CHARGE-SENSITIVE SECONDARY-ELECTRON IMAGING OF DIAMOND MICROSTRUCTURES

The surface orientation and detailed defect microstructure of polycrys talline diamond can be observed in a scanning electron microscope thro ugh local changes in the surface conductivity. The electron contrast i n uncoated samples is straightforward to distinguish when the rms surf ace roughness is less than about 2 nm. This degree of smoothness occur s on some of the faceted surfaces of individual diamond grains but can also be achieved by polishing. The contrast, observable only in the s econdary electron imaging mode, shows a strong dependence on both beam voltage and current. It is postulated that the contrast is produced s olely by the differential rate at which the electron beam-induced char ge can be locally dissipated through crystalline defects and grain bou ndaries in the otherwise highly nonconductive diamond matrix. The appe arance of the charge-related contrast requires that highly connected p athways exist between the crystalline defects and the high-angle grain boundaries.