AC transport properties of nanocrystalline SnO2 semiconductor

The complex dielectric constant ɛ* has been found to vary with frequency which is attributed to the multi-relaxation time constants of the energy states responsible for conduction mechanism. At any particular frequency, ɛ* has been found to increase with temperature. The frequency dependence of loss tangent tan δ has been explained with the help of the equivalent circuit model. The observed frequency dependence of ac conductivity has been found to obey the power law: σac ∝ ωS, where variation of S with temperature indicates multi-hopping conduction mechanism in nanocrystalline SnO2 samples. The complex impedance plots of Z′ versus Z″ at different temperatures have been found to be single semicircular arcs with a non-zero intersection with the real axis in the high frequency region and have their centres lying below the real axis at a particular angle of depression, indicating multirelaxation processes in the material.