Surface Structure from Angle-Resolved Secondary-Ion Mass Spectrometry: Oxygen on Cu(001)

Abstract

Measured angular distributions for ${\mathrm{O}}^{\ensuremath{-}}$ and ${\mathrm{Cu}}^{+}$ ejected by 1500-eV ${\mathrm{Ar}}^{+}$-ion bombardment of chemisorbed oxygen on Cu(001) exhibit anisotropies which vary by greater than a factor of 2. Molecular-dynamics calculations of the ion-impact event agree well with experiment if the oxygen atom is placed in a fourfold coordination site 1.2-1.5 \AA{} above the Cu(001) plane. Angle-resolved secondary-ion mass spectrometry is proposed as a powerful new method for the determination of adsorbate positions.