Hydrogen effect on damage structure of Si(100) surface studied by in situ Raman spectroscopy

In situ Raman measurements have been performed on a Si(100) surface under irradiation by low-energy H+, D+ and He+. The intensity of the 520 cm-1 Raman peak of crystalline Si decreased almost linearly with the square root of displacement per atom (dpa), suggesting that the peak reduction originates from defect clusters but not single vacancies or interstitials. At a high dpa, the peak intensity became very low and broadened due to amorphization for all incident ions. In addition, the chemical effect of hydrogen was clearly observed, i.e., the reduction rate at low dpa was slightly enhanced by H+ and D+ irradiation as compared to that with He+, whereas H+ and D+ decelerated the amorphization as compared to He+. The initial damage enhancement is attributed to Si-H bond formation, whereas the later deceleration of the amorphization is attributed to the formation of H2 molecules recovering Si-Si bonds. (author)