Grazing-incidence transmission SAXS investigation of conical etched ion tracks in SiO2

Abstract

We present results of a systematic study of the morphology of etched ion tracks in amorphous SiO2 using a combination of small angle X-ray scattering (SAXS) and scanning electron microscopy. We focus on the analysis of SAXS data obtained in grazing incidence (GISAXS) configuration from conical etched channels with a base radius of less than 50 nm. Swift heavy ion irradiation of 2 μm thick thermally grown SiO2 layers with 185 MeV Au ions was conducted at the ANU Heavy Ion Accelerator Facility in Canberra, Australia. Low irradiation fluences of 109 ions per cm2 were chosen to minimize overlap of the etched structures. Irradiated samples were etched in aqueous hydrofluoric acid (HF) with concentrations of 5%, for etching times between 30 and 90 s. In grazing incidence configuration, we obtain good data quality from the very small cones, since the X-ray beam interacts with a greater proportion of the sample at the very low incidence angle compared with normal transmission mode.