The role of Nitrogen during selenization in enhancing CZTS thin film properties

Abstract

The kesterite (Cu₂ZnSn(SSe)₄) thin film’s material properties strongly depend on the annealing parameters. The formation of good property kesterite films requires annealing at high temperatures. The properties of the CZTSe films are impacted by changes in the annealing parameters. The two most important annealing parameters are the annealing temperature profile and the annealing environment. The characteristics of the film are impacted by variations in the annealing atmosphere. In order to study the impact of the annealing environment on the CZTSe compound semiconductor, each element of CZTSe was deposited using the thermal deposition technique in a sequence of CuSn, Zn, Se, followed by the annealing process. In the current study, the films were annealed at the same temperature in both the Se and Se + N₂ atmospheric conditions to produce the CZTSe compound. The annealing was done in a two-step process. Films were first annealed for 10 min at 230 °C, followed by 10 min at 450 °C. Two different sets of films were fabricated. The paper describes in detail the impact of annealing atmospheres of Se + N₂ and Se on the unit cell structure and other characteristics of the CZTSe thin film. It was shown that the CZTS film annealed in Se + N₂ atmosphere has improved properties.