Charge Contrast Imaging of Nonconductive Samples in the High-Vacuum Field Emission Scanning Electron Microscope

The charge contrast images (CCI) on insulating or poorly conducting samples were observed under steady-state charging conditions with a thermal field emission scanning electron microscope under high vacuum by using, an Everhart-Thornley detector. The charge contrast on plumbous titanate-nickel composite particles and patterned sapphires could be the indicators of near-surface features, compositional variations and conductivity distributions. Optimum imaging conditions for observing the CCI include the electron energy, the electron flux density and the electron dose. Contrast characteristics associated with surface and near-surface secondary electron emission yield enhanced above the trapped charge-up regions, as charge trapping selectively enhanced the poorly conductive phase and lattice distorted area.