Lasse Vines

• Thøgersen, Annett; Muntingh, Agnar Georg Peder; Vines, Lasse; Prytz, Øystein; Kneiß, Max & Grundmann, Marius [Vis alle 8 forfattere av denne artikkelen] (2026). Decoupling composition and band gap in κ-Ga<inf>2</inf>O<inf>3</inf>heterostructures via STEM-EELS. Ultramicroscopy. ISSN 0304-3991. 286. doi: 10.1016/j.ultramic.2026.114417. Fulltekst i vitenarkiv
• Strandbakke, Ragnar; Wachowski, Sebastian Lech; Balaguer, Maria; Vines, Lasse; Sky, Thomas Neset & Szpunar, Iga [Vis alle 12 forfattere av denne artikkelen] (2026). Governing principles of hydration of mixed proton conducting Co-based double perovskites. Nature Communications. 17, s. 1–10. doi: 10.1038/s41467-026-70212-w. Fulltekst i vitenarkiv Vis sammendrag

  Proton ceramic electrochemical cells PCECs hold promise for efficient, sustainable production and use of hydrogen. The positive electrodes are mixed proton conducting perovskites that facilitate water splitting and oxygen reduction, but the factors that determine the protonation are poorly under stood. Here, we establish the governing principles of protonation through a study of hydration of 45 double perovskites with the general formula AIAIICo2O6 δ, having Ba or Ba+Sr on AI and a mix of rare earths (Y and lanthanides Ln =La,Pr,Nd,Sm,Gd,Dy,Tb,Lu)onAII. We show how hydration is coupled to the A-site basicity and disorder as well as population of electron holes in the Co-O bond (Co oxidation state), promoted by a closed or semiclosed Ln 4f shell, i.e., Ln =La,Gd,Lu.

• 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.

• Ousdal, Erlend Lemva; Ghezellou, Misagh; Ul-Hassan, Jawad; Kuznetsov, Andrej; Vines, Lasse & Bathen, Marianne Etzelmüller (2025). Identification of electrically active defects in 6⁢𝐻-SiC. PHYSICAL REVIEW MATERIALS. 9(12). doi: 10.1103/qzfw-162p. Fulltekst i vitenarkiv Vis sammendrag

  Deep level defects in silicon carbide (SiC) are of great importance for developing both power electronics and quantum technology applications based on SiC material. While the more technologically mature 4⁢𝐻 polytype has been widely explored, electrical identification of deep level defect states in 6⁢𝐻 -SiC has not been completed. This work aims to identify irradiation-induced charge state transition levels arising from intrinsic defects in 6⁢𝐻 -SiC using deep level transient spectroscopy (DLTS) and the formation energy diagram formalism based on density functional theory (DFT) calculations. By comparing experimental results of 6⁢𝐻 -SiC epitaxial layers with measurements of 4⁢𝐻 -SiC material that has been grown under identical conditions, combined with DFT calculations, we assign possible origins for the observed DLTS-signatures.

• Langørgen, Amanda; Frodason, Ymir Kalmann; Jensen, Ingvild Julie Thue; Turiansky, Mark E.; Walle, Chris G. Van de & Vines, Lasse (2025). Formation of the E4* level in implanted β-Ga2O3. PHYSICAL REVIEW MATERIALS. 9. doi: 10.1103/3ktr-6kmw. Fulltekst i vitenarkiv
• Kjeldby, Snorre Braathen; Nielsen, Dina Marie; Cooil, Simon Phillip; Frodason, Ymir Kalmann; Zacharaki, Eirini & Lee, In Hwan [Vis alle 10 forfattere av denne artikkelen] (2025). Tuning Properties of II-IV-Nitrides for Optoelectronic Applications. Advanced Optical Materials. 13(36). doi: 10.1002/adom.202502634. Fulltekst i vitenarkiv Vis sammendrag

  The earth-abundant II-IV-nitrides ZnSnN2 and ZnGeN2 are direct bandgap semiconductors with a wurtzite-derived crystal structure. Their alloys, ZnSnxGe1 − xN2, have bandgaps tunable across the full visible spectrum, making them interesting for many optoelectronic applications. Here, electrical, structural, and optical properties of near-stoichiometric ZnSnxGe1 − xN2 alloys, i.e., where [Zn]/([Zn]+[Ge]+[Sn]) ≈ 0.5, are reported, for samples synthesized by reactive magnetron sputtering. These results reveal unprecedentedly high electrical mobilities in Ge-rich alloys, with values of 136 and 400 cm2/Vs at room-temperature and ≈100 K, respectively. The bandgaps are determined from optical absorption measurements combined with hybrid density functional calculations and reveal a significant Burstein–Moss shift in the Sn rich alloys. Finally, band alignments are determined in the sputter-grown thin films by combining optical transmission measurements, hybrid density functional calculations, and UV photoelectron spectroscopy measurements, where the bandgap variation is predominantly caused by a shift of the conduction band edge. This work elucidates in unprecedented detail the tuning of optical and electrical properties in ZnSnxGe1 − xN2 by variation of the chemical composition, where bandgap values of alloys with x ∈ [0.5−0.7] are suitable for top cell absorbers in two-terminal tandem solar cells assuming a Si bottom cell.

• Fernandez, Javier Garcia; Kjeldby, Snorre Braathen; Zeng, L. J.; Olsson, E.; Vines, Lasse & Prytz, Øystein (2025). Formation and stability of Ge nanocrystals in polymorph converted Ga2O3: Temperature-driven journey. Applied Physics Letters. ISSN 0003-6951. 126(5). doi: 10.1063/5.0235371. Fulltekst i vitenarkiv Vis sammendrag

  The influence of germanium (Ge) implantation on β-Ga2O3 followed by ex situ annealing through polymorph conversion in air at various temperatures (600–1100 °C) is studied. Atomic resolution aberration-corrected scanning transmission electron microscopy is employed to examine the structural and microstructural changes induced by the annealing process. The results show that the thermal annealing process leads to the formation of Ge nanocrystals, which subsequently disappear, leaving nano-voids inside the Ge-doped Ga2O3 matrix. In addition, the microstructure displays distinct crystallographic relationships in annealed β-Ga2O3 forming layers with well-defined interfaces. This work reveals the unique effects of Ge-implantation, demonstrating the possible functionalization of Ga2O3 with Ge nanocrystals.

• Samperi, Orazio; Azarov, Alexander; Bobal, Viktor; Bertolini, Mario Pietro; Cantiano, Massimiliano & Vines, Lasse [Vis alle 9 forfattere av denne artikkelen] (2025). Effects of ion channelling on 350 keV proton implantation of 4H-SiC measured by D-SIMS and DLTS defect profiling. Materials Science in Semiconductor Processing. ISSN 1369-8001. 190. doi: 10.1016/j.mssp.2025.109320. Fulltekst i vitenarkiv
• Silkinis, Rokas; Maciaszek, Marek; Žalandauskas, Vytautas; Bathen, Marianne Etzelmüller; Vines, Lasse & Alkauskas, Audrius [Vis alle 7 forfattere av denne artikkelen] (2025). Optical lineshapes of the C center in silicon from ab initio calculations: Interplay of localized modes and bulk phonons. Physical review B (PRB). ISSN 2469-9950. 111(12). doi: 10.1103/PhysRevB.111.125136. Fulltekst i vitenarkiv
• Herklotz, F.; Chaplygin, I.; Lavrov, E.V.; Melnikov, V.V.; Galazka, Z. & Vines, Lasse (2025). Transition metal-hydrogen complexes in SnO2. Physical review B (PRB). ISSN 2469-9950. 111(19). doi: 10.1103/PhysRevB.111.195208. Fulltekst i vitenarkiv
• Ghezellou, Misagh; Ousdal, Erlend Lemva; Bathen, Marianne Etzelmüller; Vines, Lasse & Ul-Hassan, Jawad (2025). Influence of different hydrocarbons on impurities and minority carrier lifetime in 4H-SiC epitaxial layers. JPhys Materials. 8, s. 1–12. doi: 10.1088/2515-7639/adb7c0. Fulltekst i vitenarkiv Vis sammendrag

  This study explores the influence of different hydrocarbons, methane and propane, on the properties of 4H-SiC epitaxial layers grown by chloride-based chemical vapor deposition. By systematically varying the C/Si and N/C ratios during epitaxial growth, and employing a comprehensive suite of characterization techniques, a better understanding of how growth conditions influence material properties is gained. We show that the n-type dopant incorporation strongly depends on the choice of hydrocarbon especially at lower doping levels. Furthermore, we have observed that methane contributes to a relatively longer carrier lifetime value compared to propane, though a similar lifetime limiting carbon vacancy defect concentration has been observed for both hydrocarbons in as-grown epitaxial layers. Moreover, additional defect levels are also suggested by deep-level transient spectroscopy, potentially related to chlorine complexes, with varying concentrations depending on the choice of hydrocarbon and C/Si ratio. These observations offer insights into the complicated interplay of factors influencing doping, minority carrier lifetime, and defect formation in 4H-SiC epitaxial layers during the epitaxial growth process, and contribute to the optimization of growth parameters depending on the application in question.

• Houam, Sirine; Ouaddah, Hadjer; Regula, Gabrielle; Périchaud, Isabelle; Reinhart, Guillaume & Sabatino, Marisa Di [Vis alle 12 forfattere av denne artikkelen] (2025). A method to relate the presence of structural defects and impurities and their impact on the electrical activity in silicon for photovoltaic applications. Solar Energy Materials and Solar Cells. ISSN 0927-0248. 282. doi: 10.1016/j.solmat.2025.113415. Fulltekst i vitenarkiv
• Hommedal, Ylva Knausgård; Bathen, Marianne Etzelmüller; Reinertsen, Vilde Mari; Johansen, Klaus Magnus H; Vines, Lasse & Frodason, Ymir Kalmann (2024). Theoretical modeling of defect diffusion in wide bandgap semiconductors. Journal of Applied Physics. ISSN 0021-8979. 135. doi: 10.1063/5.0205866. Fulltekst i vitenarkiv Vis sammendrag

  Since the 1940s, it has been known that diffusion in crystalline solids occurs due to lattice defects. The diffusion of defects can have a great impact on the processing and heat treatment of materials as the microstructural changes caused by diffusion can influence the material qualities and properties. It is, therefore, vital to be able to control the diffusion. This implies that we need a deep understanding of the interactions between impurities, matrix atoms, and intrinsic defects. The role of density functional theory (DFT) calculations in solid-state diffusion studies has become considerable. The main parameters to obtain in defect diffusion studies with DFT are formation energies, binding energies, and migration barriers. In particular, the utilization of the nudged elastic band and the dimer methods has improved the accuracy of these parameters. In systematic diffusion studies, the combination of experimentally obtained results and theoretical predictions can reveal information about the atomic diffusion processes. The combination of the theoretical predictions and the experimental results gives a unique opportunity to compare parameters found from the different methods and gain knowledge about atomic migration. In this Perspective paper, we present case studies on defect diffusion in wide bandgap semiconductors. The case studies cover examples from the three diffusion models: free diffusion, trap-limited diffusion, and reaction diffusion. We focus on the role of DFT in these studies combined with results obtained with the experimental techniques secondary ion mass spectrometry and deep-level transient spectroscopy combined with diffusion simulations.

• Bathen, Marianne Etzelmüller; Kumar, Piyush; Ghezellou, Misagh; Belanche, Manuel; Vines, Lasse & Ul-Hassan, Jawad [Vis alle 7 forfattere av denne artikkelen] (2024). Dual configuration of shallow acceptor levels in 4H-SiC. Materials Science in Semiconductor Processing. ISSN 1369-8001. 177. doi: 10.1016/j.mssp.2024.108360. Fulltekst i vitenarkiv Vis sammendrag

  Acceptor dopants in 4H-SiC exhibit energy levels that are located deeper in the band gap than the thermal energy at room temperature (RT), resulting in incomplete ionization at RT. Therefore, a comprehensive understanding of the defect energetics and how the impurities are introduced into the material is imperative. Herein, we study impurity related defect levels in 4H-SiC epitaxial layers (epi-layers) grown by chemical vapor deposition (CVD) under various conditions using minority carrier transient spectroscopy (MCTS). We find two trap levels assigned to boron impurities, B and D, which are introduced to varying degrees depending on the growth conditions. A second acceptor level that was labeled X in the literature and attributed to impurity related defects is also observed. Importantly, both the B and X levels exhibit fine structure revealed by MCTS measurements. We attribute the fine structure to acceptor impurities at hexagonal and pseudo-cubic lattice sites in 4H-SiC, and tentatively assign the X peak to Al based on experimental findings and density functional theory calculations.

• Samperi, Orazio; Vines, Lasse; Bertolini, Mario Pietro; Cantiano, Massimiliano; Coffa, Salvo & Fragalà, Maria Elena (2024). Hydrogen depth profiling and multi-energy proton implantation: SIMS as a tool for implant process control. Materials Science in Semiconductor Processing. ISSN 1369-8001. 174. doi: 10.1016/j.mssp.2024.108219. Fulltekst i vitenarkiv
• 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
• Fernandez, Javier Garcia; Kjeldby, Snorre Braathen; Zeng, L. J.; Azarov, Alexander; Pokle, Anuj & Nguyen, Phuong Dan [Vis alle 10 forfattere av denne artikkelen] (2024). In situ atomic-resolution study of transformations in double polymorph γ/β-Ga2O3 structures. Materials Advances. 5, s. 3824–3831. doi: 10.1039/D3MA01011B. Fulltekst i vitenarkiv Vis sammendrag

  Disorder-induced formation of metastable Ga2O3 polymorphs as well as the recovery of the stable state upon annealing attract attention because of the fundamental novelty and rapidly increasing interest in the use of Ga2O3 in practical applications. In this study, double polymorph γ/β-Ga2O3 structures fabricated by the radiation-induced disorder approach were used as a starting point for systematic in situ annealing electron microscopy experiments. We show that, under the conditions of the TEM in situ annealing, double γ/β-Ga2O3 polymorph structures remained stable up to 300 °C, when onsets of the γ-to-β transformation become traceable, leading to a prominent γ- and β-mixture already at 500 °C. Interestingly, the recrystallization of the β-Ga2O3 occurs throughout the whole γ-film and the preferential alignments at the newly emerging γ/β-interfaces are different from that of the initial γ/β-interface formed as a result of the disorder-induced ordering. The alignments of the two polymorphs are maintained as a function of temperature – with a reduction in the volumetric ratio of γ-domains for increasing annealing temperature. Finally, at 1100 °C, γ-Ga2O3 fully transforms into β-Ga2O3, without dominating crystallographic relationships or preferred orientations, indicating that energy barriers are not any longer implied limiting factors, because of a sufficiently high thermal energy supply. Thus, these TEM in situ measurements enable a new level of accuracy for assessing polymorphic transformations in Ga2O3.

• 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.

• Samperi, Orazio; Vines, Lasse; Bertolini, Mario Pietro; Cantiano, Massimiliano; Coffa, Salvo & Fragalà, Maria Elena (2024). Hydrogen depth profiling and multi-energy proton implantation: SIMS as a tool for implant process control. Materials Science in Semiconductor Processing. ISSN 1369-8001. doi: 10.1016/j.mssp.2024.108219. Fulltekst i vitenarkiv
• Hommedal, Ylva Knausgård; Frodason, Ymir Kalmann; Vines, Lasse & Johansen, Klaus Magnus H (2024). Diffusion of Ge Donors in β-Ga2O3. Physica status solidi (b). ISSN 0370-1972. doi: 10.1002/pssb.202400355. Fulltekst i vitenarkiv Vis sammendrag

  Diffusion of Ge donors in β-Ga2O3 is studied using a combination of secondary-ion mass spectrometry, diffusion simulations, and first-principles calculations, and compared to previous studies on Sn diffusion. Ge is implanted into (201)-oriented samples and annealed at temperatures from 900 to 1050 °C for a total of 8 h. From previous first-principles calculations, Sn is predicted to diffuse via the formation of a mobile complex with VGa that migrates through a sequence of exchange and rotation jumps. Herein, it is similarly predicted that Ge diffusion is mediated by VGa. However, the microscopic mechanism differs, as Ge can diffuse more easily through exchange combined with complex dissociation, rather than rotational jumps. This is explained by the difference in Ga-site preference of Ge compared to Sn, and the three-split mechanism that enables low migration barriers for VGa. The dissociation mechanism leads to a considerably faster transport for Ge as compared to Sn. The experimentally obtained Ge diffusion profiles are successfully fitted using a reaction–diffusion model based on the predicted diffusion mechanism, yielding a migration barrier of 2.5 ± 0.2 eV for the complex. The 2.72 eV obtained from first-principles calculations is in good agreement with this value.

• 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
• Gogova, D.; Tran, D.Q.; Stanishev, V.; Jokubavicius, V.; Vines, Lasse & Schubert, M. [Vis alle 9 forfattere av denne artikkelen] (2024). High crystalline quality homoepitaxial Si-doped β-Ga2O3(010) layers with reduced structural anisotropy grown by hot-wall MOCVD. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. ISSN 0734-2101. 42(2). doi: 10.1116/6.0003424. Fulltekst i vitenarkiv
• Samperi, Orazio; Vines, Lasse; Hallén, Anders & Fragalà, Maria Elena (2024). Charge Carrier Capture by Prominent Defect Centers in 4H-SiC. Defect and Diffusion Forum. ISSN 1012-0386. 434, s. 173–182. doi: 10.4028/p-ls2bVE. Fulltekst i vitenarkiv Vis sammendrag

  The knowledge of capture properties of electrically active defects is of primary importance as it helps to understand which deep states are effective in controlling the excess free carriers’ lifetime. Combining DLTS capture experiments with thermal emission measurements enables an overall thermodynamic description of deep states, thus making it possible to characterize recombination centers in semiconductor-based devices. In the present study, junction DLTS capture rate measurements were employed to extract the true capture cross-sections (inversely proportional to the carrier lifetime) and capture energy barriers for the main lifetime limiting defects in 4H-SiC (silicon carbide). A peculiar forward bias dependence of the capture parameters was observed for the shallow boron (B) hole trap. Capture rate measurements on the deep boron (D-center) trap also evidenced the presence of two capture mechanisms, thus allowing discrimination of D1 and D2 deep states within the D-center DLTS peak. The results were combined with activation energies and apparent capture cross-sections to obtain the free energy (ΔG) of electronic activation for the analysed deep states.

• Langørgen, Amanda; Vines, Lasse & Frodason, Ymir Kalmann (2024). Perspective on electrically active defects in β- Ga2O3 from deep-level transient spectroscopy and first-principles calculations. Journal of Applied Physics. ISSN 0021-8979. 135(19). doi: 10.1063/5.0205950. Fulltekst i vitenarkiv Vis sammendrag

  The ultra-wide bandgap of gallium oxide provides a rich plethora of electrically active defects. Understanding and controlling such defects is of crucial importance in mature device processing. Deep-level transient spectroscopy is one of the most sensitive techniques for measuring electrically active defects in semiconductors and, hence, a key technique for progress toward gallium oxide-based components, including Schottky barrier diodes and field-effect transistors. However, deep-level transient spectroscopy does not provide chemical or configurational information about the defect signature and must, therefore, be combined with other experimental techniques or theoretical modeling to gain a deeper understanding of the defect physics. Here, we discuss the current status regarding the identification of electrically active defects in beta-phase gallium oxide, as observed by deep-level transient spectroscopy and supported by first-principles defect calculations based on the density functional theory. We also discuss the coordinated use of the experiment and theory as a powerful approach for studying electrically active defects and highlight some of the interesting but challenging issues related to the characterization and control of defects in this fascinating material.

• Hansen, Ethan R.; Niaouris, Vasileios; Matthews, Bethany E.; Zimmermann, Christian; Wang, Xingyi & Kolodka, Roman [Vis alle 9 forfattere av denne artikkelen] (2024). Isolation of Single Donors in ZnO. Physical Review Letters. ISSN 0031-9007. 133(14). doi: 10.1103/PhysRevLett.133.146902. Fulltekst i vitenarkiv
• 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
• Sozzi, Giovanna; Sapienza, Sergio; Chiorboli, Giovanni; Vines, Lasse; Hallen, Anders & Nipoti, Roberta (2024). Carrier Lifetime Dependence on Temperature and Proton Irradiation in 4H-SiC Device: An Experimental Law. IEEE Access. 12, s. 74230–74238. doi: 10.1109/ACCESS.2024.3405382. Fulltekst i vitenarkiv Vis sammendrag

  The study focuses on analysing the high-level carrier lifetime ( τHL ) in 4H silicon carbide (4H-SiC) PiN diodes under varying temperatures and proton implantation doses. The objective is to identify an empirical law applicable in technology computer-aided design (TCAD) modelling for SiC devices, describing the dependence of carrier lifetime on temperature to gain insights into how irradiation dose may influence the τHL . We electrically characterize diodes of different diameters subjected to different proton irradiation doses and examine the variations in current-voltage (I-V) and ideality factor (n) curves under various irradiation conditions. The effects of proton irradiation on the epitaxial layer are analysed through capacitance-voltage (C-V) measurements. We correlate the observed effects on I-V, n, and C-V curves to the hypothesis of formation of acceptor-type defects related to carbon vacancies, specifically the Z 1/2 defects generated during the irradiation process. The impact of irradiation on carrier lifetime is investigated by measuring τHL using the open circuit voltage decay (OCVD) technique at different temperatures on diodes exposed to various H+ irradiation doses with constant ion energy. This investigation reveals the presence of a proportional relationship between 1/ τHL and the dose of irradiated protons: the proportionality coefficient, referred to as the damage coefficient (K T ), exhibits an Arrhenius-type dependence on temperature. OCVD-measured lifetime on the various diodes demonstrates a power-law dependence of lifetime on temperature. The exponent of this dependence varies with the irradiation dose, notably showing an increase in temperature dependence at the highest H+ ion dose. This suggests a threshold-like dependence on H+ irradiation dose in the τHL -temperature relationship.

• Bugten, Andreas Voll; Miranda, Leander Edward Michels Brito; Brurok, Rune Botnmark; Hartung, Cathrine; Ott, Emmanuelle & Vines, Lasse [Vis alle 9 forfattere av denne artikkelen] (2023). The Role of Boron in Low Copper Spheroidal Graphite Irons. Metallurgical and Materials Transactions A. ISSN 1073-5623. 54, s. 2539–2553. doi: 10.1007/s11661-023-07014-y. Fulltekst i vitenarkiv Vis sammendrag

  The effects of boron at concentrations ranging from 5 to 525 ppm in low copper spheroidal graphite iron (SGI) has been studied. At 130 to 140 ppm, no particular effect of boron was observed on the size distributions, number densities, or morphologies of the microparticle populations in the material. Neither was there observed any effects on the size distributions or number densities of graphite nodules. However, boron was observed to lead to a rough surface morphology of the graphite nodules at concentrations as small as 24 ppm. Intercellular carbides were found to form in alloys containing more than 70 ppm boron. Additionally, the graphite shape began to degenerate in alloys with more than 300 ppm of boron. Mass spectrometry analyses revealed these carbides contain relatively high amounts of boron. In an alloy containing 74 ppm boron, it was inferred by using electron backscatter diffraction that these were of the type borocarbides, where M = Fe, Mn, V, or a combination of them. Mass spectrometry analyses also revealed elevated concentrations of boron in the surface layers of the graphite nodules.

• Saxegaard, Kjetil Karlsen; Monakhov, Eduard; Vines, Lasse & Bergum, Kristin (2023). Characteristics of ZnON films and heterojunction diodes with varying O:N ratios. Thin Solid Films. ISSN 0040-6090. 782. doi: 10.1016/j.tsf.2023.139968. Fulltekst i vitenarkiv Vis sammendrag

  Zinc Oxynitride (ZnOxNy) thin films display high mobilities and a considerable tunability of both the free electron concentration and optical band gap. The properties achievable for this material system makes ZnOxNy an intriguing n-type absorber candidate in silicon-based tandem solar cells. We have studied how the O:N ratio affect structural, optical and electrical properties of magnetron sputtered ZnOxNy thin films, as well the electrical behavior of ZnOxNy-Si pn heterojunction diodes. X-ray diffraction of the ZnOxNy films indicate either a Zn3N2-like structure or ZnO-like grains in combination with structural disorder. As the O:N ratio is increased, the optical band gap of ZnOxNy films increase from 1.1 to 1.9 eV. Hall effect measurements of the n-type ZnOxNy films show free electron concentrations varying with the O:N ratio, from 9.8 × 1017 to 1.5 × 1016 cm−3. Hall mobility up to 88 cm2∕Vs is achieved. We observe the formation of pn heterojunction diodes between ZnOxNy-films and p-Si. The electrical characteristics of these diodes are shown to depend on the ZnOxNy anion composition. Current rectification of 3.7 orders of magnitude is achieved between -1 and 1 V at room temperature. However, the built in voltage extracted from capacitance–voltage measurements are higher than theory suggest, implying an influence of defects on the electrical characteristics.

• Azarov, Alexander; Fernández, Javier García; Zhao, Junlei; Djurabekova, Flyura; He, Huan & He, Ru [Vis alle 13 forfattere av denne artikkelen] (2023). Universal radiation tolerant semiconductor. Nature Communications. 14, s. 1–8. doi: 10.1038/s41467-023-40588-0. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Radiation tolerance is determined as the ability of crystalline materials to withstand the accumulation of the radiation induced disorder. Nevertheless, for sufficiently high fluences, in all by far known semiconductors it ends up with either very high disorder levels or amorphization. Here we show that gamma/beta (γ/β) double polymorph Ga 2 O 3 structures exhibit remarkably high radiation tolerance. Specifically, for room temperature experiments, they tolerate a disorder equivalent to hundreds of displacements per atom, without severe degradations of crystallinity; in comparison with, e.g., Si amorphizable already with the lattice atoms displaced just once. We explain this behavior by an interesting combination of the Ga- and O- sublattice properties in γ-Ga 2 O 3 . In particular, O-sublattice exhibits a strong recrystallization trend to recover the face-centered-cubic stacking despite the stronger displacement of O atoms compared to Ga during the active periods of cascades. Notably, we also explained the origin of the β-to-γ Ga 2 O 3 transformation, as a function of the increased disorder in β-Ga 2 O 3 and studied the phenomena as a function of the chemical nature of the implanted atoms. As a result, we conclude that γ/β double polymorph Ga 2 O 3 structures, in terms of their radiation tolerance properties, benchmark a class of universal radiation tolerant semiconductors.

• Ghezellou, Misagh; Kumar, Piyush; Bathen, Marianne E.; Karsthof, Robert Michael; Sveinbjörnsson, Einar Ö. & Grossner, Ulrike [Vis alle 9 forfattere av denne artikkelen] (2023). The role of boron related defects in limiting charge carrier lifetime in 4H-SiC epitaxial layers. APL Materials. 11(3). doi: 10.1063/5.0142415. Fulltekst i vitenarkiv Vis sammendrag

  One of the main challenges in realizing 4H–SiC (silicon carbide)-based bipolar devices is the improvement of minority carrier lifetime in as-grown epitaxial layers. Although Z1/2 has been identified as the dominant carrier lifetime limiting defect, we report on B-related centers being another dominant source of recombination and acting as lifetime limiting defects in 4H–SiC epitaxial layers. Combining time-resolved photoluminescence (TRPL) measurement in near band edge emission and 530 nm, deep level transient spectroscopy, and minority carrier transient spectroscopy (MCTS), it was found that B related deep levels in the lower half of the bandgap are responsible for killing the minority carriers in n-type, 4H–SiC epitaxial layers when the concentration of Z1/2 is already low. The impact of these centers on the charge carrier dynamics is investigated by correlating the MCTS results with temperature-dependent TRPL decay measurements. It is shown that the influence of shallow B acceptors on the minority carrier lifetime becomes neutralized at temperatures above ∼422 K. Instead, the deep B related acceptor level, known as the D-center, remains active until temperatures above ∼570 K. Moreover, a correlation between the deep level concentrations, minority carrier lifetimes, and growth parameters indicates that intentional nitrogen doping hinders the formation of deep B acceptor levels. Furthermore, tuning growth parameters, including growth temperature and C/Si ratio, is shown to be crucial for improving the minority carrier lifetime in as-grown 4H–SiC epitaxial layers.

• Langørgen, Amanda; Frodason, Ymir Kalmann; Karsthof, Robert Michael; Wenckstern, Holger Von; Jensen, Ingvild Julie Thue & Vines, Lasse [Vis alle 7 forfattere av denne artikkelen] (2023). Defect level in κ-Ga2O3 revealed by thermal admittance spectroscopy. Journal of Applied Physics. ISSN 0021-8979. 134(1), s. 015701-1–015701-6. doi: 10.1063/5.0150994. Fulltekst i vitenarkiv Vis sammendrag

  Defects in pulsed-laser deposition grown have been investigated using thermal admittance spectroscopy and secondary ion mass spectrometry (SIMS). A film was grown on either a tin-doped indium oxide or an aluminum-doped zinc oxide buffer layer on a sapphire substrate functioning as back contact layer in vertical diode structures. In both sample types, a distinct signature in the capacitance signal was observed in the temperature range of 150–260 K. The corresponding defect charge-state transition level, labeled ⁠, was found to exhibit an activation energy of 0.21 eV. Potential candidates for the level were investigated using a combination of SIMS and hybrid-functional calculations. SIMS revealed the main impurities in the sample to be tin, silicon, and iron. The hybrid-functional calculations predict the acceptor levels of substitutional iron to lie 0.7–1.2 eV below the conduction band minimum depending on Ga-site, making an unlikely candidate for the level. Furthermore, Si as well as Sn substituting on the sixfold coordinated Ga2 site and the fivefold coordinated Ga3 and Ga4 sites are all shallow donors in -⁠, similar to that of -⁠. Sn substituting on the fourfold Ga1 site is, however, predicted to have levels in the bandgap at 0.15 and 0.24 eV below the conduction band minimum, in accordance with the extracted activation energy for ⁠. Thus, we tentatively assign as the origin of the level.

• Hommedal, Ylva Knausgård; Frodason, Ymir Kalmann; Vines, Lasse & Johansen, Klaus Magnus H (2023). Trap-limited diffusion of Zn in β-Ga2 O3. PHYSICAL REVIEW MATERIALS. 7(3), s. 1–8. doi: 10.1103/PhysRevMaterials.7.035401. Fulltekst i vitenarkiv Vis sammendrag

  Diffusion of Zn in (001)- and (¯201)-oriented β−Ga2O3 was studied using secondary-ion mass spectrometry and first-principles calculations based on hybrid and semilocal functionals. The β−Ga2O3 samples were sealed in quartz ampules together with a piece of metallic Zn and heated to temperatures of 900–1100 ∘C for 1 h. The Zn concentration profiles as a function of depth were simulated by employing the trap-limited diffusion model. From this model the migration barrier for Zn diffusion was found to be Em=2.2±0.2 and 2.1±0.1eV in the (001) and (¯201) orientations of β−Ga2O3, respectively, with corresponding dissociation energies of Ed = 3.5 ±1.1 and 3.2±0.6eV. Results from the first-principles calculations predict an interstitialcy mechanism for the Zn diffusion when it is not in its trapped state. Using the nudged elastic band method, we obtain a barrier of 1.6 eV for migration of Zn split interstitials (Zni) in both the [001] and [¯201] directions, in accordance with the results obtained from the trap-limited diffusion model. Interestingly, the Ga vacancy is found to be able to trap two Zn atoms forming a shallow donor complex labeled ZniZnGa. The energy needed for Zni to dissociate from this donor complex is estimated to be 2.99 eV, in reasonable agreement with the trap dissociation energies extracted from the diffusion model.

• Frodason, Ymir Kalmann; Varley, Joel B.; Johansen, Klaus Magnus H; Vines, Lasse & Walle, Chris G. Van De (2023). Migration of Ga vacancies and interstitials in β-Ga2 O3. Physical review B (PRB). ISSN 2469-9950. 107(2), s. 024109-1–024109-9. doi: 10.1103/PhysRevB.107.024109. Fulltekst i vitenarkiv Vis sammendrag

  Pathways and energy barriers for the migration of Ga vacancies (VGa) and Ga interstitials (Gai) in β−Ga2O3 are explored using hybrid functional calculations and the nudged elastic band method. Considering β−Ga2O3 as primarily being an n-type semiconductor, we focus on defect charge states relevant under such conditions: V3−Ga, Ga3+i, and Ga+i. Notably, we describe a mechanism by which VGa can transform between its different split configurations. In all cases, the intermediate state consists of a vacancy split between three Ga sites—a three-split vacancy—which enables passage over a significantly lower energy barrier. This is because it avoids the unfavorable simple vacancy at the tetrahedral Ga site. The proposed mechanism lowers the overall barrier for V3−Ga diffusion along the [001] crystal direction from 1.73 to 0.97 eV, whereas the 2.08 eV barrier for the [100] and [010] directions is unaffected. For Ga3+i, we obtain similar overall migration barriers of 0.72, 0.80, and 1.02 eV for the [010], [001], and [100] directions, respectively. Ga+i exhibits a strong preference for diffusion within the large eight-sided channel; the overall migration barrier is 0.92 eV for the [010] direction, and 2.16 eV for the [001] and [100] directions. The limiting step for the two latter directions involves ionization of Ga+i followed by a jump to an adjacent large eight-sided channel as Ga3+i. Our results are discussed in light of experimental observations of thermally activated recovery processes in irradiated material.

• Bathen, Marianne Etzelmüller; Selnesaunet, Gard Momrak; Enga, Marius; Kjeldby, Snorre Braathen; Müting, Johanna & Vines, Lasse [Vis alle 7 forfattere av denne artikkelen] (2023). Charge State Control Over Point Defects in SiC Devices. Defect and Diffusion Forum. ISSN 1012-0386. 425, s. 35–42. doi: 10.4028/p-6ho92o. Fulltekst i vitenarkiv Vis sammendrag

  Point defects in silicon carbide (SiC) are well positioned for integration with SiC based quantum photonic devices due to the maturity of SiC material and fabrication technology, the plethora of candidate quantum emitters that can be formed in SiC, and the potential for emission over a wide spectral range from the visible to the infrared. However, for each of the available color centers in SiC, only one of the charge states has displayed quantum emission, meaning that the emission strongly depends on the Fermi level and hence the doping concentration in the material. In this contribution, we discuss the methodology and mechanism for electrical charge-state control over point defects in SiC devices.

• Wang, Xingyi; Zimmermann, Christian; Titze, Michael; Niaouris, Vasileios; Hansen, Ethan R. & D'Ambrosia, Samuel H. [Vis alle 9 forfattere av denne artikkelen] (2023). Properties of Donor Qubits in ZnO Formed by Indium-Ion Implantation. Physical Review Applied. 19(5), s. 054090-1–054090-12. doi: 10.1103/PhysRevApplied.19.054090. Fulltekst i vitenarkiv Vis sammendrag

  Neutral shallow donors (D0) in ZnO have emerged as a promising candidate for solid-state spin qubits. Here we report on the formation of D0 in ZnO via implantation of In and subsequent annealing. The implanted In donors exhibit optical and spin properties on par with those of in situ–doped donors. The inhomogeneous linewidth of the donor-bound-exciton transition is less than 10 GHz, comparable to the optical linewidth of in situ In. Longitudinal spin relaxation times (T1) exceed reported values for in situ Ga donors, indicating that residual In-implantation damage does not degrade T1. Two-laser Raman spectroscopy of the donor spin reveals the hyperfine interaction of the donor electron with the spin-9/2 In nuclei. This work is an important step toward the deterministic formation of In-donor qubits in ZnO with optical access to a long-lived nuclear-spin memory.

• Borgersen, Jon; Karsthof, Robert Michael; Rønning, Vegard; Vines, Lasse; Wenckstern, Holger Von & Grundmann, Marius [Vis alle 8 forfattere av denne artikkelen] (2023). Origin of enhanced conductivity in low dose ion irradiated oxides. AIP Advances. 13(1), s. 015211-1–015211-5. doi: 10.1063/5.0134699. Fulltekst i vitenarkiv Vis sammendrag

  Significant resistivity variations have previously been observed in oxides subjected to relatively low ion irradiation doses, nominally insufficient to generate the amount of bulk defects needed to explain the phenomena. In an effort to unveil the underlying mechanisms, we performed a systematic comparative study of the resistivity evolution in In 2 O 3 -based oxides as a function of low ion doses and ultraviolet (UV) illumination, observing striking correlations. Specifically, we found that irradiation with ∼3 × 10 12  Si/cm 2 and ∼18 h UV exposure result in similar resistivity drops, interpreted in terms of irradiation/illumination assisted desorption of oxygen containing species from the surface. This was further proven by post-irradiation exposure of one of the samples to an oxygen atmosphere partially restoring the resistivity. Combining the present results with literature data, we conclude that the radiation tolerance of In 2 O 3 -based and similar oxides depends on the surface charge modifications, individual defect contributions, and contributions from defect complexes at low, intermediate, and high doses, respectively.

• Linnarsson, Margareta; Vines, Lasse & Hallen, Anders (2023). Al Implantation in SiC; Where Will the Ions Come to Rest? Solid State Phenomena. ISSN 1012-0394. 343, s. 57–64. doi: 10.4028/p-nxe4cz. Fulltekst i vitenarkiv Vis sammendrag

  In all implantations into crystalline targets, quite a few ions find a path along a crystal channel or plane, so called channeling, and these ions travel deep into the crystal. This paper treats aluminum (Al) implantation in 4H-SiC and show how the crystal lattice will guide incoming ions deep into the target and modify the final dopant distribution. 4H-SiC samples have been implanted with 100 keV Al-ions, in a “random” direction using the wafer miscut angle of 4°, as well as with the impact beam aligned anti-parallel to the [0001] direction. Aluminium concentration versus depth profiles has been recorded by secondary ion mass spectrometry (SIMS). To track the most probable ion paths during stopping process, SIIMPL, a Monte Carlo simulation code based on the binary collision approximation (MC-BCA) has been used. In addition, the remaining ion energy has been extracted from SIIMPL at various depth along the ion path. Our results show that, independent of the used impact angle, some ions will be steered by crystal planes predominantly into the direction and also along the six directions. The energy loss is smaller along these low index axes. Therefore, at a depth of 1.2 μm, some Al ions along a path may still have kinetic energy, more than 40% of the original 100 keV, and continues to move deep into the SiC sample. The mean projected range of 100 keV ions in 4H-SiC is about 120 nm.

• Serra, Filipe; Gaspar, Guilherme; Viana, Ana; Arumughan, Jayaprasad; Costa, Ivo & Pêra, David [Vis alle 10 forfattere av denne artikkelen] (2023). Gas immersion laser doping: N++ phosphorus doping on p+ Cz-Si wafers with a highly doped p++ emitter. AIP Conference Proceedings. ISSN 0094-243X. 2826. doi: 10.1063/5.0140455. Fulltekst i vitenarkiv
• Frodason, Ymir Kalmann; Krzyzaniak, Patryk Piotr; Vines, Lasse; Varley, Joel Basile; Walle, Chris G. Van De & Johansen, Klaus Magnus H (2023). Diffusion of Sn donors in β-Ga2O3. APL Materials. 11(4), s. 041121-1–041121-8. doi: 10.1063/5.0142671. Fulltekst i vitenarkiv Vis sammendrag

  Diffusion of the n-type dopant Sn in β-Ga2O3 is studied using secondary-ion mass spectrometry combined with hybrid functional calculations. The diffusion of Sn from a Sn-doped bulk substrate with surface orientation (001) into an epitaxial layer is observed after heat treatments in the temperature range of 1050–1250 °C. Calculated formation energies of Sn-related and intrinsic defects show that the migration of Sn is mediated by Ga vacancies (VGa) through the formation and dissociation of intermittent mobile VGaSnGa complexes. The evolution of the Sn concentration vs depth profiles after heat treatments can be well described by a reaction–diffusion model. Using model parameters guided by the hybrid functional calculations, we extract a VGaSnGa complex migration barrier of 3.0 ± 0.4 eV with a diffusion coefficient of 2 × 10−1 cm2/s. The extracted migration barrier is consistent with our theoretical predictions using the nudged elastic band method, which shows migration barriers of 3.42, 3.15, and 3.37 eV for the [100], [010], and [001] directions, respectively.

• Polyakov, A.Y.; Kochkova, A.I.; Langørgen, Amanda; Vines, Lasse; Vasilev, A. & Shchemerov, I.V. [Vis alle 8 forfattere av denne artikkelen] (2023). On the possible nature of deep centers in Ga2O3. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. ISSN 0734-2101. 41(2), s. 023401-1–023401-6. doi: 10.1116/6.0002307. Fulltekst i vitenarkiv Vis sammendrag

  The electric field dependence of emission rate of the deep traps with level near Ec−0.6 eV, so-called E1 traps, was studied by means of deep level transient spectroscopy measurements over a wide range of applied voltages. The traps were initially introduced by 900 °C ampoule annealing in molecular hydrogen. The results indicate the activation energy of the centers and the ratio of high-field to low-field electron emission rates at a fixed temperature scale as the square root of electric field, suggesting that the centers behave as deep donors. The possible microscopic nature of the centers in view of recent theoretical calculations is discussed. The most likely candidates for the E1 centers are SiGa1–H or SnGa2–H complexes.

• 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.

• Seyidov, Palvan; Varley, Joel B.; Frodason, Ymir Kalmann; Klimm, Detlef; Vines, Lasse & Galazka, Zbigniew [Vis alle 10 forfattere av denne artikkelen] (2023). Thermal Stability of Schottky Contacts and Rearrangement of Defects in β-Ga2O3 Crystals. Advanced Electronic Materials. doi: 10.1002/aelm.202300428. Fulltekst i vitenarkiv Vis sammendrag

  Abstract The thermal stability of different Schottky contacts (Au, Pt, and Ni) on (100) β ‐Ga 2 O 3 single crystals grown by the Czochralski method is investigated. Besides the examination of the Schottky barrier parameters, contact‐dependent defect levels are investigated by deep‐level transient spectroscopy (DLTS) in a 100–650 K (ramp‐up) and 650–100 K (ramp‐down) temperature cycle. Several defect levels are detected below the conduction band minimum at 0.41, 0.60, 0.77, 0.96, and 1.17 eV. In the temperature ramp‐down DLTS, the 1.17 eV level disappears, and the 0.60 eV level appears for all Schottky contacts. DFT calculations suggest that rearrangement and dissociation of a single hydrogen from a doubly‐hydrogenated Ga─O divacancy complex occurs during the temperature sweep under bias. The trap level at 0.96 eV only appears after the thermal load for the Ni contact, in contrast to Au and Pt, where it is present without a thermal budget. Temperature‐dependent leakage current (at −4 V) measurements indicate oxidation of Ni, and further thermodynamic analysis suggests alloying of Au‐Ga atoms at the Au/ β ‐Ga 2 O 3 interface. These studies provide insight into the behavior induced by these common Schottky contacts and the alteration associated with temperature cycling.

• Olsen, Vegard Skiftestad; Frodason, Ymir Kalmann; Hommedal, Ylva Knausgård; Nielsen, Dina Marie; Weiser, Philip Michael & Johansen, Klaus Magnus H [Vis alle 9 forfattere av denne artikkelen] (2022). Li and group-III impurity doping in ZnSnN2: Potential and limitations. PHYSICAL REVIEW MATERIALS. 6(12), s. 1–8. doi: 10.1103/PhysRevMaterials.6.124602. Fulltekst i vitenarkiv Vis sammendrag

  II–IV nitrides and their alloys represent an earth-abundant and potentially cost-efficient alternative to the well-developed AlN-GaN-InN system. A major drawback with the II–IV nitrides is that ZnSnN2, the lowest band gap material, exhibits unfavorably high carrier concentrations for as-grown, stoichiometric material, limiting the material systems potential use in applications such as solar cells and light-emitting diodes. Lithium (Li) has been suggested as a shallow acceptor defect in ZnSnN2 if substituting for Zn, and hence doping with Li has been identified as a possible way to improve the electronic properties. Herein, theoretical calculations by hybrid functional density functional theory have been employed and extended to include defect complexes as well, which to this point remained unexplored. The calculations reveal that even though Li on the Zn site (the LiZn) is an acceptor, the defect may easily complex with the Lii donor, rendering the complex neutral. Our theoretical findings are supported by a Li-doping series of ZnSnN2, where a doping concentration ranging from 2.10×1019cm−3 to 1.85×1020cm−3 was obtained. The n-type carrier concentration was found to be unaffected by the doping concentration, and no systematic change in the absorption onset, probably affected by a Burstein-Moss shift, was observed. Possible group-III dopants, as have been found to yield interesting results for ZnGeN2, such as In, Ga, Al, and B, have also been investigated as an alternative dopant in ZnSnN2.

• Kjeldby, Snorre Braathen; Azarov, Alexander; Nguyen, Phuong Dan; Venkatachalapathy, Vishnukanthan; Mikšová, R. & MacKová, A. [Vis alle 9 forfattere av denne artikkelen] (2022). Radiation-induced defect accumulation and annealing in Si-implanted gallium oxide. Journal of Applied Physics. ISSN 0021-8979. 131(12). doi: 10.1063/5.0083858. Fulltekst i vitenarkiv Vis sammendrag

  Defect accumulation and annealing phenomena in Si-implanted monoclinic gallium oxide (β-Ga 2 O 3 ) wafers, having [Formula: see text], (010), and (001) orientations, were studied by Rutherford backscattering spectrometry in channeling mode (RBS/c), x-ray diffraction (XRD), and (scanning) transmission electron microscopy [(S)TEM]. Initially, the samples with different surface orientations were implanted with 300 keV 28 Si + -ions, applying fluences in the range of 1 × 10 14 –2 × 10 16  Si/cm 2 , unveiling interesting disorder accumulation kinetics. In particular, the RBS/c, XRD, and (S)TEM combined data suggested that the radiation disorder buildup in Si-implanted β-Ga 2 O 3 is accompanied by significant strain accumulation, assisting crystalline-to-crystalline phase transitions instead of amorphization. Selected samples having [Formula: see text] orientation were subjected to isochronal (30 min) anneals in the range of 300–1300 °C in air. Systematic RBS/c and XRD characterization of these samples suggested complex structural transformations, which occurred as a function of the fluence and the temperature. Moreover, a detailed (S)TEM analysis of the sample implanted with 2 × 10 16  Si/cm 2 and annealed at 1100 °C was enhanced by applying dispersive x-ray and electron energy-loss spectroscopies. The analysis revealed silicon agglomerations in the form of silicon dioxide particles. Signal from silicon was also detected outside of the agglomerates, likely occurring as substitutional Si on Ga sites.

• 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.

• Langørgen, Amanda; Zimmermann, Christian; Frodason, Ymir Kalmann; Verhoeven, Espen Førdestrøm; Weiser, Philip Michael & Karsthof, Robert Michael [Vis alle 8 forfattere av denne artikkelen] (2022). Influence of heat treatments in H2 and Ar on the E1 center in β-Ga2O3. Journal of Applied Physics. ISSN 0021-8979. 131(115702). doi: 10.1063/5.0083861. Fulltekst i vitenarkiv Vis sammendrag

  The influence of heat treating [Formula: see text]-type bulk [Formula: see text]-Ga[Formula: see text]O[Formula: see text] in hydrogen (H[Formula: see text]) and argon (Ar) gases on the presence of the defect level commonly labeled as [Formula: see text] was studied. Fourier transform-infrared spectroscopy confirms that hydrogen (H) is incorporated into [Formula: see text]-Ga[Formula: see text]O[Formula: see text] during H[Formula: see text] annealing at 900 °C. Deep-level transient spectroscopy measurements reveal that the concentration of the [Formula: see text] level is promoted by the introduction of H, in contrast to what is observed in samples heat-treated in an Ar flow. We further find the [Formula: see text] level to be stable against heat treatments at 650 K, both with and without an applied reverse-bias voltage. Potential candidates for the defect origin of [Formula: see text] are investigated using hybrid-functional calculations, and three types of defect complexes involving H are found to exhibit charge-state transition levels compatible with [Formula: see text], including substitutional H at one of the threefold coordinated O sites, Ga-substitutional shallow donor impurities passivated by H, and certain configurations of singly hydrogenated Ga–O divacancies. Among these types, only the latter exhibit H binding energies that are consistent with the observed thermal stability of [Formula: see text].

• Assar, Alireza; Martinho, Filipe; Larsen, Jes; Saini, Nishant; Shearer, Denver & Moro, Marcos V. [Vis alle 15 forfattere av denne artikkelen] (2022). Gettering in polySi/SiO xpassivating contacts enables Si-based tandem solar cells with high thermal and contamination resilience. ACS Applied Materials & Interfaces. ISSN 1944-8244. 14(12), s. 14342–14358. doi: 10.1021/acsami.2c00319. Fulltekst i vitenarkiv Vis sammendrag

  Multijunction solar cells in a tandem configuration could further lower the costs of electricity if crystalline Si (c-Si) is used as the bottom cell. However, for direct monolithic integration on c-Si, only a restricted number of top and bottom cell architectures are compatible, due to either epitaxy or high-temperature constraints, where the interface between subcells is subject to a trade-off between transmittance, electrical interconnection, and bottom cell degradation. Using polySi/SiOx passivating contacts for Si, this degradation can be largely circumvented by tuning the polySi/SiOx stacks to promote gettering of contaminants admitted into the Si bottom cell during the top cell synthesis. Applying this concept to the low-cost top cell chalcogenides Cu2ZnSnS4 (CZTS), CuGaSe2 (CGSe), and AgInGaSe2 (AIGSe), fabricated under harsh S or Se atmospheres above 550 °C, we show that increasing the heavily doped polySi layer thickness from 40 to up to 400 nm prevents a reduction in Si carrier lifetime by 1 order of magnitude, with final lifetimes above 500 μs uniformly across areas up to 20 cm2. In all cases, the increased resilience was correlated with a 99.9% reduction in contaminant concentration in the c-Si bulk, provided by the thick polySi layer, which acts as a buried gettering layer in the tandem structure without compromising the Si passivation quality. The Si resilience decreased as AIGSe > CGSe > CZTS, in accordance with the measured Cu contamination profiles and higher annealing temperatures. An efficiency of up to 7% was achieved for a CZTS/Si tandem, where the Si bottom cell is no longer the limiting factor.

• Hebnes, Oliver Lerstøl; Bathen, Marianne Etzelmüller; Schøyen, Øyvind Sigmundson; Winther-Larsen, Sebastian Gregorius; Vines, Lasse & Hjorth-Jensen, Morten (2022). Predicting solid state material platforms for quantum technologies. npj Computational Materials. 8(1). doi: 10.1038/s41524-022-00888-3. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Semiconductor materials provide a compelling platform for quantum technologies (QT). However, identifying promising material hosts among the plethora of candidates is a major challenge. Therefore, we have developed a framework for the automated discovery of semiconductor platforms for QT using material informatics and machine learning methods. Different approaches were implemented to label data for training the supervised machine learning (ML) algorithms logistic regression, decision trees, random forests and gradient boosting. We find that an empirical approach relying exclusively on findings from the literature yields a clear separation between predicted suitable and unsuitable candidates. In contrast to expectations from the literature focusing on band gap and ionic character as important properties for QT compatibility, the ML methods highlight features related to symmetry and crystal structure, including bond length, orientation and radial distribution, as influential when predicting a material as suitable for QT.

Se alle arbeider i NVA

• Vines, Lasse; Frøland, Mariann Carlsen & Stokke, Anne-Marie Korseberg (2026). Coffee & Chips - Quantum technology initiatives in Norway and the center for Defects in Semiconductors for Quantum Sensing (UiO). doi: https:/www.forskningsparken.no/event/coffee-chip-may-26. Fulltekst i vitenarkiv
• Frøland, Mariann Carlsen; Furlan, Riccardo; Bygdås, Martin; Olsen, Vegard Standeren; Bathen, Marianne Etzelmüller & Vines, Lasse (2026). Sputtered Aluminum Nitride Thin Films as Waveguides and Hosts for Single-Photon Emitters. Fulltekst i vitenarkiv Vis sammendrag

  AlN is a promising material for hosting quantum emitters and for use as optical waveguides. This work investigates the emission and structural properties of sputtered aluminium nitride thin films, with the aim of integrating these films into a quantum sensor.

• Bygdås, Martin; Zalandauskas, Vytautas; Frøland, Mariann Carlsen; Farsund, Øystein; Vines, Lasse & Bathen, Marianne Etzelmüller (2026). Intrinsic defects in AlN for single-photon emission and spin manipulation. Fulltekst i vitenarkiv Vis sammendrag

  AlN is a promising host for quantum emitters, with an ultra-wide band gap, piezoelectric properties and widely used in industry. Recent reports indicate the presence of single-photon emitters (SPEs) in AlN [1,2], but the responsible defects are unidentified. This work aims to contribute towards such an identification by modelling intrinsic defects in AlN and their magneto-optical properties using density functional theory (DFT).

• Bazioti, Kalliopi; Azarov, Alexander; Vines, Lasse; Prytz, Øystein & Kuznetsov, Andrej (2026). Fundamental insights into polymorphism and defect evolution in ion-irradiated semiconductors by employing atomic-scale Transmission Electron Microscopy. Fulltekst i vitenarkiv
• Langørgen, Amanda; Frodason, Ymir Kalmann; Zimmermann, Christian; Karsthof, Robert Michael; Weiser, Philip Michael & Jensen, Ingvild Julie Thue [Vis alle 7 forfattere av denne artikkelen] (2025). Seminar talk - Electrically active defects in β-Ga2O3. Fulltekst i vitenarkiv
• Kjeldby, Snorre Braathen; Olsen, Vegard Skiftestad; Frodason, Ymir Kalmann; Zacharaki, Eirini; Cooil, Simon Phillip & Vines, Lasse [Vis alle 12 forfattere av denne artikkelen] (2025). Thin film top cell absorbers for multijunction solar cells. Fulltekst i vitenarkiv
• Bathen, Marianne Etzelmüller; Olsen, Vegard Skiftestad & Vines, Lasse (2024). Hvor går veien? Kvanteteknologiens potensiale i fremtidens teknologi​. Fulltekst i vitenarkiv
• Fernandez, Javier Garcia; Kjeldby, Snorre Braathen; Zeng, L. J.; Olsson, E.; Vines, Lasse & Prytz, Øystein (2024). Structural Transformation in Ge+ Implanted β-Ga2O3: Functionalization with Ge Nanoparticles leading to 'Emmental-type' Nano-architecture. Fulltekst i vitenarkiv
• Bathen, Marianne Etzelmüller; Hebnes, Oliver Lerstøl; Schøyen, Øyvind; Winther-Larsen, Sebastian G.; Vines, Lasse & Hjorth-Jensen, Morten (2024). Predicting solid state material platforms for quantum technologies. Fulltekst i vitenarkiv
• Bathen, Marianne Etzelmüller & Vines, Lasse (2024). Semiconductors as quantum materials - Ongoing research at the LENS group. Fulltekst i vitenarkiv
• Ousdal, Erlend Lemva; Bathen, Marianne Etzelmüller & Vines, Lasse (2024). Control and tuning of emission from point defects in silicon carbide using an applied electric field. 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
• Langørgen, Amanda; Frodason, Ymir Kalmann; Jensen, Ingvild Julie Thue & Vines, Lasse (2024). A metastable deep defect in 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
• Hommedal, Ylva Knausgård; Frodason, Ymir Kalmann; Vines, Lasse & Johansen, Klaus Magnus H (2023). Ge donor diffusion in β-Ga2O3. Fulltekst i vitenarkiv
• Hommedal, Ylva Knausgård; Frodason, Ymir Kalmann; Vines, Lasse & Johansen, Klaus Magnus H (2023). Impurity diffusion in β-Ga2O3. Fulltekst i vitenarkiv
• Fernandez, Javier Garcia; Kjeldby, Snorre Braathen; Azarov, Alexander; Pokle, Anuj; Nguyen, Phuong Dan & Vines, Lasse [Vis alle 8 forfattere av denne artikkelen] (2023). Polymorph engineering and radiation tolerance in β-Ga2O3. Fulltekst i vitenarkiv
• Kjeldby, Snorre Braathen; Fernández, Javier García; Nguyen, Phuong Dan; Prytz, Øystein & Vines, Lasse (2023). Implantation for polymorphic transformation in Ga2O3: thermal evolution and luminescence. Fulltekst i vitenarkiv Vis sammendrag

  Dette foredraget presenterer ioneimplantasjonindusert fasetransformasjon i galliumoksid, Ga2O3, fra beta-fasen til gamma-fasen. Den siste tiden har det vært utbredt vitenskaplig interesse i denne transformasjonen, som, basert på tilgjengelige data, ser ut til å være uavhengig av det implanterte speciet. Utover å presentere forsøk som fastslår den termiske stabiliteten til gamma-fasen, opp til 500 eller 700 grader Celsius avhengig av implantasjonsparametre, presenterer vi her også de første luminesensmålingene på slike prøver med høy romlig oppløsning, hovedsaklig fra prøver implantert med germanium, med støttende resultater fra nikkelimplanterte prøver. Både intrinsisk luminesens, fra selvlokaliserte hull og intrinsiske defekter, og ekstrinsisk luminesens fra krom ble studert. Foredraget bidrar til å klargjøre ikke bare strukturen men også egenskapene til fasetransformerte lag i galliumoksid fra ioneimplantasjon.

• Ousdal, Erlend Lemva; Bathen, Marianne Etzelmüller & Vines, Lasse (2023). Controlling directionality of emission from quantum defects through microstructures in Silicon Carbide. Fulltekst i vitenarkiv
• Ousdal, Erlend Lemva; Bathen, Marianne Etzelmüller & Vines, Lasse (2023). Optical and electrical characterization of potential single photon emitters in 6H silicon carbide. Fulltekst i vitenarkiv
• Saxegaard, Kjetil Karlsen; Bergum, Kristin; Vines, Lasse & Monakhov, Eduard (2023). The effect of annealing on opto-electronic properties of ZnON films. Fulltekst i vitenarkiv
• Monakhov, Eduard; Bergum, Kristin; Vines, Lasse & Saxegaard, Kjetil Karlsen (2023). The UiO semiconductor group: Towards tandems with ZnON. Fulltekst i vitenarkiv
• Saxegaard, Kjetil Karlsen; Monakhov, Eduard; Vines, Lasse & Bergum, Kristin (2023). The effect of annealing on ZnON intended for solar cell applications. Fulltekst i vitenarkiv
• Langørgen, Amanda; Frodason, Ymir Kalmann; Jensen, Ingvild Julie Thue & Vines, Lasse (2023). A metastable deep defect in beta-Ga2O3. Fulltekst i vitenarkiv
• Bathen, Marianne Etzelmüller & Vines, Lasse (2023). Studieretning i kvanteteknologi​. Fulltekst i vitenarkiv
• Bathen, Marianne Etzelmüller & Vines, Lasse (2023). Point defects in semiconductors for quantum technologies​ ​ Ongoing research at ​ the University of Oslo​. 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
• Bathen, Marianne Etzelmüller; Razinkovas, Lukas; Linderälv, Christopher; Vines, Lasse & Grossner, Ulrike (2023). Quantum pressure sensing using the vibronic spectrum of color centers. Fulltekst i vitenarkiv
• Bathen, Marianne Etzelmüller; Kumar, Piyush; Ghezellou, Misagh; Belanche, Manuel; Vines, Lasse & Ul-Hassan, Jawad [Vis alle 7 forfattere av denne artikkelen] (2023). Dual configuration of shallow acceptor levels in 4H-SiC. Fulltekst i vitenarkiv
• Hommedal, Ylva Knausgård; Frodason, Ymir Kalmann; Vines, Lasse & Johansen, Klaus Magnus H (2022). Zn diffusion in 𝛽-Ga2O3 using SIMS. Fulltekst i vitenarkiv
• Saxegaard, Kjetil Karlsen; Bergum, Kristin; Monakhov, Eduard & Vines, Lasse (2022). The effect of oxygen and nitrogen concentrations on Opto-electronic properties of ZnON films. 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
• Bathen, Marianne Etzelmüller; Hebnes, Oliver Lerstøl; Schøyen, Øyvind Sigmundson; Winther-Larsen, Sebastian Gregorius; Vines, Lasse & Hjorth-Jensen, Morten (2022). Predicting Solid State Material Platforms for Quantum Technologies. Fulltekst i vitenarkiv
• Karlsen, Kjetil; Bergum, Kristin; Monakhov, Eduard & Vines, Lasse (2022). The effect of oxygen and nitrogen concentrations on Opto-electronic properties of ZnON films. Fulltekst i vitenarkiv
• Bergum, Kristin; Monakhov, Eduard & Vines, Lasse (2022). The effect of oxygen and nitrogen concentrations on Opto-electronic properties of ZnON films. Fulltekst i vitenarkiv
• Karlsen, Kjetil; Bergum, Kristin; Monakhov, Eduard & Vines, Lasse (2022). The effect of oxygen and nitrogen concentrations on Opto-electronic properties of ZnOxNy films. Fulltekst i vitenarkiv
• Karlsen, Kjetil; Bergum, Kristin; Monakhov, Eduard & Vines, Lasse (2022). Electronic properties and dominant levels in ZnON. Fulltekst i vitenarkiv
• Karlsen, Kjetil; Bergum, Kristin; Monakhov, Eduard & Vines, Lasse (2022). The effect of oxygen and nitrogen concentrations on Opto-electronic properties of ZnON films. Fulltekst i vitenarkiv
• Hommedal, Ylva Knausgård; Frodason, Ymir Kalmann; Vines, Lasse & Johansen, Klaus Magnus H (2022). Diffusion of Zn in beta-Ga2O3. Fulltekst i vitenarkiv
• Hommedal, Ylva Knausgård; Frodason, Ymir Kalmann; Vines, Lasse & Johansen, Klaus Magnus H (2022). Dynamic interaction of Zn and intrinsic defects in beta-Ga2O3. 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.

• Frodason, Ymir Kalmann; Varley, Joel Basile; Johansen, Klaus Magnus H; Vines, Lasse & Walle, Chris G. Van de (2022). Strongly anisotropic migration of the Ga vacancy in ß-Ga2O3. Fulltekst i vitenarkiv
• Frodason, Ymir Kalmann; Krzyzaniak, Patryk Piotr; Vines, Lasse; Varley, Joel Basile; Walle, Chris G. Van de & Johansen, Klaus Magnus H (2022). Ga vacancy-mediated diffusion of Sn donors in β-Ga2O3. Fulltekst i vitenarkiv
• Bergum, Kristin; Monakhov, Eduard & Vines, Lasse (2022). The effect of oxygen and nitrogen concentrations on Opto-electronic properties of ZnOxNy films. Fulltekst i vitenarkiv
• Jones, Ella Randmæl; Prytz, Øystein; Vines, Lasse; Elgvin, Cana & Both, Kevin Gregor (2024). Pulsed laser deposition synthesis of ZnFe2O4 nanostructures embedded in a ZnO thin film for tandem solar cells. University of Oslo, Department of Physics. Fulltekst i vitenarkiv
• Kjeldby, Snorre Braathen; Vines, Lasse & Prytz, Øystein (2024). Polymorph transformations, nanoparticles, and luminescence in ion-implanted gallium oxide. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  Gallium oxide is a promising ultra wide band gap semiconductor for applications in power electronics, photodetectors, and as a transparent host material or electrical conductor. Ion implantation is a technique used to tailor the properties of semiconductors. For further technological development of gallium oxide, it is therefore essential to understand how the material is affected by ion implantation. Crystalline materials typically lose their crystal structure after high-dose ion implantation, while gallium oxide instead transforms to a different crystal structure. In this thesis, we investigate the transformation, and show that initially monoclinic gallium oxide transforms to the defective spinel polymorph. The results reveal that the polymorph transformation is independent of the implanted species and is caused by the implantation-induced defect formation, rather than the chemistry of the implanted ions. Further, the transformation can be reversed through heat treatments. The work also reveals that germanium and silicon dioxide nanoparticles can be embedded in gallium oxide with ion implantation followed by annealing. The luminescence from implanted and annealed gallium oxide, including Cr-related luminescence, has been probed with high spatial resolution. These results advance the understanding of polymorph transformations from ion implantation and elucidate several important aspects of ion implantation in gallium oxide

• Skaar, Lars Kristian Gretland; Vines, Lasse & Gongora, David Rivas (2023). Formation of W-, C- and G-centers in silicon; towards single photon emitters. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  Quantum technology utilize the fundamental properties of quantum mechanics in devices and applications. The most known fields of quantum technology include quantum computing, quantum sensing and quantum communication. Today, the communication between the individual devices are limited by the ability to transfer quantum information across larger distances. A solution for this problem is the development of single-photon emitters (SPEs) and to use individual photons to transfer the information. One quantum technology platform for such SPEs are quantum defects in semiconducting materials, where the emission can also be used to read out the state of the quantum defect, or qubit. The recent discoveries of SPEs in silicon have spiked an interest of the material as a potential host for SPEs. In this research, PL and DLTS have been used to examine the W-, C- and G-center to create the centers in low concentrations to prepare for future single-photon measurements. Systematic proton implantation and post-implant annealing resulted in successful formation of the centers in both FZ and CZ grown samples. The centers showed varying PL intensity depending on the implantation parameters and annealing method. DLTS measurements on the C-center in epitaxially grown samples resulted in a defect concentration of ∼ 2E13 cm−3 for samples implanted with a proton energy of 1.8 MeV and fluence of 1E13 cm−2. This low concentration of defects is promising for future single-photon measurements on individual centers.

• Vigneswaran, Nirun; Vines, Lasse & Olsen, Vegard Skiftestad (2022). Deponering og karakterisering av polykrystallinsk SnO for solcelle applikasjoner. Universitetet i Oslo. Fulltekst i vitenarkiv
• Pedersen, Benedicte Allum; Vines, Lasse; Kjeldby, Snorre Braathen & Reinertsen, Vilde Mari (2022). Positioning and control of single-photon emitters in SiC-based nanostructures for quantum applications. Universitetet i Oslo. Fulltekst i vitenarkiv

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