Optical Spectroscopy of PdO and Pd thin Films under hydrogen exposure

Palladium oxide (PdO) is a p-type semiconductor with a bandgap appropriate to absorb light in the visible range an thus generating an electrical current. This bandgap, being of the order of 2.5 eV, remains yet not accurately determined. We are currently setting up a new experiment in which we are able to monitor the evolution of reflectivity or transmission, for several wavelengths in the visible spectrum, and the resistivity as a function of the exposure time to hydrogen. We should be able to calculate the evolution of bandgap of the semiconductor as a function of reduction from the reflectivity data. Pd films also change reflectivity properties during hydrogen absorption. The experimental set up consist of a tungsten light, Spectrapro 275 monochromator with a diffraction grid of 1200 lines/mm, and a silicon diode detector. Preleminary results will be shown. Based on these data we expect to depict a model for the changes measured.