Lookup NU author(s): Professor Patrick Briddon
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The features of the VO2 centers formation in Si1-xGex using FTIR spectroscopy and ab initio modelling were studied. It has been found that VO2 vibrational mode gradually shifts towards the low frequencies with the increasing Ge content and possesses a well-defined structure. The fitting of VO2 absorption band with a sum of Gaussians has shown that VO2 absorption band consists of three components with intensities rising with increasing Ge content. The observed complicated structure of the VO2 absorption band is supposed to appear owing to the different combinations of VO2 and neighboring Si and Ge atoms. Density-functional calculations show that the formation of a Ge-O bond in VO2 costs at least 0.5 eV in excess to the formation of an Si-O bond. The averaged frequency shift, taken from several randomly generated Si123Ge4O2 supercells, is of the same order of magnitude as that of the experimental data for x = 0.035. Defects with high formation energy involving Ge-O-Si and Ge-O-Ge units produce frequencies not seen experimentally. When a Ge atom perturbs VO2 in silicon, it is found that Si-O bonds are favored by 0.5 eV than Ge-O bonds. The lowest energetic configuration is when Ge is a first nearest neighbor of the SiO2 quasi-molecule, lying on the same plane. These configurations produce the highest upward LVM shift and may account for the appearance of the two extra bands in the higher frequency side for x = 0.035. © 2006 Elsevier Ltd. All rights reserved.
Author(s): Khirunenko LI, Pomozov YuV, Sosnin MG, Trypachko MO, Torres VJB, Coutinho J, Jones R, Briddon PR, Abrosimov NV, Riemann H
Editor(s): Claeys, C; Peaker, T; Svensson, B; Vanhellemont, J
Publication type: Conference Proceedings (inc. Abstract)
Publication status: Published
Conference Name: European MRS 2006 Spring Meeting
Year of Conference: 2006
Publisher: Materials Science in Semiconductor Processing: Pergamon
Notes: Symposium T: Germanium based semiconductors from materials to devices