Derivation of dielectric function and inelastic mean free path from photoelectron energy-loss spectra of amorphous carbon surfaces

摘要: Abstract Photoelectron Energy Loss Spectroscopy (PEELS) is a highly valuable non destructive tool in applied surface science because it gives access to both chemical composition and electronic properties of surfaces, including the near-surface dielectric function. An algorithm proposed for real materials make full use experimental X-ray photoelectron spectra (XPS). To illustrate capabilities limitations this algorithm, function e( ℏ ω) wide range amorphous carbon (a-C) thin films derived from energy losses measured XPS, using response theory which relates bulk plasmon (BP) loss distribution. Self-consistent separation vs excitations, deconvolution multiple BP evaluation Bethe-Born sensitivity factors distributions are crucial obtain several material parameters: (1) excitation, (2) (3–5 nm depth sensitivity), (3) inelastic mean free path, λP (E0), (4) excitation parameter, (5) effective number NEFF valence electrons participating plasma oscillation. This analysis has been a-C a-C:H grown by physical methods with (sp3/sp2 + sp3) hybridization, optical gap average values. Different assessed accurately remove photoemission peak tail at low (0–10 eV) due many-body interactions during photo-ionization process. The σ + π represents main energy-loss channel a-C; as C atom density decreases, (970 eV) increases 1.22 nm 1.6 nm, assuming cutoff wavenumber given electron model. π-π* σ-σ* transitions observed retrieved discussed (sp3/sp2 + sp3) C hybridization compared literature results.