Imaging of surface strain and polishing artefacts in fused silica by environmental scanning electron microscopy

The recently developed application of charge contrast imaging (CCI), available in variable pressure or environmental scanning electron microscopes (ESEM), has been found to provide images of near surface strain around micro-indentations in fused silica glass. Results suggest this strain contrast information is derived from within a few nanometres of the material surface, making CCI an invaluable tool for the study of nanometre scale surface deformation. Images of indentation strain have also been imaged using backscattered electron (BSE) imaging. The CCI technique has also been applied to the study of fused silica surfaces polished by chemically active polishing abrasives. In the samples studied, CCI provides unique images of linear defects residing below layers of chemically adhered polishing compound. Visualisation of surface strain on sub-nm rms glasses provides supporting evidence for plastic (permanent) deformation of the glass surface at the nanometre level during polishing with certain abrasives and for chemical interactions between the polishing abrasive and glass surface.