Growth and optical properties of undoped and Co-doped CdS single crystals

CdS 및 $CdS:Co^{2+}$ 단결정의 성장과 광학적 특성

CdS and $CdS:Co^{2+}$ single crystals were grown by CTR method using iodine as transport material. The grown single crystals have defect chalcopyrite structure with direct band gap. The optical energy band gap was decreased according to add of Co-impurity. We can observed the Co-impurity optical absorption peaks assigned to the $Co^{2+}$ ion sited at the $T_d$ symmetry lattice and we consider that they were attributed to the electron transitions between energy levels of ions.