Phase-Centric MOCVD Enabled Synthetic Approaches for Wafer-Scale 2D Tin Selenides

Abstract

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. A set of synthetic strategies is hereby presented to selectively produce wafer-scale tin selenides, SnSex (both x = 1 and 2), in the 2D forms. The 2D-SnSe2 films with tuneable thicknesses are directly grown via metal-organic chemical vapor deposition (MOCVD) at 200 degrees 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, which intrinsically inhibited from 2D growth, is indirectly prepared by a thermally driven phase transition of an as-grown 2D-SnSe2 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. These tailor-made synthetic routes will accelerate the low-thermal-budget production of multiphase 2D materials in a reliable and scalable fashion. With phase-tailored synthetic strategies, wafer-scale production of tin selenides in the 2D limit is achieved via a low-temperature metal-organic chemical vapor deposition (MOCVD) process. Directly grown 2D-SnSe2 exhibits outstanding crystallinity and tunable thickness, and SnSe, which has intrinsic limitations for 2D film growth, can be prepared via a phase transition, thereby retaining all of the advantages in the MOCVD-grown product. image