Structural characterization of deuterated titanium thin films

Pure and deuterated titanium thin films 140 nm thick were deposited on (100 ) Si wafers by electron beam evaporation, keeping the substrate temperature at 150, 300, and 450 degrees C. Pure Ti samples were deposited in a high-v acuum condition, while for deuterated samples, deuterium high-purity gas wa s introduced in the deposition chamber during the process. Film composition was studied by Rutherford backscattering spectrometry (RBS) and elastic re coil detection analysis (ERDA), whereas structural characterization of the deposited layers was carried our by x-ray diffraction (XRD) using both the traditional Bragg-Brentano geometry and a parallel beam setup for pole figu re measurements. Titanium films deposited in a high vacuum showed the hexag onal Ti structure (a-Ti) and grew with a double orientation at each of the examined substrate temperatures. Deuterated titanium films deposited at 150 degrees C had a compositional ratio Ti:D = 1:0.35 and grew with a [111] or iented fee structure, suggesting the formation at low temperature of a subs toichiometric delta hydride phase. Deuterated films deposited at higher sub strate temperatures revealed a lower deuterium content and XRD reflections corresponding to the hexagonal Ti phase. The present results were interpret ed according to a temperature-dependent D-2 adsorption mechanism at the sur face of the continuously growing Ti film.