Structural evolution of multilayer SnS/Cu/ZnS stack to phase-pure Cu2ZnSnS4 thin films by thermal processing

Abstract

In this work, thin films of phase-pure Cu2ZnSnS4 (CZTS) were developed from a stack of binary metal sulfides by post-deposition thermal processing. The precursor stack SnS/Cu/ZnS was grown by sequential electrodeposition of SnS and Cu layers followed by thermal evaporation of ZnS layer. The transformation from binary/ternary composition to phase-pureCZTSwas studied using different experimental tools such asX-ray diffraction (XRD),Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The TEM images revealed the formation of tetragonal crystals with interplanar spacing 0.312 nm. Raman spectra of the films confirmed that annealing at 550.C for 30 min under N2/S ambient resulted in the formation of phase-pure CZTS film. The bandgap estimated from the optical transmittance and reflectance spectra showed a direct transition at 1.59 eV. The films are photosensitive and the photo electrochemical measurements showed the p-type conductivity of the films. � The Author(s) 2015. Published by ECS.