Electrical and optical properties of Cu2ZnSnS4 thin films prepared by rf magnetron sputtering process

Cu2ZnSnS4 thin films were deposited on corning 7059 glass substrates without substrates heating by rf magnetron sputtering. The Cu/(Zn+Sn) ratio of the thin film sputtered at 75 W was close to the stoichiometry of Cu2ZnSnS4. However, the S/(Cu+Zn+Sn) ratio was less than the stoichiometry. The as-deposited films were amorphous and annealed in the atmosphere of Ar+S2 (g). The annealed (1 1 2), (2 0 0), (2 2 0), (3 1 2) planes were conformed to all the reflection of a kesterite structure. A preferred (1 1 2) orientation was observed with the increase of the annealing temperature. The optical absorption coefficient of the thin film was about 1.0×104 cm−1. The optical band energy was derived to be 1.51 eV. The optical absorption coefficient of the sputtered Cu2ZnSnS4 thin films was less than that of CuInS2 thin film, however, the band gap energy was more appropriate for photovoltaic materials.