ZONE-AXIS BACKSCATTERED ELECTRON CONTRAST FOR FAST ELECTRONS

A dependent Bloch wave theory for inelastic scattering is adapted to p redict back-scattered electron (BSE) contrast from perfect crystals. T his is correlated with 300 keV data from a number of zone axes from sp inel, chromia, silicon, aluminium and gallium arsenide. This theory is shown to supersede an independent Bloch wave theory for BSE contrast which is incapable of accounting for asymmetry across polar axes. The orientation dependence of thermal dechannelling of fast electrons is s hown to be important. The BSE scattering potential is shown to approxi mate to a delta function scaled by the atomic number squared on each a tom.