Controlled Growth of Large-Area Bilayer Tungsten Diselenides with Lateral P-N Junctions.

Mandyam, Srinivas V; Zhao, Meng-Qiang; Masih Das, Paul; Zhang, Qicheng; Price, Christopher C; Gao, Zhaoli; Shenoy, Vivek B; Drndić, Marija et al. · ACS Nano · 2019

basic_science · Level V

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Abstract

Bilayer two-dimensional (2D) van der Waals (vdW) materials are attracting increasing attention due to their predicted high quality electronic and optical properties. Here, we demonstrate dense, selective growth of WSe<sub>2</sub> bilayer flakes by chemical vapor deposition with the use of a 1:10 molar mixture of sodium cholate and sodium chloride as the growth promoter to control the local diffusion of W-containing species. A large fraction of the bilayer WSe<sub>2</sub> flakes showed a 0 (AB) and 60° (AA') twist between the two layers, whereas Moiré 15 and 30° twist angles were also observed. Well-defined monolayer-bilayer junctions were formed in the as-grown bilayer WSe<sub>2</sub> flakes, and these interfaces exhibited <i>p-n</i> diode rectification and an ambipolar transport characteristic. This work provides an efficient method for the layer-controlled growth of 2D materials, in particular, 2D transition metal dichalcogenides, and promotes their applications in next-generation electronic and optoelectronic devices.