A First-Principles Study on the Oxygen Adsorption and Interface Characteristics with a-GeO2 of Ge[001] Nanowire

First-principles calculations were performed to study the atomic and the electronic structures of the oxygen adsorption on the sidewalls of Ge[001] nanowires. For several possible adsorption sites, the adsorption energy of atomic oxygen, as well as the atomic configuration and electronic properties of the adsorbed structure, were examined. The adsorption stability is not much affected by the nanowire diameter for diameters ranging from 0.8 nm to 2 nm while the electronic structures like band gap and gap states, vary with the nanowire diameter. The interface between the Ge nanowire and amorphous GeO2 (a-GeO2) was also investigated. The interface region is composed of Ge suboxides like those between Ge bulk slab and a-GeO2. The valence band offsets between Ge nanowire and a-GeO2 decreases considerably as the diameter of nanowire shrinks while the conduction band offsets show less dependence on the diameter of the nanowire.