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°C. Pure Ti samples were deposited in a high-vacuum condition, while for deuterated samples, deuterium high-purity gas was introduced in the deposition chamber during the process. Film composition was studied by Rutherford backscattering spectrometry (RBS) and elastic recoil detection analysis (ERDA), whereas structural characterization of the deposited layers was carried out by x-ray diffraction (XRD) using both the traditional Bragg-Brentano geometry and a parallel beam setup for pole figure measurements. Titanium films deposited in a high vacuum showed the hexagonal Ti structure (α - Ti) and grew with a double orientation at each of the examined substrate temperatures. Deuterated titanium films deposited at 150°C had a compositional ratio Ti:D = 1:0.35 and grew with a [111] oriented fcc structure, suggesting the formation at low temperature of a substoichiometric δ hydride phase. Deuterated films deposited at higher substrate temperatures revealed a lower deuterium content and XRD reflections corresponding to the hexagonal Ti phase. The present results were interpreted according to a temperature-dependent D2 adsorption mechanism at the surface of the continuously growing Ti film.