First principles study on the oxidation resistance of two-dimensional intrinsic and defective GeO2
Abstract
Although two-dimensional (2D) oxide semiconductors exhibit remarkable oxidation resistance compared to conventional 2D materials, the microscopic physical processes that govern this behavior at the atomic scale remains elusive. Using first-principles calculations, we investigated the defect formation and oxidation dynamics of the GeO2 monolayer (ML). The investigations reveal that the intrinsic GeO2 ML is resistant to oxidation due to strong electrostatic repulsion between surface oxygen ions and approaching O2 molecules, effectively suppressing chemisorption. In contrast, defective GeO2 ML with surface O vacancies shows vulnerability to oxidation with the O2 molecule occupying the vacancy through a low-energy activation energy (Ea) of 0.375 eV. Remarkably, the subsequent O2 dissociation into atomic species faces a higher activation barrier (Ea = 1.604 eV), suggesting self-limiting oxidation behavior. Electronic structure analysis demonstrates that oxidation primarily modifies the valence bands of defective GeO2 MLs through oxygen incorporation, while the conduction bands and electron effective mass recover to pristine-like characteristics. We further proved that the high O2 pressure hinders the formation of the O vacancy, while high temperature increases the oxidation rate in GeO2 ML. These atomic-level insights not only advance our understanding of oxidation resistance in 2D oxides but also provide guidelines for developing stable GeO2-based nanoelectronic devices.
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