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

TL;DR

This paper presents a controlled chemical vapor deposition method for growing large-area bilayer WSe2 with well-defined p-n junctions, enabling advanced electronic and optoelectronic applications.

Contribution

It introduces a novel growth technique using a specific promoter mixture to achieve layer-controlled bilayer WSe2 with distinct twist angles and junction properties.

Findings

Successful dense growth of bilayer WSe2 with controlled twist angles.

Formation of monolayer-bilayer junctions exhibiting diode rectification.

Method enhances potential for 2D material-based electronic devices.

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 WSe2 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 WSe2 flakes showed a 0 and 60o twist between the two layers, while moire 15 and 30o-twist angles were also observed. Well-defined monolayer-bilayer junctions were formed in the as-grown bilayer WSe2 flakes, and these interfaces exhibited p-n 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.