HYDROGEN-INDUCED SI SURFACE SEGREGATION ON GE-COVERED SI(001)

Using Fourier transform infrared-attenuated total reflectance spectros copy in conjunction with hydrogen adsorption to probe surface layer co mposition, we observe a reversible place exchange between Ge and Si on Ge-covered Si(001) when the surface is dosed with atomic H at elevate d temperatures. First-principles calculations confirm a thermodynamic driving force for this place exchange. To explain the intriguing kinet ics of the place exchange, which shows no time dependence, we propose a dimer-vacancy diffusion-assisted mechanism limited by vacancy intera ctions. [S0031-9007(98)07429-8].