Hydrogen sensitivity of PdSiO2Si structure A correlation with the hydrogen-induced modifications on optical and transport properties of alfa-phase Pd films

The effects
studied through
of hydrogen absorption and desorption in Pd films are
reflectivity and conductance measurements. The data
show that there is an appreciable variation in both signals even when the
sample is exposed to a low hydrogen concentration that does not induce
the e/3 transition. The reflectivity variations are explained in terms of a
rise of the Fermi level in the bulk of the Pd film, while the conductance
decrease in a hydrogen atmosphere is related to the behaviour of scattering
centres of the absorbed hydrogen atoms. Such 'bulk' effects are correlated
to the flat-band voltage shift measured in Pd-gate MOS capacitors and two
contributions to this quantity are isolated by a temporal analysis of the
processes. A model based on two different sites for the absorbed hydrogen
atoms is proposed to explain the results.