DARK-FIELD CONTRAST OF ELEMENTS IN HIGH-VOLTAGE ELECTRON-MICROSCOPY

A new and simple expression developed by us has been used for the esti mation of contrast of thin amorphous specimens in the tilted-beam mode of dark field (DE) imaging using a conventional transmission electron microscope (CTEM). DF contrasts calculated for thin amorphous films o f some representative elements in the electron accelerating voltage ra nge between 0.1 to 3.0 MV have been compared with the corresponding br ight field (BF.) contrasts. The magnitude of the gain in contrast in t he DF mode compared with BF one, observed over a wide range of acceler ating voltage (phi), microscope aperture (alpha) and atomic number (Z) of elements, has been highlighted.