Optical properties of Co 0.2Ga 2S 3.2 single crystals

Abstract

Co 0.2Ga 2S 3.2 single crystals were prepared by a chemical tranport method. The optical energy gap of this single crystal was 2.578 eV at 150 K, the optical absorption peaks due to the transition 4A 2( 4F)→ 4T 1( 4P) , 4A 2( 4F)→ 4T 1( 4F) , and 4A 2( 4F)→ 4T 2( 4F) of Co 2+ entered the substitutional tetrahedral site appeared at 13333, 6557 and 4395 cm -1 at room temperature, and Racah parameters were given by Dq=439cm -1, B=447cm -1. The impurity photoconductivity peaks at 150 K were observed at 2.032, 1.758 and 1.653eV and these are attributed to the transitions between the band edge of Co 0.2Ga 2S 3.2 single crystal and the 4 T 2( 4 F), 4 T 1( 4 F) and 4 T 1( 4 P) electronic energy levels of Co 2+ ion.