Heteroepitaxial growth of CZTS

A summary of preparation methods of various substrates suitable for the epitaxial growth of copper zinc tin sulfide (CZTS) via molecular beam epitaxy (MBE) is presented. Substrates evaluated include silicon (various orientations), ZnS(110), Al₂O₃(0001), and gallium phosphide (GaP) (100). An overview of the techniques used to prepare a high-quality, epi-ready surface for each substrate is covered, with special attention given to the limitations presented by CZTS MBE, namely the stability of surfaces with respect to sulfur vapor. The quality of the substrates prior to growth has been assessed by in-situ reflection high-energy electron diffraction (RHEED) and photoemission techniques. ZnS epitaxial growth was attempted on all substrates because ZnS is viewed as a simplified model system for CZTS. ZnS epitaxial quality was assessed using RHEED during growth and via electron backscatter diffraction (EBSD) post-growth.