RBS/channeling analysis of epitaxial Pt and Pd films irradiated with Co -ray

Yamamoto, Shunya; Shimada, Akihiko; Miyashita, Atsumi; Hakoda, Teruyuki

Platinum (Pt) and Palladium (Pd) have been used in solid-state hydrogen sensors as a catalysis which acts to dissociate hydrogen molecules into protons and electrons. To apply solid-state hydrogen sensors under -ray radiation, it is essential to understand the effects of -ray radiation on crystal structure of Pt and Pd. Rutherford backscattering spectrometry (RBS) combined with channeling has been used to examine crystal structure and composition of surface region. Thus, preparation of epitaxal films which can be analysis by RBS/channeling allow us to understand the influence of -ray radiation on structure of the thin films. In the present study, epitaxial Pt and Pd films were grown on sapphire substrates by an rf magnetron sputtering. The crystallographic orientation and surface chemical states were characterized by X-ray diffraction and X-ray Photoelectron Spectroscopy (XPS). RBS/channeling analysis was performed to characterize the epitaxial films by employing He ions with the energy of 2.0 MeV. The epitaxial films were irradiated with Co -ray ( 5 MGy) at RT in a sealed glass vessel in the air. The results of RBS and XPS suggest that enhanced oxidation of Pd films is related to nitric acid in air produced by -ray radiation.