visual sequela. This devastating case series emphasizes the need for awareness among minors, parents and communities about the danger of playing with handheld lasers.

• Karsthof, Robert Michael; Bathen, Marianne Etzelmüller; Galeckas, Augustinas & Vines, Lasse (2022). Conversion pathways of primary defects by annealing in proton-irradiated n-type 4H-SiC. Fulltekst i vitenarkiv
• Kjeldby, Snorre Braathen; Nguyen, Phuong Dan; Fernandez, Javier Garcia; Haug, Kristian; Galeckas, Augustinas & Jensen, Ingvild Julie Thue [Vis alle 9 forfattere av denne artikkelen] (2022). Optical properties of Fe-decorated inversion domain boundaries and embedded spinel zinc ferrite nanoparticles in zinc oxide. Fulltekst i vitenarkiv
• Bathen, Marianne Etzelmüller; Karsthof, Robert Michael; Kumar, Piyush; Galeckas, Augustinas; Kuznetsov, Andrej & Vines, Lasse [Vis alle 7 forfattere av denne artikkelen] (2022). Impact of C-injection in 4H-SiC on defect distribution and minority carrier lifetime. Fulltekst i vitenarkiv
• Bathen, Marianne Etzelmüller; Karsthof, Robert Michael; Kumar, Piyush; Galeckas, Augustinas; Kuznetsov, Andrej Yu. & Vines, Lasse [Vis alle 7 forfattere av denne artikkelen] (2022). Impact of C-injection in SiC on defect distribution and minority carrier lifetime. Fulltekst i vitenarkiv
• Bathen, Marianne Etzelmüller; Enga, Marius Johan; Selnesaunet, Gard Momrak; Kjeldby, Snorre Braathen; Galeckas, Augustinas & Müting, Johanna [Vis alle 8 forfattere av denne artikkelen] (2022). Charge state control over point defects in SiC devices. Fulltekst i vitenarkiv
• Kjeldby, Snorre Braathen; Nguyen, Phuong Dan; Haug, Kristian; Galeckas, Augustinas; Jensen, Ingvild Julie Thue & Thøgersen, Annett [Vis alle 8 forfattere av denne artikkelen] (2021). EELS and SEM-CL investigations of ZnFe2O4 nanoparticles and iron-decorated inversion domain boundaries in bulk ZnO. Fulltekst i vitenarkiv
• Bathen, Marianne Etzelmüller; Karsthof, Robert Michael; Linnarsson, Margareta; Galeckas, Augustinas; Kuznetsov, Andrej & Grossner, Ulrike [Vis alle 7 forfattere av denne artikkelen] (2021). Stability, evolution and diffusion of intrinsic point defects in 4H-SiC. Fulltekst i vitenarkiv
• Karsthof, Robert Michael; Bathen, Marianne Etzelmüller; Galeckas, Augustinas; Enga, Marius & Vines, Lasse (2021). Conversion pathways of primary defects by annealing in proton-irradiated n-type 4H-SiC. Fulltekst i vitenarkiv
• Karsthof, Robert Michael; Bathen, Marianne Etzelmüller; Galeckas, Augustinas & Vines, Lasse (2021). Conversion pathways of primary defects by annealing in proton-irradiated n-type 4H-SiC. Fulltekst i vitenarkiv
• Bathen, Marianne Etzelmüller; Galeckas, Augustinas; Müting, Johanna; Ayedh, Hussein Mohammed Hussein; Grossner, Ulrike & Coutinho, J [Vis alle 7 forfattere av denne artikkelen] (2019). Electrical enhancement and switching of single-photon emission from the silicon vacancy in 4H-SiC. Fulltekst i vitenarkiv
• Frodason, Ymir Kalmann; Johansen, Klaus Magnus H; Galeckas, Augustinas & Vines, Lasse (2019). Optical properties of donor-complexed Li_Zn in ZnO. Fulltekst i vitenarkiv
• Azarov, Alexander; Galeckas, Augustinas; Mieszczyński, Cyprian; Hallen, Anders & Kuznetsov, Andrej (2019). Effects of annealing on photoluminescence and defect interplay in ZnO bombarded with heavy ions: crucial role of the ion dose. Fulltekst i vitenarkiv
• Vasquez, Geraldo Cristian; Galeckas, Augustinas; Johansen, Klaus Magnus H; Vines, Lasse & Svensson, Bengt Gunnar (2019). Optical and electrical properties of single ion-tracks in crystalline SiC. Fulltekst i vitenarkiv
• Vasquez, Geraldo Cristian; Bazioti, Kalliopi; Galeckas, Augustinas; Johansen, Klaus Magnus H; Granerød, Cecilie Skjold & Nguyen, Phuong Dan [Vis alle 8 forfattere av denne artikkelen] (2019). Luminescent properties of Zn2GeO4 nanoparticles embedded in ZnO. Fulltekst i vitenarkiv
• Bathen, Marianne Etzelmüller; Galeckas, Augustinas; Müting, Johanna; Ayedh, Hussein Mohammed Hussein; Grossner, Ulrike & Coutinho, José [Vis alle 7 forfattere av denne artikkelen] (2019). Electrical enhancement and switching of single-photon emission from the silicon vacancy in 4H-Si. Fulltekst i vitenarkiv Vis sammendrag

  The high-spin ground state and bright single-photon emission of the silicon vacancy (VSi) in 4H-SiC offer exciting possibilities for quantum technology and spintronics applications, especially as both are available at room temperature [1,2]. However, quantum compatibility only exists for the singly negative VSi, and single-photon counts are still too low to realize efficient spin-photon interfaces without resorting to complex nanofabrication methods [3]. Herein, we demonstrate enhanced optical emission from VSi using Schottky barrier diode (SBD) formation, and attribute our findings to increased occupancies of VSi-1.

• Bathen, Marianne Etzelmüller; Galeckas, Augustinas; Müting, Johanna; Ayedh, Hussein Mohammed Hussein; Grossner, Ulrike & Coutinho, José [Vis alle 8 forfattere av denne artikkelen] (2019). Electrical charge-state identification and emission intensity modulation of the silicon vacancy in 4H-SiC. Fulltekst i vitenarkiv
• Bathen, Marianne Etzelmüller; Galeckas, Augustinas; Frodason, Ymir Kalmann; Vines, Lasse & Svensson, Bengt Gunnar (2018). Tuning silicon vacancy formation in 4H-SiC via proton irradiation for quantum technology. Fulltekst i vitenarkiv
• Vasquez, Geraldo Cristian; Johansen, Klaus Magnus H; Galeckas, Augustinas; Vines, Lasse; Svensson, Bengt Gunnar & Maestre, David (2018). Single ion-tracks in crystalline ZnO and their influence on the near band edge luminescence. Fulltekst i vitenarkiv
• Bathen, Marianne Etzelmüller; Vines, Lasse; Galeckas, Augustinas; Frodason, Ymir Kalmann & Svensson, Bengt Gunnar (2018). Charge state transitions of the silicon vacancy in 4H-SiC: Combined DLTS, PL and DFT study. Fulltekst i vitenarkiv
• Bathen, Marianne Etzelmüller; Vines, Lasse; Galeckas, Augustinas; Frodason, Ymir Kalmann & Svensson, Bengt Gunnar (2018). Correlating charge state transitions of the Si vacancy to the S1/S2 peaks in DLTS spectra of n-type 4H-SiC. Fulltekst i vitenarkiv
• Ayedh, Hussein Mohammed Hussein; Bathen, Marianne Etzelmüller; Galeckas, Augustinas; Hassan, Jawad Ul; Bergman, J. P. & Nipoti, Roberta [Vis alle 8 forfattere av denne artikkelen] (2018). Controlling the Carbon Vacancy in 4H-SiC By Thermal Processing. Fulltekst i vitenarkiv
• Venkatachalapathy, Vishnukanthan; Vajeeston, Ponniah; Galeckas, Augustinas; Vines, Lasse & Kuznetsov, Andrej (2018). Direct and indirect bandgaps of Cadmium Oxide. Fulltekst i vitenarkiv
• Thøgersen, Annett; Stange, Marit Synnøve Sæverud; Galeckas, Augustinas; Nilsen, Ola & Monakhov, Eduard (2018). Aluminum nanowires in amorphous silicon. Fulltekst i vitenarkiv
• Kjeldstad, Torunn; Thøgersen, Annett; Galeckas, Augustinas; Monakhov, Eduard; Stange, Marit Synnøve Sæverud & Nilsen, Ola (2018). Aluminum nanowires in amorphous silicon. Fulltekst i vitenarkiv
• Ayedh, Hussein Mohammed Hussein; Azarov, Alexander; Galeckas, Augustinas; Svensson, Bengt Gunnar & Monakhov, Edouard (2017). DLTS study of the interstitial carbon–oxygen complex in proton irradiated p-type Si. Fulltekst i vitenarkiv
• Thøgersen, Annett; Kjeldstad, Torunn; Jensen, Ingvild Julie Thue; Muntingh, Agnar Georg Peder; Stange, Marit Synnøve Sæverud & Ulyashin, Alexander [Vis alle 9 forfattere av denne artikkelen] (2017). Plasmonic properties of aluminium nanowires in amorphous silicon and inverted silicon nanowires. Fulltekst i vitenarkiv
• Thøgersen, Annett; Kjeldstad, Torunn; Jensen, Ingvild Julie Thue; Stange, Marit Synnøve Sæverud; Ulyashin, Alexander & Galeckas, Augustinas [Vis alle 9 forfattere av denne artikkelen] (2017). Growing and characterizing self-organizing aluminium nanowires in amorphous silicon. Fulltekst i vitenarkiv
• Granerød, Cecilie Skjold; Galeckas, Augustinas; Vines, Lasse; Johansen, Klaus Magnus H & Prytz, Øystein (2017). Temperature-dependency of the ZnO band gap measured by STEM-EELS. Fulltekst i vitenarkiv
• Nyborg, Martin; Lindberg, Per; Svensson, Bengt Gunnar; Monakhov, Edouard & Galeckas, Augustinas (2017). DC Magnetron Sputter Deposition of CuxO Thin Films The Effect of Target Power and O2 Flow. Fulltekst i vitenarkiv Vis sammendrag

  In this study, we report on the effect of target power and O2 flow on DC magnetron sputter deposited CuxO thin films. Target power (Ptar) and oxygen flow (QO2) have been varied in the 80 - 100 W and 12-19 sccm range while keeping all other parameters constant.

• Frodason, Ymir Kalmann; Bergum, Kristin; Sky, Thomas Neset; Ingebrigtsen, Mads Eide; Borgersen, Jon & Ellingsen, Josef Gert Åsheim [Vis alle 8 forfattere av denne artikkelen] (2017). MiNa-Lab tour highlighting LENS activities. Fulltekst i vitenarkiv

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