Structure and optical properties of CuInSe₂ and Cu_0.9In_0.9Zn_0.2Se₂ thin films deposited by one-step radio-frequency magnetron sputtering

CuInSe₂ (CIS) and Cu_0.9In_0.9Zn_0.2Se₂ (CIZS) thin films were deposited by Radio-Frequency (RF) magnetron sputtering process. X-ray diffraction (XRD) results indicate CIZS film deposited at 300℃ (CIZS-300) is (220) preferred orientation which is different from (112) preferred orientation of other films. Cu-poor and appropriate temperature are major factors for (220) preferred orientation of grains. The Raman spectra show a strong peak around 171 cm^-1 and a weak peak around 206 cm^-1, which corresponding to A₁ and B₂ modes. Substitution of Zn for Cu leads to a broadening and blue-shift of A₁ Raman mode. The band gap E_opt of CIZS film increases due to a reduced Se p-Cu d interband repulsion with Zn doping. Scanning electron microscope (SEM) measurement demonstrates that the surface morphology of CIZS is more compact and smoother than that of CIS thin films.