Interaction of hydrogen-terminated Si(100), (110), and (111) surfaces with hydrogen plasma investigated byin situreal-time infrared absorption spectroscopy

We have used infrared absorption spectroscopy (IRAS) in the multiple internal reflection (MIR) geometry to investigate the interaction of hydrogen-terminated Si(100), (110), and (111) surfaces with hydrogen plasma at room temperature. We have measured infrared absorption spectra in the Si–H stretching vibration region of the hydrogen-terminated surfaces during H-plasma treatment. IRAS data show that at initial stages of H-plasma treatment, surface hydride species (SiHx,x=1–3) are removed from the surface. A long-term H-plasma treatment of Si(100) and (110) surfaces reproduces monohydride species and creates hydrogen-terminated Si vacancies (VHx) at subsurface regions, i.e., near the surface. On Si(111), no hydride species are reproduced even after a long-term H-plasma treatment. We suggest that monohydride is rather stable against attack of hydrogen radicals as compared to higher hydride species, SiH2 and SiH3. We find that formation of VHx depends on the crystallographic orientation of the Si surface: VHx formation is more favored on Si(110) than on Si(100), and no VHx form on Si(111).