Raman spectra of P-, Sb-, or Bi-dopedGexSe1−xbulk glasses

Raman spectra for the P-, Sb-, or Bi-doped ${\mathrm{Ge}}_{0.2}$ ${\mathrm{Se}}_{0.8}$ glass system were obtained at room temperature. Variations of the intensity of three main peaks, A (197 ${\mathrm{cm}}^{\mathrm{-}1}$), B (215 ${\mathrm{cm}}^{\mathrm{-}1}$) and C (254 ${\mathrm{cm}}^{\mathrm{-}1}$) are measured as a function of the doping concentration. The A and B peaks are assigned to the ${\mathit{A}}_1$ modes in the corner and edge-sharing Ge(${\mathrm{Se}}_{1/2}$ ${)}_4$ tetrahedral units, respectively. The C peak is due to the vibration of the Se-Se bonds in the Se-rich region. The intensity ratios I(B)/I(A) are interpreted by an extended stochastic random-network model. The probability of the existence of edge-sharing units relative to corner-sharing units is determined. The intensity ratio I(C)/[I(A)+I(B)] is explained by assuming that chemically ordered bonds are formed. The coordination numbers of Ge, Se, and the dopant atoms are 4, 2, and 3, respectively, and the Ge-Se bond is considered to be most stable.