Measurements of insulator band parameters using combination of single-electron and two-electron spectroscopy

We describe the application of low energy time-of-flight coincidence (e,2e) spectroscopy for measurements of the energy band parameters of a dielectric. The (e,2e) spectrometer can operate also in a single-electron mode by switching off coincidence conditions, and can be used for recording electron energy loss spectra (EELS). Thus, the combination of (e,2e) and EELS allows the measurement of energy gap Eg, valence bandwidth ΔEval, electron affinity χ and excitonic levels position Eex of a dielectric. The energy band parameters of LiF film deposited on Si(001) surface are measured: Eg=(13.0±0.4) eV, ΔEval= (6.0±0.5) eV, Eex=(10.0±0.4) eV, χ=(1.0±0.4) eV.