Electron image contrast from carbonaceous material: a comparison of theory with experiment

The authors have proposed and tested a means of predicting the electron-optical image contrast of carbonaceous specimens consisting of more than one atomic species, the ultimate purpose of which is the prediction of image contrast for unstained biological objects. Since the existing scattering theories are strictly applicable only to specimens of a single atomic species, they first measured the image contrast of carbon films of known thickness to verify the scattering theory. They then determined the image contrast of polystyrene latex (PSL) spheres of measured diameter. All measurements were performed at 100 keV. The theoretical image contrast for the carbon films agrees with the measurements to within +or-20%.