Low-energy ion-beam induced effects in Al(1 0 0) surface studied using Rutherford backscattering and channeling

The results of low-energy ion spectroscopy can be compromised by the damage that the ions cause in surface layers of target single crystals, so it is important to characterize the impact of the probe ion on the target. In this investigation Al(1 0 0) single crystal surfaces have been irradiated at room temperature with 1 keV He+ and Ar+ ions typical of low-energy ion scattering spectroscopy (LEIS) and sample sputter cleaning, respectively, and the effects have been studied as a function of ion dose and annealing. Rutherford backscattering and channeling measurements were used to probe the depth distribution and annealing characteristics of the dechanneling yield induced by low-energy ion bombardment. Analysis of the Al surface peak area for channeled MeV He ions, as well as the dechanneling yield from well below the surface, indicated an unusual increase in the depth distribution of the backscattered ion yield from Al with increasing low-energy He+ ion dose. Thermal annealing of the crystal following irradiation with the highest He+ dose of 4×1017 ions/cm2 restored the dechanneled ion yield to its lower starting value, with the relatively low activation energy of 0.05 eV. The increase in backscattered ions is attributed to implanted He atoms located in the [1 0 0] channels. The Ar+ ion induced effects in the channeling spectrum are not as significant as those for He+ ions, even at the highest Ar+ dose of ∼1017 ions/cm2.