Atomic-Scale Mechanisms of MoS<sub>2</sub>Oxidation for Kinetic Control of MoS<sub>2</sub>/MoO<sub>3</sub>Interfaces
Kate Reidy, Wouter Mortelmans, Seong Soon Jo, Aubrey Penn, Alexandre C. Foucher, Zhenjing Liu, Tao Cai, Baoming Wang, Frances M. Ross, R. Jaramillo
Abstract
Oxidation of transition metal dichalcogenides (TMDs) occurs readily under a variety of conditions. Therefore, understanding the oxidation processes is necessary for successful TMD handling and device fabrication. Here, we investigate atomic-scale oxidation mechanisms of the most widely studied TMD, MoS 2 . We find that thermal oxidation results in α-phase crystalline MoO 3 with sharp interfaces, voids, and crystallographic alignment with the underlying MoS 2 . Experiments with remote substrates prove that thermal oxidation proceeds via vapor-phase mass transport and redeposition, a challenge to forming thin, conformal films. Oxygen plasma accelerates the kinetics of oxidation relative to the kinetics of mass transport, forming smooth and conformal oxides. The resulting amorphous MoO 3 can be grown with subnanometer to several-nanometer thickness, and we calibrate the oxidation rate for different instruments and process parameters. Our results provide quantitative guidance for managing both the atomic scale structure and thin-film morphology of oxides in the design and processing of TMD devices.