Influence of annealing temperature on structural and optical properties of Cu₂MnSnS₄ thin films fabricated by sol-gel technique

Cu₂MnSnS₄ (CMTS) thin films are synthesized by sol-gel technique and the influence of post-annealing temperatures on the composition, morphology, structure and optical properties have been investigated. X-ray diffraction and Raman measurements reveal the formation of polycrystalline CMTS thin films, where the crystalline degree increases and compressive strain relaxes with increasing the annealing temperature. Synthesis at the best process temperature of 580 °C give a pure CMTS crystal phase, whereas secondary phases are formed at reaction temperature lower than 540 °C, and the films decomposed severely at annealing temperature higher than 600 °C. The morphological and chemical composition studies indicate the formation of compact and homogeneous CMTS thin films with slightly S-poor condition. Further optical transmission spectra reveal that the band gaps of CMTS thin films is tuned in the range of 1.62-1.14 eV by adjusting the post-annealing temperature.