The relation between contact potential and planar conduction as a-Si : H films undergo gas adsorption or temperature changes

When the free surface of an amorphous silicon thin film is exposed to water vapour, the contact potential and planar conductance simultaneously change. For three samples, we correlate the two measurements and interpret them in terms of adsorbate induced changes of the surface potential, similar to field effect experimental analysis. During temperature cycles, there is a strong correlation between non-linear portions of the log conductance versus 1/T plots and the variation of the contact potential.