HYDROGEN DIFFUSION THROUGH THE SEMICONDUCTOR-LIQUID-JUNCTION ON TIO2 (RUTILE) ELECTRODES

Reduction of TiO//2 (rutile) single crystals with hydrogen at temperatures considerably higher than room temperature leads, in addition to the formation of oxygen vacancies, to crystal structures where hydrogen is chemically bound inside the crystal. Investigations on such crystals have revealed that bound hydrogen becomes sufficiently mobile at temperatures above 450 degree C so that it can leave the crystal. In contrast to that, the mobility of unbound interstitial hydrogen ions is much higher even at room temperature. It was shown that unbound interstitial hydrogen leaves the crystal by two different mechanisms: above an internal electric field strength, E//S, close to the surface of 10**6V cm** minus **1 as protons, whereas below that value as atoms.