Direct view on the structure of different glass fracture surfaces by atomic force microscopy

Silica, silicate, borosilicate and heavy metal fluoride glasses were fractured under UHV conditions. The fracture mirror, surfaces were imaged then by atomic force microscopy. The atomically resolved images display a fully interconnected random network structure for the silica glass, modified random network structures with percolation paths for the silicate glasses, a structure with higher connectivity with some short percolation paths only for the borosilicate glass and a strongly interconnected structure for the heavy metal fluoride glass with some chain- and ring-like structure elements. Sodium diffusion, which is supposed to follow mainly these percolation paths, is qualitatively in line with the number, length and width of these paths.