The effect of Co-60 (gamma-ray) irradiation on the electrical and dielectric properties of Au/Polyvinyl Alcohol (Ni,Zn-doped)/n-Si Schottky barrier diodes (SBDs) has been investigated by using capacitance-voltage (C-V) and conductance-voltage (G/omega-V) measurements at room temperature and 1 MHz. The real capacitance and conductance values were obtained by eliminating series resistance (R-s) effect in the measured capacitance (C-m) and conductance (G(m)) values through correction. The experimental values of the dielectric constant (epsilon'), dielectric loss (epsilon ''), loss tangent (tan delta), ac electrical conductivity (sigma(ac)) and the real (M') and imaginary (M '') parts of the electrical modulus were found to be strong functions of radiation and applied bias voltage, especially in the depletion and accumulation regions. In addition, the density distribution of interface states (N-ss) profile was obtained using the high-low frequency capacitance (C-HF-C-LF) method for before and after irradiation. The N-ss-V plots give two distinct peaks for both cases, namely before radiation and after radiation, and those peaks correspond to two different localized interface states regions at M/S interface. The changes in the dielectric properties in the depletion and accumulation regions stem especially from the restructuring and reordering of the charges at interface states and surface polarization whereas those in the accumulation region are caused by series resistance effect. (C) 2011 Elsevier Ltd. All rights reserved.