Ion bombardment induced surface structures on Cu(001) have been studied under conditions obeying the previously “coined athermal Bradley-Harper (BH) region.” Off-normal ion impact along the ⟨110⟩ and the ⟨100⟩ azimuth at 200 K gives rise to different high-resolution low-energy electron-diffraction patterns. Unanticipated and marked deviations from the inherent fourfold symmetry are obtained already at a polar angle of incidence as low as 10°. Experiments with 800 eV Ar+ ions (flux 6×10 12 ions cm−2 s−1 and fluence 4.3×10 16 ions cm−2) clearly show BH behavior for bombardment along  in contract to bombardment along . This observation is attributed to the higher probability for surface penetration of ions when incident along ⟨100⟩ . This remarkable finding is further corroborated by measurement at various energies between 0.2 and 2 keV along .
|Journal||Physical review B: Condensed matter and materials physics|
|Publication status||Published - 2010|