High resolution electron energy loss spectroscopy: A new probe of subgap absorption in amorphous solids

Abstract

The use of high resolution electron energy spectroscopy (HREELS) as a new method for studies of subgap absorption in thin films of amorphous semiconductors is demonstrated. For a-Si films, the α(ω) values extracted from the measured loss spectra are in quantitative agreement with previous optical measurements. The method is also applied to both threefold and diamond-like amorphous carbon films, yielding α(ω) down to considerably lower energies (∼50 meV) than previously reported. The HREELS method is shown to be complementary to existing techniques in that it can access the regime of low energies and ultrathin films which is difficult to investigate with the conventional methods.