STRUCTURE OF THE SI(100) SURFACE IN THE CLEAN (2X1), (2X1)-H MONOHYDRIDE, (1X1)-H DIHYDRIDE, AND C(4X4)-H PHASES

The structure of the Si{100} surface in the clean (2 X 1), (2 X 1)-H monohydride, (1 X 1)-H dihydride, and c(4 X 4)-H phases has been studied by time-of-flight scattering and recoiling spectrometry. The hydrogenated phases were formed by saturation exposure to atomic hydrogen at room temperature for (1 X 1), almost-equal-to 400-degrees-C for (2 X 1), and almost-equal-to 620-degrees-C for c(4 X 4). Time-of-flight spectra of scattered and recoiled neutrals plus ions were collected as a function of crystal azimuthal angle and primary-beam incident angle to the surface. Structural analyses of the phases were obtained from the azimuthal anisotropy of the recoiled silicon-atom flux from 4 keV Ar+ primary ions and from the critical incident angles for 4-keV Ne+ primary ions scattering along selected azimuths. Analysis of shadowing and blocking effects in these scattering and recoiling events, using calibrated shadow cones, is used in the structure determinations. The data provide a direct determination of the interatomic spacings in the outermost silicon layer of the four surface phases investigated.