Chemical vapor deposition growth of monolayer MoSe2 nanosheets

Abstract

The synthesis of two-dimensional (2D) layered materials with controllable thickness is of considerable interest for diverse applications. Here we report the first chemical vapor deposition growth of single- and few-layer MoSe 2 nanosheets. By using Se and MoO 3 as the chemical vapor supply, we demonstrate that highly crystalline MoSe 2 can be directly grown on the 300 nm SiO 2 /Si substrates to form optically distinguishable single- and multi-layer nanosheets, typically in triangular shaped domains with edge lengths around 30 μm, which can merge into continuous thin films upon further growth. Micro-Raman spectroscopy and imaging was used to probe the thickness-dependent vibrational properties. Photoluminescence spectroscopy demonstrates that MoSe 2 monolayers exhibit strong near band edge emission at 1.55 eV, while bilayers or multi-layers exhibit much weaker emission, indicating of the transition to a direct band gap semiconductor as the thickness is reduced to a monolayer.