The Effects of Substrate Temperature on the Properties of Kesterite Cu2ZnSnS4 Thin Films Deposited Using a Single Quaternary Target

Abstract

Thin films of kesterite Cu2ZnSnS4 (CZTS) were fabricated at various substrate temperatures from 200 to 500 degrees C using a single quaternary target. Film fabrication was completed after a sulfurization post annealing process in an atmosphere containing sulfur (H2S (5%)+ N-2, mixture gas). Films deposited at different substrate temperatures were characterized, and then an optimized temperature was chosen. An excessively Sn-rich film was obtained at high substrate temperatures, and unheated substrates showed compositions that approached stoichiometric values of Cu2ZnSnS4. X-ray diffraction analysis and Raman spectroscopy were used to investigate the appearance and disappearance of Cu-based and Sn-based secondary phases as a function of substrate temperature. The properties of the films were found to be directly related to the substrate temperature. We observed that Zn and Sn compositions steadily decreased with increasing temperature. The critical temperature that determines secondary phases and composition was found to be between 300 degrees C and 400 degrees C. We also discussed methods of achieving high quality Cu2ZnSnS4 kesterite films with good compositions.