| Title |
Optical Properties of Cdlnsub 2Ssub 4 and Cdlnsub 2Ssub 4 : CdIn_2S_4 및 CdIn_2S_4 : Co^{2+}Single Crystals |
| Authors |
최성휴(Choe, Seong-Hyu) ; 방태환(Bang, Tae-Hwan) ; 김형곤(Kim, Hyeong-Gon) |
| Keywords |
CdIn_2S_4 ; CdIn_2S_4 : Co^{2+} single crystals ; Crystal structure ; Optical energy gap ; Impurity optical absorption ; Electronic transition ; Tsub d symmetry site of Cdlnsub 2Ssub 4 host lattece |
| Abstract |
CdIn_2S_4 and CdIn_2S_4 : Co^{2+} singlecrystals of thenormal spinel structure were grown by the C.T.R. method. The optical energy band structure of these compounds had a indirect band gap at the fundamental optical absorption band edge. The direct and the indirect energy gaps are found to be 2.325 and2.179eV for Cdln_2S_4 , and 2.303 and 2.169eV for CdIn_2S_4 and CdIn_2S_4 : Co^{2+} at 5K, respectivly. The fundamental absorption band edge of these single crystals shift to a shorter wavelength region with decreasing temperature, and the temperature dependence of the optical energy gaps in these compounds satisfy Varshni equation. The Varshni constantsα and β of the direct energy gap are given by 13.39×10_{-4}eV/K and 509 K for Cdln_2S_4 and 29.73×10_{-4} eV/K and 1398K for CdIn_2S_4 and CdIn_2S_4 : Co^{2+}. The Varshni constants {α}and {β} of the indirect energy gap are given by 9.68×10^{-4} eV/K 308K for Cdln_2S_4 and 13.33×10_{-4}eV/K and 440K for CdIn_2S_4 : Co^{2+} respectivly. The impurity optical absorption peaks due to cobalt dopant are observed in CdIn_2S_4 : Co^{2+} single crystal. These impurity optical absorption peaks can be attributed to the electronic transitions between the split energy levels of Co_{2+} ions located at T_d symmetry site of Cdln_2S_4 host lattece. |