Epitaxial growth of wafer-scale two-dimensional polytypic ZnS thin films on ZnO substrates

摘要

In this paper, we report the first successful epitaxial synthesis of flat wafer-scale two-dimensional ZnS thin films on singlecrystalline ZnO substrates with high reproducibility, stability, and reliability, despite the large lattice mismatch (approximately 20%) between ZnO and ZnS. The as-grown ZnS was composed of two crystal phases: wurtzite (WZ) and zinc blende (ZB). The epitaxial orientation between the different phases was identified as: [2−1−10] ZnO//[2−1−10] ZnS//[10−1] ZnS and (0001) ZnO// (0001) ZnS//(111) ZnS. The crystal structure and the strain profile at the interfaces were studied in detail. After a simple etching treatment, exfoliated large-area free-standing ZnS thin films were achieved for the first time. The present product is expected to become valuable to the strategy of growing large-area thin films or heterostructures with a large lattice mismatch.