Formation of a Modulated Void Structure in Heavy-Ion-Irradiated Amorphous Silicon

Abstract

a-Si:H was irradiated with 360 MeV Xe ions at 100 K in order to introduce defects in a controlled way. Subsequent investigations by small-angle X-ray scattering (SAXS) at room temperature lead to the following results and conclusions: i) Heavy-ion irradiation induces spherical voids of unknown hydrogen content with diameters growing from 30 Å after 1.0 · 1013 Xe ions/cm2 to 45 Å after 4.5 · 1013 Xe ions/cm2. ii) A well-defined interference maximum in the SAXS spectra develops upon irradiation indicating a modulated void structure, i.e. a typical distance between voids. iii) The total volume of the defect clusters as determined by SAXS agrees well with the amount of macroscopic swelling during irradiation. iv) The intensity increase towards very low q, which is usually observed for the SAXS of a-Si:H, is not affected by heavy-ion irradiation, suggesting that the SAXS signal from unirradiated specimens is not exclusively due to voids but also to other types of imperfections.