RDF analysis of ion-amorphized SiO_2 and SiC from electron diffraction using post-specimen scanning in the field-emission scanning transmission electron microscope

摘要

Radial density functions (RDFs) provide important information about short- and intermediate-range structure of topologically-disordered materials such as glasses and irradiation-amorphized materials. We have determined RDFs for irradiation-amorphized SiO_2, AlPO_4 and SiC by energy-filtered electron diffraction methods in a field-emission scanning transmission electron microscope (FEG-STEM) equipped with a digital parallel-detection electron energy-loss spectrometer. Post-specimen rocking was used to minimize the effects of spherical aberration in the objective lens, which interfere with the acquisition of data collected by pre-specimen rocking. Useful energy-filtered data has been collected beyond an angular range defined by q=2 sin( THETA /2)/ lambda =25 nm~(-1).