Electrical resistivity and hydrogen solubility of PdHc thin films

During hydrogen gas loading, Pd thin films exhibit an anomalous reduction of resistivity change with decreasing film thickness. In this paper we show that this effect can mainly be attributed to a stress-dependent reduction of hydrogen solubility at a given hydrogen pressure. Different stress states of the thin films result from different bonding to a rigid substrate. Strongly buckled thin films show bulk-like pressure-resistivity isotherms. The resistivity changes as a function of hydrogen concentration appear to be independent of film thickness. The apparent Sieverts' constant seems to be larger for thin films compared to bulk, and increases with cycling of the thin films. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.