Phase-centric MOCVD Enabled Synthetic Approaches for Wafer-scale 2D Tin Selenides.

Following an initial nucleation stage at the flake level, atomically thin film growth of a van der Waals material is promoted by ultrafast lateral growth and prohibited vertical growth. To produce these highly anisotropic films, synthetic or post-synthetic modifications are required, or even a combination of both, to ensure large-area, pure-phase and low-temperature deposition. We hereby present a set of synthetic strategies to selectively produce wafer-scale tin selenides, SnSe x (both x = 1 and 2), in the two-dimensional (2D) forms. The 2D-SnSe 2 films with tuneable thicknesses are directly grown via metal-organic chemical vapor deposition (MOCVD) at 200 °C, and they exhibit outstanding crystallinities and phase homogeneities and consistent film thickness across the entire wafer. This is enabled by excellent control of the volatile metal-organic precursors and decoupled dual temperature regimes for high-temperature ligand cracking and low-temperature growth. In contrast, SnSe, intrinsically inhibited from 2D growth, is indirectly prepared by a thermally driven phase transition of an as-grown 2D-SnSe 2 film with all the benefits of the MOCVD technique. It is accompanied by the electronic n-type to p-type crossover at the wafer scale. Our tailor-made synthetic routes will accelerate the low-thermal-budget production of multiphase 2D materials in a reliable and scalable fashion. This article is protected by copyright. All rights reserved.