Total current spectroscopy

In total current spectroscopy (TCS) a beam of low energy (0–15 eV) electrons is directed upon a solid sample and secondary electron emission investigated by monitoring the current to the target, rather than by direct energy analysis of emitted electrons. A TCS signal is the derivative of the direct current with respect to the incident energy E1 displayed as a function of that energy, and obtained experimentally in ultra high vacuum conditions using simple modulation and lock in amplification techniques. A typical experimental arrangement is described and factors influencing a typical spectrum outlined. A simple background theory is discussed and it is shown how TCS is a powerful tool for studying not only the surface and near surface regions, but also bulk physics. In particular the technique has already found application in studies of work function, chemi- and physisorption, epitaxy, interband transitions, densities of states, excitons, impurity atom excitation, plasmons, radiation damage and the measurement of thicknesses of very thin surface layers.