Germanium K edge in GeO2 polymorphs. Correlation between local coordination and electronic structure of germanium

Abstract

The electronic properties of two room temperature persistent phases of germanium dioxide have been studied by means of experimental and theoretical techniques. We collected the Ge-K edge XANES spectra of these materials at the GILDA beamline of ESRF. The density of states of the two crystal phases, obtained from fully periodic Hartree-Fock and density functional calculations, is taken as the reference term to rationalise and assign the manifolds of the XANES spectra. Although this scheme requires a number of severe approximations, we obtained a good overall agreement between experiment and theory. The topological analysis of the theoretical electron density distribution in the crystals gave further information regarding the electronic properties of germanium dioxide. Experimental detailsCommercial q-GeO 2 (Aldrich, 99.998%) was used as such; r-GeO 2 was obtained by heating q-GeO 2 at 750 for 700 h.

Extreme biomimetic approach for developing novel chitin-GeO2 nanocomposites with photoluminescent properties

“…Note that the spectral pattern of the reference sample is consistent with that obtained for full-density hexagonal GeO 2 [48]. Regarding the rutile GeO 2 , it was previously shown that the structure of its unoccupied states differs from that of hexagonal GeO 2 [49]. Clearly, both spectra depicted in Fig.…”

Catalytic characterization of pure SnO2 and GeO2 in methanol steam reforming

“…In contrast, the tetragonal phase remains phase-pure after a similar treatment in hydrogen. This behaviour is not entirely clear, but seems to be a thermal annealing phenomenon, since it also happens -independently of the gas phase used -at 673 K. It also agrees well with studies of Bertini et al [20] who obtained a complete transformation into the tetragonal phase by simple annealing the hexagonal phase at 1023 K for 700 h. Possible consequences of this structural behaviour for the catalytic properties will be dealt with in the following section.…”

Local structure of epitaxial GeTe and Ge2Sb2Te5 films grown on InAs and Si substrates with (100) and (111) orientations: An x-ray absorption near-edge structure study

“…The energy separation between the two strong features of 6-7 eV indicates the formation of Ge-oxide. 31 Signals associated with the Ge-oxide were observed for all samples (GeTe and Ge 2 Sb 2 Te 5 ) grown on Si, the result demonstrating that use of Si substrates leads to enhanced oxidation. The observed oxidation process limited further studies of the uncapped films grown on Si substrates.…”