Thermal behavior of hydrogen retained in amorphous-titanium-hydride thin films

Changes in hydrogen distribution near the surface of non-stoichiometric titanium hydride (TiH_x; x=0.49) thin films possessing an amorphous structure and approximately 170 and 400 nm thick, prepared by a magnetron ion-sputtering device, were investigated by combining an elastic recoil detection (ERD) technique with Rutherford backscattering spectrometry (RBS) one after isochronal annealing at different temperatures (300-500 K) for 10 min. The concentration of hydrogen atoms retained in TiHx thin films completely vanished at much lower temperatures of 350-400 K, as compared with the decomposition temperature (approximately 473 K) of δ-phase titanium hydride (δ-TiH_1.92). In addition, the thickness of TiH_x thin films also reduced with an increase in temperature. The rapid decrease of the hydrogen concentration in TiH_x thin films below 400 K is caused by thermal desorption of hydrogen atoms, detrapped from the amorphous structure and associated, in addition, with Ti evaporation.