Epitaxial growth of ZrSe2 nanosheets on sapphire via chemical vapor deposition for optoelectronic application

Abstract

Group IVB (Zr and Hf) transition metal dichalcogenides (TMDs) have attracted considerable attention due to their predicted excellent electronic properties that are superior to group VIB TMDs. However, the synthesis of high-quality ZrSe₂ layers is seldom reported, greatly hindering the development of this new field. Herein, the epitaxial growth of ZrSe₂ on c-plane sapphire substrates is, for the first time, demonstrated using the low-pressure chemical vapor deposition (CVD) method. Impressively, the CVD-grown high-quality ZrSe₂ layers exhibit an atomically sharp interface with the underlying substrate, and their epitaxial relationship is determined to be: ZrSe₂ (0001)[10–10]||Al₂O₃ (0001)[11–20]. The electronic band structures of ZrSe₂ are calculated using density functional theory methods, showing an indirect band gap of 1.19 eV and a minimum direct band gap of 1.79 eV, respectively. The band gap of ZrSe₂ layers is also determined from the UV-visible absorption spectra, which is in good agreement with our band-structure calculations. Furthermore, a photodetector was fabricated based on the CVD-grown ZrSe₂ layer on a sapphire substrate, which exhibits a stable and appreciable photoresponse for visible light.