Raman spectra of Ge_(x)As_(y)Se_(1-x-y) glasses

摘要

Various Ge-As-Se glasses spanning a mean coordination number (MCN) from 2.2 to 2.94 have been investigated using differential scanning calorimetry and Raman spectroscopy. The glass transition temperature T_(g) was found to increase with increasing MCN, except for those glasses located within the nanoscale phase-separated region of the phase diagram. The evolution of Raman features at wavenumbers from 150 to 350 cm~(-1) exhibits two transitionlike features. Merging of the 225 and 250 cm~(-1) modes at MCN(velence)2.5 is a symbol of the extinction of Se-Se bonds. Additionally, the appearance of two modes at 280-290 and 170 cm~(-1) at MCN > 2.7 come from the defect modes of ethanelike Ge_(2)Se_(6/2). The increase in the scattering from these defects is an important factor leading to enhanced optical loss in the glasses with high MCN.