Surface activated bonding of aluminum oxide films at room temperature

We have investigated the surface activated bonding (SAB) of deposited Al₂O₃ films by chemical vapor deposition under a short-time activated condition at room temperature. Although the surface energy for bonding of Al₂O₃ films was very low, that of Al₂O₃ film/sapphire bonding was approximately 1 J m ^{− 2} and more than 2 J m ^{− 2} for sapphire/sapphire bonding. Transmission electron microscopy showed an amorphous-like intermediate layer approximately 1 nm thick, observed at the bonding interface of Al₂O₃/Al₂O₃, but not in the bonding of Al₂O₃/sapphire, which suggests that the crystallinity of the Al₂O₃ film affects the bonding of Al₂O₃.