  Understanding oxidation mechanisms of layered semiconducting transition-metal
dichalcogenide (TMDC) is important not only for controlling native oxide
formation but also for synthesis of oxide and oxysulfide products. Here,
reactive molecular dynamics simulations show that oxygen partial pressure
controls not only the ZrS2 oxidation rate but also the oxide morphology and
quality. We find a transition from layer-by-layer oxidation to
amorphous-oxide-mediated continuous oxidation as the oxidation progresses,
where different pressures selectively expose different oxidation stages within
a given time window. While the kinetics of the fast continuous oxidation stage
is well described by the conventional Deal-Grove model, the layer-by-layer
oxidation stage is dictated by reactive bond-switching mechanisms. This work
provides atomistic details and a potential foundation for rational
pressure-controlled oxidation of broad TMDC materials.
