For Si NPs, similar sublimation and oxidative etching kinetic experiments were reported. Si also etched and sublimed, but the kinetics depended strongly upon both TNP and oxygen pressure (PO2). At low TNP, sublimation was slow, and oxidation led to substantial (up to ~70%) mass loss, with eventual passivation, where EEO2 dropped several orders of magnitude. The etching and passivation kinetics were modeled, and in general the NP etching mechanism was consistent with that proposed for bulk Si(100) etching. To account for the eventual passivation, under conditions where passivation is not observed for bulk Si, the model included O diffusion from surface to subsurface sites, with eventual subsurface saturation triggering passivation of the surface. One motivation of the current experiments was to examine the effects of higher initial subsurface oxygen content on the etching and passivation behavior for Si-rich NPs.