Direct observation of fine structure in ion tracks in amorphous Si 3N 4 by TEM

Abstract

Thin films of amorphous Si 3N 4 (thickness 20 nm) were irradiated with 120-720 keV C 60+,2+ ions and observed using transmission electron microscopy (TEM). The ion track produced in an amorphous material was directly observed by TEM. For quantitative analysis, the ion tracks were also observed using high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). The observed ion track consists of a low density core (radius ∼2.5 nm) and a high density shell (width ∼2.5 nm), which is very similar to the ion tracks in amorphous SiO 2 irradiated with high energy heavy ions observed by small angle X-ray scattering (SAXS). Although the observed ion tracks may be affected by surface effects, the present result indicates that TEM and HAADF-STEM have potential to observe directly the fine structures of ion tracks in amorphous materials. © 2012 Elsevier B.V. All rights reserved.