Sticking probabilities of Cu, Zn, Sn, and S atoms in magnetron sputtering plasmas employing a Cu2ZnSnS4 stoichiometric target

Investigations on the density decays in the afterglow of pulsed magnetron sputtering plasmas employing a Cu2ZnSnS4 (CZTS) stoichiometric target were performed to evaluate the sticking probabilities of Cu, Zn, Sn and S atoms. The sticking probabilities were evaluated from the linear relationships between the decay time constants of the atom densities and the discharge pressure. It has been found that the sticking probabilities of Cu, Zn, and Sn are almost the same. On the other hand, the sticking probability of S atom was found to be as low as 0.7 ± 0.1, if we assume unity for the sticking probabilities of Cu, Zn, and Sn. Therefore, it has been shown that the less-abundant composition of S atoms in sputter-deposited CZTS thin films is attributed to the small sticking probability of S.