Structure and bandgap evolution of chromium selenide epitaxially grown on Au(111): From CrSe2 to Cr2Se3

Two-dimensional (2D) chromium selenide with different stoichiometries have attracted considerable interest because of their exotic electronic and magnetic properties. Herein, the monolayer CrSe2 on the Au(111) substrate was synthesized by molecular beam epitaxy and annealed to form monolayer Cr2Se3, which was revealed by the scanning tunneling microscopy. Moir & eacute; superstructure in CrSe2/Au(111) was observed with a twist angle of similar to 1.5 degrees, and the stacking position-dependent p-type semiconducting characteristic of CrSe2 on Au(111) was recorded by scanning tunneling spectroscopy. Due to the annealing induced strong interfacial interaction, structural and electronic properties transited from CrSe2 to Cr2Se3, with the latter exhibiting metallic feature. Correspondingly, the original Se-8 molecules surrounding CrSe2 assembled into root 3 x root 3 R30 degrees-Se/Au reconstruction, which further verified the structural transition. Our work provides a basis for fundamental study of stoichiometric-dependent physics and potential applications in data storage devices.