Gas indiffusion contribution to impedance in tin oxide thick films

The ac electrical resistance and capacitance of SnO2 thick films under vacuum and air atmosphere were analyzed using the Cole–Cole plot. To fit the experimental results, a simple circuit model that considers a capacitance and a resistance in parallel was employed. An explanation for the resistance variation considering spherical grains with different characteristics is proposed. A careful analysis of the resulting depletion layers and doping levels gives evidence for gas diffusion into the grains.