arvind

• Vines, Lasse; Bhoodoo, Chidanand; Wenckstern, H Von & Grundmann, M (2018). Electrical conductivity of In2O3 and Ga2O3 after low temperature ion irradiation; Implications for instrinsic defect formation and charge neutrality level. Journal of Physics: Condensed Matter. ISSN 0953-8984. 30(2). doi: 10.1088/1361-648X/aa9e2a. Fulltekst i vitenarkiv Vis sammendrag

  The evolution of sheet resistance of n-type In2O3 and Ga2O3 exposed to bombardment with MeV 12C and 28Si ions at 35 K is studied in situ. While the sheet resistance of Ga2O3 increased by more than eight orders of magnitude as a result of ion irradiation, In2O3 showed a more complex defect evolution and became more conductive when irradiated at the highest doses. Heating up to room temperature reduced the sheet resistivity somewhat, but Ga2O3 remained highly resistive, while In2O3 showed a lower resistance than as deposited samples. Thermal admittance spectroscopy and deep level transient spectroscopy did not reveal new defect levels for irradiation up to $2 \times 10^{12}$ cm−2. A model where larger defect complexes preferentially produce donor like defects in In2O3 is proposed, and may reveal a microscopic view of a charge neutrality level within the conduction band, as previously proposed.

• Bhoodoo, Chidanand; Vines, Lasse; Monakhov, Edouard & Svensson, Bengt Gunnar (2017). Diffusivity of the double negatively charged mono-vacancy in silicon. Journal of Physics: Condensed Matter. ISSN 0953-8984. 29(20). doi: 10.1088/1361-648X/aa693f. Fulltekst i vitenarkiv
• Hupfer, Alexander; Bhoodoo, Chidanand; Vines, Lasse & Svensson, Bengt Gunnar (2017). Formation and evolution of E3 centers in hydrothermally grown zinc oxide. Materials Science in Semiconductor Processing. ISSN 1369-8001. 69, s. 13–18. doi: 10.1016/j.mssp.2017.02.022. Fulltekst i vitenarkiv Vis sammendrag

  The formation and evolution of the prominent and so-called E3 center in ZnO has been studied by in-situ deep level transient spectroscopy measurements after on-line implantation of hydrogen (H) and deuterium (D) ions at sample temperatures of and . The formation of E3 is shown to involve migration and subsequent trapping of interstitial hydrogen (Hi), or deuterium, and starts to occur already below 200 K. The concentration of implantation-induced E3 centers is rather unstable and decreases gradually at temperatures around 300 K by an annealing process obeying first-order kinetics. The process exhibits an activation energy of and involves presumably trapping of migrating Hi's leading to passivation of the E3 centers. A kinetics model is presented showing good agreement with the experimental data and where the E3 center is assumed to be a complex between a Zn vacancy and three hydrogen atoms . Further, the concentration of E3 centers is found to decrease rapidly during annealing in forming gas ambient at room temperature and then to recover gradually during subsequent annealing in vacuum, indicating a defect ‘core’ of the E3 center able to accommodate more than one H atom.

• Hupfer, Alexander; Bhoodoo, Chidanand; Vines, Lasse & Svensson, Bengt Gunnar (2016). Formation and annihilation of E4 centers in ZnO: Influence of hydrogen. Journal of Applied Physics. ISSN 0021-8979. 119(18). doi: 10.1063/1.4948241. Fulltekst i vitenarkiv Vis sammendrag

  Hydrothermally grown n-type ZnO bulk samples have been implanted with protons and deuterium ions to fluences in the range of 8 × 1010 to 8 × 1011 cm−2. The implantations were performed at the temperature of 285 K, and the samples were then analyzed in-situ by deep level transient spectroscopy (DLTS) using a setup connected to the implanter beam line. The concentration of the so-called E4 center, having an apparent energy level at ∼0.57 eV below the conduction edge, is found to increase linearly with the ion fluence and the generation rate is proportional to the elastic energy deposition, as expected for a primary defect. Isothermal annealing of the E4 center at temperatures between 290 and 315 K reveals first-order kinetics with the activation energy of ∼0.6 eV. The annealing rate is strongly enhanced with increasing hydrogen fluence, and a model invoking migration of interstitial hydrogen and subsequent reaction with E4 exhibits close agreement with the experimental data. The rate of electron capture by E4 during the DLTS filling pulse depends on temperature, and it displays a thermal barrier of ∼0.15 eV. Most of these experimental results for E4 conform to the theoretically predicted properties of the oxygen vacancy (VO) and a tentative assignment of E4 to VO is made, corroborating previous suggestions in the literature. In particular, the 0.57 eV level is ascribed to the double donor state of VO. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.

• Arcadipane, E.; Sanz, R; Amiard, G.; Boninelli, S.; Impellizzeri, G & Privitera, V. [Vis alle 11 forfattere av denne artikkelen] (2016). Single-crystal TiO2 nanowires by seed assisted thermal oxidation of Ti foil: Synthesis and photocatalytic properties. RSC Advances. 6(60), s. 55490–55498. doi: 10.1039/c6ra09088e. Fulltekst i vitenarkiv Vis sammendrag

  TiO2 nanowires (NWs) can improve the advantageous photocatalytic properties of TiO2 by increasing the active surface area. Here we investigate the synthesis of TiO2 NWs by thermal oxidation, studying the role of temperature, annealing time, and gas flow rates. The optimal thermal growth conditions were found to be 800 °C for 4 h in a mixed gas flow of Ar and O2. Morphological and structural characterizations, carried out by scanning and transmission electron microscopy, and X-ray diffraction, indicated a TiO2 rutile monocrystalline structure of the nanowires. An in situ thermal growth analysis was performed by means of an environmental electron microscope, providing additional insights into the TiO2 NWs growth dynamics. The photocatalytic properties were studied by using the degradation rate of methylene blue under UV light. TiO2 NWs revealed a 70% improvement of the degradation rate compared to a reference TiO2 bulk sample. Moreover, NWs were additionally annealed in forming gas (5% H2 in N2) in order to promote the formation of oxygen vacancies and an increase of the carrier density. Indeed, the photocatalytic activity of the NWs treated in forming gas was 3 times higher than that of the reference TiO2 bulk sample. The photonic efficiency and the quantum efficiency, also showed an increase versus bulk TiO2 of about 20% in the presence of NWs, and of about 100% with the forming gas annealing. Moreover, this increase in the photocatalytic activity after the forming gas annealing also correlates with the disappearance of a deep level recombination center as observed by deep level transient spectroscopy.

• Bhoodoo, Chidanand; Hupfer, Alexander; Vines, Lasse; Monakhov, Edouard & Svensson, Bengt Gunnar (2016). Evolution kinetics of elementary point defects in ZnO implanted with low fluences of helium at cryogenic temperature. Physical Review B. Condensed Matter and Materials Physics. ISSN 1098-0121. 94(20). doi: 10.1103/PhysRevB.94.205204. Fulltekst i vitenarkiv Vis sammendrag

  © 2016 American Physical Society

• Hupfer, Alexander; Bhoodoo, Chidanand; Vines, Lasse & Svensson, Bengt Gunnar (2014). The E3 center in zinc oxide: Evidence for involvement of hydrogen. Applied Physics Letters. ISSN 0003-6951. 104(9). doi: 10.1063/1.4867908. Fulltekst i vitenarkiv

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• Hupfer, Alexander; Bhoodoo, Chidanand; Vines, Lasse & Svensson, Bengt Gunnar (2017). Formation and Evolution of E3 centers in Hydrothermally grown Zinc Oxide. Fulltekst i vitenarkiv
• Arcadipane, E; Sanz, R; Amiard, G; Boninelli, S; Impellizzeri, G & Privitera, V [Vis alle 11 forfattere av denne artikkelen] (2017). Correction: Single-crystal TiO2 nanowires by seed assisted thermal oxidation of Ti foil: synthesis and photocatalytic properties (RSC Adv. (2016) 6 (55490-55498) DOI: 10.1039/C6RA09088E. RSC Advances. 7(19), s. 11222–11222. doi: 10.1039/c7ra90019h. Fulltekst i vitenarkiv
• Hupfer, Alexander; Bhoodoo, Chidanand; Vines, Lasse & Svensson, Bengt Gunnar (2016). Formation and annihilation of E4 centers in ZnO: influence of hydrogen. Fulltekst i vitenarkiv
• Hupfer, Alexander; Bhoodoo, Chidanand; Persson, Clas; Vines, Lasse & Svensson, Bengt Gunnar (2016). Formation and evolution of E3 centers in hydrothermally grown zinc oxide. Fulltekst i vitenarkiv
• Bhoodoo, Chidanand; Hupfer, Alexander; Vines, Lasse; Monakhov, Edouard & Svensson, Bengt Gunnar (2016). Evolution Kinetics of Elementary Point Defects in ZnO Implanted with Low Fluences of Helium at Cryogenic Temperature. Fulltekst i vitenarkiv
• Bhoodoo, Chidanand; Hupfer, Alexander; Vines, Lasse; Monakhov, Edouard & Svensson, Bengt Gunnar (2014). Formation kinetics of a deep acceptor-like level in helium-implanted ZnO. Fulltekst i vitenarkiv
• Bhoodoo, Chidanand; Vines, Lasse; Monakhov, Edouard & Svensson, Bengt Gunnar (2014). Annealing Kinetics of The Single Vacancy in Silicon studied By Low Temperature Irradiation And Deep Level Transient Spectroscopy. Fulltekst i vitenarkiv
• Bhoodoo, Chidanand; Vines, Lasse; Monakhov, Edouard & Svensson, Bengt Gunnar (2013). Dopant concentration dependence of local compensation in low-dose ion-bombarded Silicon. Fulltekst i vitenarkiv
• Bhoodoo, Chidanand; Vines, Lasse; Monakhov, Edouard & Svensson, Bengt Gunnar (2013). Dopant concentration dependence of local compensation in low-dose ion-bombarded n-type Silicon. Fulltekst i vitenarkiv

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