Epitaxial Semiconducting Cu₂Se Nanosheets on Cu(111) Substrates Using Direct Deep Selenization

Previous studies have reported that reactions between selenium (Se) and metal substrates can lead to the formation of monolayer materials, but no studies have reported on the thickness that can be achieved for ordered films formed by this method. Here, we report that 2D layered Cu 2 Se can be successfully fabricated on the Cu(111) surface through Se deposition at room temperature using molecular beam epitaxy (MBE). Using aberration-corrected scanning transmission electron microscopy (STEM), we obtained the first cross-sectional STEM image with atomic resolution. This image serves as direct evidence supporting the validity of the theoretical model for layered Cu 2 Se. Our findings demonstrate that the ordered structure can achieve a thickness of approximately 38 nm under room temperature conditions, altering the prevailing perception of the formation of monolayer or few-layer structures through the reaction between Se and Cu(111) substrate. Our work provides valuable insights for the synthesis of layered Cu 2 Se with specific thicknesses, a novel two-dimensional semiconductor material, which holds potential applications in future electronic devices.