Impact-collision ion-scattering spectroscopy of Cu(110) and Cu(110)-(2×1)-O using 5-keVLi+6

Abstract

Impact-collision ion-scattering spectroscopy was performed using 5-keV ${}_{}{}^6{}_{}{}^{}$ ${\mathrm{Li}}^{+}$ ions to study the Cu(110) and Cu(110)-(2×1)-O surfaces. Polar-angle scans were collected for scattering along the [11¯0], [11¯2], and [001] azimuths. These scans were quantitatively analyzed by comparing them to the results of an algorithm that combined a one-atom Monte Carlo computer simulation with various structural models to calculate trial polar scans. The results for the clean surface support a model in which the first- to second-atomic-layer spacing was contracted (10±5)% compared to the bulk spacings and the vibrational amplitudes of the atoms in the outermost atomic layer were enhanced by a factor of 1.5 over the bulk vibrational amplitude. For a surface with a 200 L oxygen exposure (1 L≡${10}^{\mathrm{-}6}$ torr sec), the results were not consistent with a buckled-row model, but indicated that every other [001] atom row was missing, the first-to second-layer spacing was expanded (25±10)%, and the second- to third-layer spacing was contracted (10±5)%. At higher oxygen exposures, the surface Cu layer became disordered.