Raman Study of the Semiconductor-Metal Transition inTi2O3

The Raman spectrum of ${\mathrm{Ti}}_2$ ${\mathrm{O}}_3$ exhibits seven modes as predicted for the corundum structure. The persistence of all seven of these modes above the semiconductor-metal transition temperature indicates no space-group change on going through the phase transition. The $A_{1g}$ mode at 269 ${\mathrm{cm}}^{-1\mathrm{}}$ (300 °K) exhibits a significant frequency change (about 16%) and a large intensity increase relative to the other modes in the temperature range of the semiconductor-metal transition. These results are interpreted in terms of electronic and structural changes during the phase transition.