Anomalous anisotropy in athermal Bradley-Harper roughening of Cu(001)

Abstract

Ion bombardment induced surface structures on Cu͑001͒ have been studied under conditions obeying the previously "coined athermal Bradley-Harper ͑BH͒ region." Off-normal ion impact along the ͗110͘ and the ͗100͘ 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 ϫ 10 12 ions cm −2 s −1 and fluence 4.3 ϫ 10 16 ions cm −2 ͒ clearly show BH behavior for bombardment along ͓100͔ in contract to bombardment along ͓110͔. This observation is attributed to the higher probability for surface penetration of ions when incident along ͗100͘. This remarkable finding is further corroborated by measurement at various energies between 0.2 and 2 keV along ͓100͔.

Optical characterization of the evolution of ion-induced anisotropic nanopatterns on Ag(001)

“…26,[31][32][33] Second, the result of the ion impact shows a strong dependence on the crystal structure observed at angles of incidence near the critical angle for channeling. 34…”

Characterization of nanometre-scale patterns on Cu(001) and Ag(001) by means of optical spectroscopy and high-resolution electron diffraction

“…Secondly, the result of the ion impact shows a strong dependence on the crystal structure observed at angles of incidence near the critical angle for channeling [65].…”

Material characterization and modification using helium lon microscopy : various examples

“…The pattern orientation along a specific crystallographic direction can be explained by considering its formation as a result of the suppression of interlayer diffusion by the step edge or Ehrlich-Schwoebel barrier [77,79,[83][84][85][86][87]. The activation energy for vacancy diffusion on Au{111} is much higher than the one for adatoms [88], hence we can suppose that at room temperature adatoms are dominantly responsible for the pattern formation.…”