Local structure of porous InSb films: From first to third-shell EXAFS investigation

Extended x-ray absorption fine structure spectroscopy was used to investigate the neighborhood of In and Sb atoms in InSb films deposited by magnetron sputtering and subsequently irradiated with 14 MeV Au+6 ions at room temperature, with ion fluences ranging from 1 × 1013 cm−2 to 2 × 1014 cm−2. For the first nearest-neighbor shell, the structural parameters were unaffected by ion irradiation up to 1 × 1014 cm−2. However, the irradiation-induced disorder was observed for the second and third nearest-neighbor shells through decrease (increase) of the coordination number (Debye-Waller factor). Upon ion irradiation, InSb films become porous while still retaining part of their crystallinity. Using x-ray absorption near edge structure, it was observed that In K-edge and Sb K-edge positions are unchanged as a function of ion fluence in InSb, evidencing that the energy of the element-specific unoccupied local states is independent of ion fluences used in this work. For the highest irradiation fluence (2 × 1014 cm−2), part of InSb is converted to In2O3, Sb2O3, Sb2O5 and metallic Sb, representing a fraction of ~26%, ~7%, ~11%, and ~9%, respectively. This increase in antimony and indium oxides at this irradiation fluence was attributed to the combination of the high reactivity, in the presence of oxygen, of the InSb surface with the enhanced surface-area-to-volume ratio of the porous structure.