Charge-sensitive secondary electron imaging of diamond microstructures

The surface orientation and detailed defect microstructure of polycrystalline diamond can be observed in a scanning electron microscope through local changes in the surface conductivity. The electron contrast in uncoated samples is straightforward to distinguish when the rms surface roughness is less than about 2 nm. This degree of smoothness occurs on some of the faceted surfaces of individual diamond grains but can also be achieved by polishing. The contrast, observable only in the secondary electron imaging mode, shows a strong dependence on both beam voltage and current. It is postulated that the contrast is produced solely by the differential rate at which the electron beam‐induced charge can be locally dissipated through crystalline defects and grain boundaries in the otherwise highly nonconductive diamond matrix. The appearance of the charge‐related contrast requires that highly connected pathways exist between the crystalline defects and the high‐angle grain boundaries.