Measurement of the spectral momentum distribution of valence electrons in amorphous carbon by (e,2e) spectroscopy

Abstract

The spectral momentum density of the valence band of arc evaporated amorphous carbon has been measured by (e, 2e) spectroscopy with significantly improved energy resolution relative to earlier studies. The valence band has been studied over a range of momenta from 0 to 1.6 a.u. with a resolution of 0.15 a.u. and over a range of binding energies from 9 eV above to 35 eV below the Fermi energy with a resolution of 1.5 eV. As seen in earlier studies, two major peaks are observed in the spectral momentum density which previously have been associated with cr and vr bands in graphite. A third feature in the spectra, a weak shoulder approximately 4 eV below the Fermi energy, is observed. A heuristic model is introduced based on the assumption that the spectral momentum density of evaporated amorphous carbon is an angular average of the spectral momentum density of graphite. The behavior of the strongest feature in the experimental spectra is described well by this model, but the other two features, which are in the energy range of the graphitic x, o2, and cr3 bands, are poorly represented by the model. It is suggested that the poor agreement is due to rehybridization of these graphitic bands.

Latest developments in (e,2e) on solids

“…His result is shown in fig.6(b) together with some data obtained using a symmetric coplanar spatrometer [13,7]. The agreement between the calculated innervalence a band and the observed band E = 20eV at q = 0 is excellent.…”

“…Kheifets [13] has carried out a linear muffin-tin orbital calculation for the electronic structure of graphite, and then spherically averaged in momentum space the resulting dispersion curves and momentum densities. His result is shown in fig.6(b) together with some data obtained using a symmetric coplanar spatrometer [13,7].…”

Electronic-structure investigation of oxidized aluminum films with electron-momentum spectroscopy

“…1 This was demonstrated by a series of (e,2e) experiments on solid targets [2][3][4][5][6][7][8][9][10] in the last few years. In these experiments, the (e,2e) spectrometer 11 of The Flinders University of South Australia was used.…”

“…12͔͒ and significantly improved both energy and momentum resolution. In addition to the energy-resolved momentum distribution of electrons in valence bands 5,[8][9][10] and core levels, 4,9 which can be uniquely measured by EMS, information has also been obtained on the influence of lattice order on the electronic structure, 6 the electronic structure of adsorbates, 7,9 and the annealing effects on the electronic structure of the surface. 3 The targets used in these investigations include carbon ͑amorphous carbon, graphite, highly oriented pyrolitic graphite, and diamondlike amorphous carbon͒, semiconductors ͑amorphous silicon and amorphous germanium͒, and a semiconductor compound ͑polycrystalline silicon carbide͒.…”

Electronic band structure of calcium oxide

“…A faint parabolic feature, having its minimum superimposed onto the s-band and spreading nearly to the p-band belongs to the σ-valence band of am-C [50]. A much weaker intensity from the π-bands of am-C is superimposed onto the p-band.…”