Angle-resolved x-ray photoelectron spectroscopy study of GeOx growth by plasma post-oxidation**Project supported by the National Natural Science Foundation of China (Grant Nos. 61574168 and 61504163).

Abstract

The growth process of GeOx films formed by plasma post-oxidation (PPO) at room temperature (RT) is investigated using angle-resolved x-ray photoelectron spectroscopy (AR-XPS). The experimental results show that the distributions of the Ge4+ states, a mixture of the Ge2+ and Ge3+ states, and the Ge+1 states are localized from the GeOx surface to the GeOx/Ge interface. Moreover, the Ge+1 states are predominant when the two outermost layers of Ge atoms are oxidized. These findings are helpful for establishing in-depth knowledge of the growth mechanism of the GeOx layer and valuable for the optimization of Ge-based gate stacks for future complementary metal–oxide–semiconductor (MOS) field-effect transistor (CMOSFET) devices.