Siam Physics Congress 2015

IR spectroscopy of O-related defects in CdSe

21 May 2015, 08:00

3h

Board: CON-10

Poster presentation Condensed Matter Physics Poster-2

Speaker

Ms Pimpika Pimsorn (School of Physics and NANOTEC-SUT Center of Excellence on Advanced Functional Nanomaterials, Suranaree University of Technology, 111 University Avenue, Muang District, Nakhon Ratchasima, 30000 Thailand; Synchrotron Light Research Institute, 111 University Avenue, Muang District, Nakhon Ratchasima, 30000 Thailand; Thailand Center of Excellence in Physics (ThEP Center), Commission on Higher Education, Bangkok 10400, Thailand)

Description

Detailed infrared (IR) absorption spectroscopy of O$_2$-related defects in zincblend-CdTe and wurtzite-CdSe were reported by Lavrov *et al* [Phys. Rev. B **84**, 233201 (2011), AIP conf. Proc. **1583**, 169 (2014)]. They clearly showed based on their experimental work that the IR absorption bands at 1096.8 and 1108.4 cm$^{-1}$ in CdTe samples are associated with the vibrational modes of SO$_2$-related defects in CdTe. In wurtzite-CdSe, due to the reduction in the symmetry (in comparison to the zincblende structure), there are three absorption peaks at 1094.2, 1107.5, and 1126.3 cm$^{-1}$ related to the SO$_2$ defects, instead of two. T-Thienprasert *et al* [J. Appl. Phys. **115**, 203511 (2014)] recently showed that SO$_2$ in CdTe can form a complex defect with Cd vacancy becoming SO$_2$-V$_\mathrm{Cd}$ complex defects with the vibrational frequencies in good agreement with the values observed by Lavrov *et al*. In this work, we employed first-principles calculations to study the SO$_2$-related defects in wurtzite-CdSe. Their formation energies were calculated and used to analyze the stable ones. The vibrational frequency associated with each defect were calculated via the frozen-phonon approximation and used to compare with the observed values. In wurtzite-CdSe, We found that the SO$_2$ defects can bind with V$_\mathrm{Cd}$ becoming SO$_2$-V$_\mathrm{Cd}$ complex defects similar to the case of SO$_2$ in CdTe. However, due to the lower symmetry of wurtzite structure, there are many possible orientations of SO$_2$-V$_\mathrm{Cd}$ complex defects, which will be presented along with their formation energies as well as calculated vibrational frequencies.