Process Control of Atomic Layer Deposition Molybdenum Oxide Nucleation and Sulfidation to Large-Area MoS2 Monolayers

Recent advances in the field of two-dimensional (2D) transition metal dichalcogenide (TMD) materials have indicated that atomic layer deposition (ALD) of the metal oxide and subsequent sulfidation could offer a method for the synthesis of large area two-dimensional materials such as MoS2 with excellent layer control over the entire substrate. However, growing large area oxide films by ALD with sub 1 nm nucleation coalescence remains a significant challenge, and the necessary steps are unexplored. In this work, we demonstrate the necessary process improvements required to achieve sub 1 nm nucleation control by characterization of nucleation domains formed by oxide deposition. Synthesis of the TMD MoS2 from sulfidation of oxide deposited by both thermal ALD from (tBuN)2(NMe2)2Mo and O3 and plasma enhanced ALD (PEALD) from (tBuN)2(NMe2)2Mo and remote O2 plasma was performed. Large uniform MoS2 areas were achieved by optimizing the effects of various growth process conditions and surface treatments on the ALD...