HYDROGEN-INDUCED RELAXATIONS IN DISORDERED DIELECTRICS

In many non-crystalline Or amorphous dielectrics, for example in alumi numoxide, siliconnitride, siliconoxide, or polyimide, the Kohlrausch b ehaviour of the time dependent polarization current j similar to(-alph a) is observed. This empirical law can be detected from the sub-micros econd range up to several thousand seconds indicating a broad distribu tion of relaxation times. The effect is caused by protons fluctuating in double well potentials between neighboured electronegative atoms, i . e. oxygens or nitrogens. The wells are located at the atomic shells. The transition probability or its inverse, the relaxation time, depen ds exponentially on the barrier height and for a tunneling transition it depends also on the distance between the wells. The barrier height increases with increasing distance. Therefore the distribution of inte ratomic nearest neighbour distances in the amorphous state causes the distribution of dielectric relaxation times. The model is confirmed by experiments using palladium instead of gold electrodes. The palladium absorbs hydrogen from the atmosphere and enhances the density of prot ons in the dielectric resulting in an increase of the polarization str ength. This is shown here for thermally grown siliconoxide and electro n beam evaporated aluminumoxide.