Atomic-Scale Mechanisms of MoS₂ Oxidation\nfor Kinetic Control of MoS₂/MoO₃ Interfaces

Abstract

Oxidation of transition metal dichalcogenides\n(TMDs) occurs readily\nunder a variety of conditions. Therefore, understanding the oxidation\nprocesses is necessary for successful TMD handling and device fabrication.\nHere, we investigate atomic-scale oxidation mechanisms of the most\nwidely studied TMD, MoS₂. We find that thermal oxidation\nresults in α-phase crystalline MoO₃ with sharp interfaces,\nvoids, and crystallographic alignment with the underlying MoS₂. Experiments with remote substrates prove that thermal oxidation\nproceeds via vapor-phase mass transport and redeposition, a challenge\nto forming thin, conformal films. Oxygen plasma accelerates the kinetics\nof oxidation relative to the kinetics of mass transport, forming smooth\nand conformal oxides. The resulting amorphous MoO₃ can\nbe grown with subnanometer to several-nanometer thickness, and we\ncalibrate the oxidation rate for different instruments and process\nparameters. Our results provide quantitative guidance for managing\nboth the atomic scale structure and thin-film morphology of oxides\nin the design and processing of TMD devices.