A Two-Step Magnetron Sputtering Approach for the Synthesis of Cu₂ZnSnS₄ Films from Cu₂SnS₃\ZnS Stacks

Cu₂ZnSnS₄ (CZTS) is regarded as one of the emerging materials for next-generation thin film solar cells. However, its synthesis is complex, and obtaining a single-phase CZTS thin film is difficult. This work reports the elaboration of Cu₂ZnSnS₄ thin films by a sequential magnetron sputtering deposition of Cu₂SnS₃ (CTS) and ZnS as stacked films. Initially, the CTS films were prepared on a soda lime glass substrate by annealing Cu and SnS₂ stacked layers. Second, ZnS was deposited by magnetron sputtering on the CTS films. The CTS\ZnS stacks were then annealed in Sn + S or S atmospheres. The tetragonal CZTS structure was obtained and confirmed by grazing incidence X-ray diffraction and Raman spectroscopy. The morphological and compositional characteristics, measured by scanning electron microscopy and energy-dispersive spectroscopy, revealed large grains and dense surfaces with the elemental composition close to the intended stoichiometry. Additional X-ray photoemission spectroscopy measurements were performed to determine the surface chemistry and particularities of the obtained films. The optical properties, determined using conventional spectroscopy, showed optimal absorber layer band gap values ranging between 1.38 and 1.50 eV. The electrical measurements showed that all the films are p-type with high carrier concentrations in the range of 10¹⁵ to 10²⁰ cm^-3. This new synthesis route for CZTS opens the way to obtain high-quality films by an industry-compatible method.