Published by the American Physical Society through the American Institute of Physics
Physical Review B, Condensed Matter and Materials Physics vol:65 issue:24
The optical properties of sodium-deficient alpha(')-NaxV2O5 (0.85less than or equal toxless than or equal to1.00) single crystals are analyzed in the wide energy range, from 0.012 to 4.5 eV, using ellipsometry, infrared reflectivity, and Raman-scattering techniques. The material remains insulating up to the maximal achieved hole concentration of about 15%. In sodium-deficient samples the optical absorption peak associated to the fundamental electronic gap develops at similar to0.44 eV. It corresponds to the transition between vanadium d(xy) and the impurity band, which forms in the middle of the pure alpha(')-NaV2O5 gap. Raman spectra measured with incident photon energy larger than 2 eV show strong resonant behavior, due to the presence of the hole-doping activated optical transitions, peaked at similar to2.8 eV.