Study of the occupied electronic density of states of carbon samples by using second derivative carbon KVV Auger spectra

The Effect of Stress in the Density of States of Amorphous Carbon Films Determined by X-Ray Excited Auger Electron Spectroscopy

“…However, the energy shift observed in the Auger electrons in Figure 2(a) hides details that are revealed by the second derivative method, as shown in Figure 3, adopting the method described in [6] but using the Savitzky-Golay smoothing procedure. These details reveal electronic transitions with more defined energy as seen by the presence of additional peaks in samples with higher bombardment energies, indicating atomic relaxation channels and uniformity of the C atoms in the matrix.…”

“…For example, the line shape of the second derivative of the KVV spectrum of diamond is characteristic of the pure sp 3 -hybridized states tetrahedrally bonded ( -bonds) as well as that of graphite with line shape due to sp 2 hybridization ( -bonds in plane and -bonds normal to the -bond, for a threefold coordination). As for a-C the line shape has contribution of both sp 3 and sp 2 hybridization [6], and evidently the density of states (DOS) of a-C is composed of -and * -bonds and - * -bonds. However, the spectroscopy techniques normally investigate occupied states ( and orbitals) of DOS in the valence band.…”

“…The method of the second derivative presented by Lascovich and Santoni [6] has the advantage of showing in more detail the fine structures of the peaks corresponding to the original full spectrum; that is, to a first approximation, the minimum found in the second derivative of an Auger spectrum should correspond to a maximum of one full original peak. Making use of a simplified model (where the interactions between the final stage of holes are negligible), they showed that the KVV spectra reflect well the behavior of the DOS in comparison with theoretical data.…”

“…With regard to the first method, it has been largely used to determine the energy and linewidth of specific orbitals, which are used to characterize the material. For instance, it has been shown that graphitic samples exhibit a width of ∼23 eV [4,6].…”

“…Auger electron spectroscopy (AES) has been widely used in the investigation of carbon bonds in carbon based materials thin films because the main peak of the carbon Auger transition involves valence states [4][5][6][7][8][9][10][11][12][13]. The line shape of the Auger spectrum is assumed to be a self-convolution of the DOS [10]; that is, the Auger electrons exhibit energy proportional to the occupied state band energy.…”