Ion bombardment of Ni(110) studied with inverse photoemission spectroscopy and low-energy electron diffraction

摘要

Inverse photoemission spectroscopy (IPES) performed on clean Ni(110) reveals an unoccupied electronic surface state with energy similar to 2.5 eV above the Fermi level for emission near the (Y) over bar point of the Surface Brillouin Zone. Ion bombardment of the sample creates defects that reduce the intensity of the peak in IPES spectra. Sharp, intense diffraction spots in low-energy electron diffraction (LEED) patterns taken of the clean surface become dimmer after bombardment. Results of these measurements are compared to Monte Carlo simulations of the sputtering process to ascertain the approximate size of clean patches on the sample necessary to sustain the IPES and LEED features. At 170 K, the IPES surface state peak appears closely associated with the population of surface atomic sites contained in clean circular patches of about 50 atoms. The LEED patterns persist to greater degrees of sputtering and are associated with smaller clean patches. Both measurements performed at 300 K indicate significant self-annealing of the sputtering damage. (C) 2015 Elsevier B.V. All rights reserved.