Abstract
Titanium and titanium dioxide thin films were deposited onto Si(111) substrates by magnetron sputtering from a metallic Ti target in a reactive Ar+O2atmosphere, the composition of which was controlled by precision gas controllers. For some samples, 1/3 of the surface was covered with palladium using molecular beam epitaxy. Chemical composition, density, and layer thickness of the layers were determined by Auger electron spectroscopy (AES) and Rutherford backscattering spectrometry (RBS). The surface morphology was studied using high-resolution scanning electron microscopy (HRSEM). After deposition, smooth, homogenous sample surfaces were observed. Hydrogen charging for 5 hours under pressure of 1 bar and at temperature of 300°C results in granulation of the surface. Hydrogen depth profile was determined using secondary ion mass spectrometry (SIMS) and nuclear Reaction Analysis (N-15 method), using a15N beam at and above the resonance energy of 6.417 MeV. NRA measurements proved a higher hydrogen concentration in samples with partially covered top layers, than in samples without palladium. The highest value of H concentration after charging was about 50% (in the palladium-covered part) and about 40% in titanium that was not covered by Pd. These values are in good agreement with the results of SIMS measurements.
Highlights
Titanium hydride films have many potential applications, for example, neutron super mirrors, hydrogen storage layers, and standards for hydrogen quantitative analysis
The results show a hydrogen concentration of over 50% in the titanium layer, meaning that probably the δ phase with FCC lattice has been achieved
Results of N-15 measurements show a high accumulation of hydrogen in the first titanium layer (∼40%) and a smaller amount in the second titanium layer (∼15%)
Summary
Titanium hydride films have many potential applications, for example, neutron super mirrors (multilayers of nickel and titanium employed for the transport of cold neutron beams), hydrogen storage layers, and standards for hydrogen quantitative analysis. Saturation of these systems with hydrogen improves their reflectivity, because hydrogen increases the difference between the two indices of refraction and allows one to diminish the number of layers needed [1]. Titanium dioxide top layers act as a protective layer (against corrosion) and as a barrier to hydrogen absorption into the metal [3]
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