Growth Kinetics and Atomistic Mechanisms of Native Oxidation of ZrS_<i>x</i>Se_2–<i>x</i> and MoS₂ Crystals

Abstract

A thorough understanding of native oxides is essential for designing semiconductor devices. Here, we report a study of the rate and mechanisms of spontaneous oxidation of bulk single crystals of ZrS_<i>x</i>Se_2-<i>x</i> alloys and MoS₂. ZrS_<i>x</i>Se_2-<i>x</i> alloys oxidize rapidly, and the oxidation rate increases with Se content. Oxidation of basal surfaces is initiated by favorable O₂ adsorption and proceeds by a mechanism of Zr-O bond switching, that collapses the van der Waals gaps, and is facilitated by progressive redox transitions of the chalcogen. The rate-limiting process is the formation and out-diffusion of SO₂. In contrast, MoS₂ basal surfaces are stable due to unfavorable oxygen adsorption. Our results provide insight and quantitative guidance for designing and processing semiconductor devices based on ZrS_<i>x</i>Se_2-<i>x</i> and MoS₂ and identify the atomistic-scale mechanisms of bonding and phase transformations in layered materials with competing anions.