First-principles calculations were made of metal/HfO2 interfaces in the presence of O vacancies, where Pt, Al, Ti and Ag were considered as electrodes. It was found that O vacancies were strongly attracted to the interface with binding energies of up to several eV. In addition, the vacancy affinity of interfaces was proportional to the work function of metals, which was understood by the transition level of the vacancy and metal-Hf bonding. Interfacial segregation of vacancies significantly affects effective work functions of p metals. The results were consistent with flat-band shifts in p-type field effect transistors employing high-k dielectrics and metal gates.

Segregation of Oxygen Vacancy At Metal-HfO2 Interfaces. E.Cho, B.Lee, C.K.Lee, S.Han, S.H.Jeon, B.H.Park, Y.S.Kim: Applied Physics Letters, 2008, 92[23], 233118