Hydrogen induced Si surface segregation on Ge-covered Si(001)

Using Fourier transform infrared-attenuated total reflectance spectroscopy in conjunction with hydrogen adsorption to probe surface layer composition, we observe a reversible place exchange between Ge and Si on Ge-covered Si(001) when the surface is dosed with atomic H at elevated temperatures. First-principles calculations confirm a thermodynamic driving force for this place exchange. To explain the intriguing kinetics of the place exchange, which shows no time dependence, we propose a dimer-vacancy diffusion-assisted mechanism limited by vacancy interactions.