Interaction of the O atom with the InSe monolayer: A first-principles study

The interaction of the O impurity atom with the InSe monolayer has been investigated by using first-principles calculations. O atoms energetically highly tend to be located at the inner of the material between the In-In bond. The energy barrier (0.53 eV) for the O diffusion from the topmost atomic layer to the material inner is much smaller than that (1.12 eV) for the diffusion across the topmost atomic layer. These suggest that the O atom on the topmost atomic layer can rapidly diffuse into the material inner far below room temperature. However, the rapid diffusion of the O atom in the material inner may need an elevated temperature, due to its higher diffusion energy barrier of 0.99 eV. For the electronic structure, O impurity single atoms are most likely to only induce a slight change in the bandgap, and moderate changes in the band dispersion and the carrier effective masses of the valence and conduction bands. Further, a higher concentration of O impurities in the inner of InSe has been studied. Our studies are helpful for understanding of the oxidation, enviromental stability, and electronic properties of InSe two-dimensional semiconductors at the atomic level, due to the O impurity.