Dielectric and AC conductivity studies of CdSe nanocrystals doped sol-gel silica matrices

Silica glasses doped with varying concentrations of CdSe nanocrystallites are prepared by the sol-gel route. The dielectric response and the AC electrical conductivity of the samples are investigated for the frequency range 1 kHz-3 MHz at room temperature. The dielectric studies show low values for dielectric constant and loss at high frequencies. The conductivity values are found to be of the order of 10−5-10−7 S/cm for CdSe nanocrystallites and the conductivity curve reveals Jonscher's power-law dependence. The Cole-Cole parameters are calculated and the semicircles observed in the plots indicate a single relaxation process. This behaviour can be modeled by an equivalent parallel RC circuit. The complex impedance plots of CdSe doped silica glasses indicate the presence of ionic contribution to the electrical conductivity of these materials.