Measurements of absolute Cu, Zn and Sn metastable densities in CZTS sputtering plasmas measured using UVAS technique

In the present study, absolute density of Cu, Zn, and Sn metastable in the discharge phase of magnetron sputtering plasma were evaluated experimentally. Magnetron sputtering plasma system using stoichiometric Cu2ZnSnS4 compound target was produced with pulsed-modulated rf 13.56 MHz power supply. Then, the temporal evolution of atomic metastable density in the afterglow was measured using ultraviolet absorption spectroscopy techniques with hollow cathode lamp (HCL) as light source. The absorption signal decreased very rapidly after the termination of discharge power, indicating that the metastable density decreased rapidly in the afterglow. Therefore, the absolute Cu, Zn, and Sn metastable atom densities in the discharge phase were evaluated just after the termination of rf power. It has been observed that the absolute Cu, Zn, and Sn metastable atom densities in the gas phase were not in agreement with the stoichiometric composition of sputter target and deposited films. In addition, the characteristic of metastable atom densities was consistent with the ground state atom densities. The results suggest a possibility of unconventional sputtering process for compound sputter deposition.