Electric Modulus and Impedance Spectroscopy Analysis on Selenium Nanoparticles at and Above Room Temperature

Here we report the electric modulus and impedance spectroscopy study on selenium nanoparticles in the temperature (T) range of 298K <= T <= 364K and in the frequency (f) of range 20Hz <= f <= 2MHz. Variation of the imaginary part of the electric modulus (M) with frequency yields well defined peaks (non-Debye type) which shift to higher frequency side with increasing temperature. From the response peaks of M versus f graphs relaxation times (t) are calculated which follows Arrhenius law with temperature with an activation energy of 0.27 eV. We observe that similar relaxation dynamics prevails at all temperatures with significant suppression of electrode effects. Role of grain and grain boundaries is also elucidated by the impedance spectroscopy analysis. We found that grain resistance varies from 0.07 M Omega to 0.48 M Omega whereas the grain boundary resistance varies in the range 0.09 M Omega to 0.82 M Omega. Both the grain and grain boundary resistances follow Arrhenius law with temperature having activation energies of 0.28 eV and 0.31 eV respectively. However both the grain and grain boundary capacitances exhibit weak temperature dependence.