Low-temperature surface preparation and epitaxial growth of ZnS and Cu2ZnSnS4 on ZnS(1 1 0) and GaP(1 0 0)

Abstract

We give a summary of the low-temperature preparation methods of ZnS(110) and GaP(100) crystals for epitaxial growth of ZnS and Cu2ZnSnS4 (CZTS) via molecular beam epitaxy. Substrates were prepared for epitaxial growth by means of room-temperature aqueous surface treatments and subsequent ultra-high vacuum transfer to the deposition system. Epitaxial growth of ZnS was successful at 500K on both ZnS(110) and GaP(100) as only single domains were observed with electron backscatter diffraction; furthermore, transmission electron microscopy measurements confirmed an epitaxial interface. Epitaxial growth of CZTS was successful on ZnS at 700K. However, epitaxial growth was not possible on GaP at 700K due to GaxSy formation, which significantly degraded the quality of the GaP crystal surface. Although CZTS was grown epitaxially on ZnS, growth of multiple crystallographic domains remains a problem that could inherently limit the viability of epitaxial CZTS for model system studies.