Derivation of the near-surface dielectric function of amorphous silicon from photoelectron loss spectra

International audienceThe near-surface dielectric function ε(ℏω) of hydrogenated amorphous silicon (a-Si:H) films has been derived from X-ray photoelectron energy-loss spectra, over the energy range 0-45 eV. Removal of low lying single-electron excitations is a prerequisite step to proceed to the derivation of the single plasmon energy loss function Im[−1/ε(ℏω)] due to collective electron oscillations. Several methods are compared to separate interband transitions from bulk or surface plasmons excitation. The shape of interband excitation loss in the range 1-10 eV can be described by a Henke function; alternatively, its removal using a sigmoid weighting function is a low-noise and reliable method. After deconvolution of multiple plasmon losses and self-consistent elimination of surface plasmon excitation, the single plasmon loss distribution allows recovery of optical (ellipsometry) data measured in the near-UV to visible range