A simple method for surface and ultrathin film characterization

The method depends on monitoring variations of secondary electron emission as a function of changes in surface structure and composition. By measuring the crystal current i_cc and its variation with incident beam energy, E, surface changes can be measured rapidly and precisely. The principle of the method is already used qualitatively in secondary electron emission microscopy. If E is adjusted to give zero crystal current (E_zcc), and changes are followed from either variations in i_cc or E_zcc, then the measurements obtained during adorption are comparable to (but can be more precise than) those obtained from Auger spectroscopy. Results are presented for copper surfaces during cleaning cycles and during the adsorption of lead overlayers. Various applications can be envisaged, especially for rapid changes during segregation, diffusion or desorption.