Analysis of the reconstructed Ir(110) surface from time-of-flight scattering and recoiling spectrometry

Abstract

Time-of-flight scattering and recoiling spectrometry and low-energy electron diffraction are used to analyze the reconstructed Ir(110) surface. The structure is determined from scans of (i) backscattering (BS) versus incident angle \ensuremath{\alpha}, (ii) forward scattering (FS) versus \ensuremath{\alpha}, and (iii) FS versus scattering angle \ensuremath{\theta} along different azimuths \ensuremath{\delta} with use of a pulsed 4-keV ${\mathrm{Ar}}^{+}$-primary-ion beam. Plots of BS intensities in (\ensuremath{\alpha},\ensuremath{\delta}) space provide scattering structural contour maps that expose the surface symmetry. Measurements of BS intensities as a function of \ensuremath{\alpha} along the [11\ifmmode\bar\else\textasciimacron\fi{}0] azimuth, where the interatomic spacings are not affected by reconstruction, are used to obtain experimental points on the shadow cones. These points are used to calibrate the screening constant of the interatomic potential used in the trajectory simulations. The experimental data and calibrated simulations are applied to an analysis of the surface reconstruction. The results are consistent with a model in which the reconstructed surface consists of primary domains of faceted (1\ifmmode\times\else\texttimes\fi{}3) structures (with two missing first-layer rows and one missing second-layer row) along with secondary domains of (1\ifmmode\times\else\texttimes\fi{}1) structures (with no missing rows). Estimates of the interatomic spacings in the (1\ifmmode\times\else\texttimes\fi{}3) domains indicate that the second-layer atoms are shifted from the bulk values laterally by \ensuremath{\sim}6% towards the center of the trough and that the first- to second-layer spacing is contracted by \ensuremath{\sim}8%.