Study of oxygen adsorption on β-Si3N4(0 0 0 1) by the density functional theory

The density functional theory (DFT) B3LYP method is used to theoretically investigate the interaction of O2 with the β-Si3N4 surface (0 0 0 1) at 1200 °C. All the calculations have been performed at the 6-31G∗ basis set level using H-saturated cluster. From the total energy minimization, the chemisorption on the center of the molecule lying above an Si site and the molecular axis paralleling to the surface is the most stable. After adsorption, the O-O bond is easier to dissociate compared to the free O2. The electron transferred from the substrate to the O2 molecule occupies the O2 anti-bonding orbital, thus leading to a weakening off the bond strength, which is reflected by the elongated O2 bond length. The changing trend of the O-O population and vibrational frequency is consistent with the change of the O-O bond length. The significant chemisorption energy and the short adsorption bond length indicate that the oxidation occurs on the β-Si3N4(0 0 0 1) surface at 1200 °C more easily.