Large-scale synthesis of WSe2 atomic layers on SiO2/Si

Abstract

We report a systematic study of large-scale growth of high-quality WSe2 atomic layers directly on SiO2/Si substrates using a convenient method. Various parameters, especially growth temperatures, flow rate of carrier gas and tube pressure, are investigated in affecting the properties of as-grown WSe2 flakes in terms of their sizes, shapes and thickness. The pre-annealing step is demonstrated to be a key role in achieving the large-scale growth. Under an optimized condition, the lateral size of triangular single-crystal monolayer WSe2 is up to 30 [Formula: see text]m and the area of the monolayer thin film can be up to 0.25 mm2. And some other interesting features, such as nanoflowers, are observed, which are a promising for catalyzing research. Raman spectrum and microphotoluminescence indicate distinct layer dependent efficiency. Auger electron spectroscopy (AES) studies demonstrate the atomic concentration of the as-grown WSe2. Electrical transport further shows that the [Formula: see text]-type WSe2 field-effect transistors exhibit excellent electrical properties with carrier mobility of [Formula: see text][Formula: see text]64 cm[Formula: see text]V[Formula: see text]s[Formula: see text] and current on/off ratio over 105. These results are comparable to the exfoliated materials.