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Title: Determining the band gap and mean kinetic energy of atoms from reflection electron energy loss spectra

Reflection electron energy loss spectra from some insulating materials (CaCO{sub 3}, Li{sub 2}CO{sub 3}, and SiO{sub 2}) taken at relatively high incoming electron energies (5–40 keV) are analyzed. Here, one is bulk sensitive and a well-defined onset of inelastic excitations is observed from which one can infer the value of the band gap. An estimate of the band gap was obtained by fitting the spectra with a procedure that includes the recoil shift and recoil broadening affecting these measurements. The width of the elastic peak is directly connected to the mean kinetic energy of the atom in the material (Doppler broadening). The experimentally obtained mean kinetic energies of the O, C, Li, Ca, and Si atoms are compared with the calculated ones, and good agreement is found, especially if the effect of multiple scattering is taken into account. It is demonstrated experimentally that the onset of the inelastic excitation is also affected by Doppler broadening. Aided by this understanding, we can obtain a good fit of the elastic peak and the onset of inelastic excitations. For SiO{sub 2}, good agreement is obtained with the well-established value of the band gap (8.9 eV) only if it is assumed that the intensitymore » near the edge scales as (E − E{sub gap}){sup 1.5}. For CaCO{sub 3}, the band gap obtained here (7 eV) is about 1 eV larger than the previous experimental value, whereas the value for Li{sub 2}CO{sub 3} (7.5 eV) is the first experimental estimate.« less
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [4]
  1. Atomic and Molecular Physics Laboratories, Research School of Physics and Engineering, Australian National University, Canberra ACT (Australia)
  2. (Brazil)
  3. Nuclear Research Center — Negev, Beer-Sheva 84190 (Israel)
  4. Physics Department, Ben-Gurion University of the Negev, Beer-Sheva 84105 (Israel)
Publication Date:
OSTI Identifier:
22489564
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 143; Journal Issue: 10; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CALCIUM CARBONATES; COMPARATIVE EVALUATIONS; DOPPLER BROADENING; ELECTRONS; ENERGY-LOSS SPECTROSCOPY; EV RANGE; EXCITATION; KINETIC ENERGY; LITHIUM CARBONATES; MULTIPLE SCATTERING; PEAKS; SILICA; SILICON OXIDES; SPECTRA