Optical and surface probe investigation of secondary phases in Cu2ZnSnS4 films grown by electrochemical deposition

Cu2ZnSnS4 (CZTS) films were grown by electrochemical deposition, and we measured the work function of the as-grown and of the KCN-etched CZTS surfaces by using Kelvin probe force microscopy (KPFM) and micro-Raman scattering spectroscopy with incident laser wavelengths of 488.0 and 632.8 nm, respectively, and the results indicate that a secondary phase formed at different depths. The KPFM measurements can discriminate phase uniformity at the nano-scale. Secondary phases, such as Cu2−xS (0