About the defect structure in differently doped PZT ceramics: A temperature dependent positron lifetime study

Pure and doped PZT ceramics (PZT:La+Fe, PZT:La, PZT:Gd, PIC 151 and with 0.1, 0.25, 0.5, 1.0 mol% Fe doped samples) have been examined by Positron Annihilation Lifetime Spectroscopy (PALS) in the range of temperatures between 150 and 375 K. It was found that the defect-related lifetime increased with increasing temperature, indicating vacancy-like defects. With increasing Fe doping, a loss of vacancy agglomerations was observed, as well as a weaker dependence of lifetime on temperature

Diffusion and chemical composition of TiNxOy thin films studied by Rutherford Backscattering Spectroscopy

Thickness and chemical composition of the TiNxOy thin films deposited by reactive magnetron sputtering from Ti target at controllable oxygen flow rate were determined by Rutherford Backscattering Spectroscopy (RBS) using 2 MeV He+ ions. The films were deposited on carbon foils and amorphous silica (a-SiO2) substrates at 25 °C and 250 °C. The estimated film thickness is of 75-100 nm. The O/Ti atomic ratio in the films increases up to 1.5 with increasing oxygen flow rate, while that of N/Ti decreases from about 1.1 for TiN to 0.4 at the highest oxygen flow rate. Substantial out-diffusion of carbon from the substrate is observed which is independent of the substrate temperature. Films grown onto a-SiO2 substrates can be treated as homogeneous single layers without interdiffusion. It is more difficult to determine the nitrogen and oxygen content due to superposition of RBS signals arising from film and substrate. RBS analysis of the depth profile indicates that for the investigated films the carbon diffusion and oxidation not only at the topmost surface layers but over the bulk of the films were found. Comparison with XPS results indicates substantial oxygen adsorption at the surface of TiNx thin films obtained at zero oxygen flow rate

Hydrogen storage in Ti, V and their oxides-based thin films

We have investigated the hydrogen storage ability and the effect of hydrogenation on structure and physical properties of Ti/V and their oxides-based thin films. A series of Ti-TiO2 and VO-TiO2 thin films with different layer structures, geometries and thicknesses have been prepared by the sputtering technique on different (Si(111), SiO2, C) substrates. For the Ti-TiO2-Ti films up to 50 at.% of hydrogen can be stored in the Ti layers, while the hydrogen can penetrate without accumulation through the TiO2 layer. A large hydrogen storage was also found in some V2O5-TiO2 films. Hydrogen could also remove the preferential orientation in the Ti films and induce a transition of V2O5 to VO2 in the films

Study of Ti, V and Their Oxides-Based Thin Films in the Search for Hydrogen Storage Materials

Thin film series consisting of Ti, V, TiO₂ and V₂O₅ layer with different layer geometries, sequences and thicknesses have been prepared by the sputtering technique. The hydrogen depth profile of selected films upon hydrogen charging at 1 bar and/or hydrogenation at pressure up to 102 bar was determined by using secondary ion mass spectrometry and nuclear reaction analysis using a N-15 beam. The highest hydrogen storage with a concentration up to 50 at.% was found in the pure Ti and Ti-contained layer, while it amounts to around 30% in the metallic Ti-V-Ni layer. Hydrogen can diffuse through the TiO₂ layer without accumulation, but can be stored in the VO₂ layer in some cases. Hydrogen can remove the preferential Ti orientation in the films and induce a complete transition of V₂O₅ into VO₂ in the films

RBS, XRR and optical reflectivity measurements of Ti-TiO2 thin films deposited by magnetron sputtering

Single-, bi- and tri-layered films of Ti–TiO2 system were deposited by d.c. pulsed magnetron sputtering from metallic Ti target in an inert Ar or reactive Ar + O2 atmosphere. The nominal thickness of each layer was 50 nm. The chemical composition and its depth profile were determined by Rutherford backscattering spectroscopy (RBS). Crystallographic structure was analysed by means of X-ray diffraction (XRD) at glancing incidence. X-ray reflectometry (XRR) was used as a complementary method for the film thickness and density evaluation. Modelling of the optical reflectivity spectra of Ti–TiO2 thin films deposited onto Si(1 1 1) substrates provided an independent estimate of the layer thickness. The combined analysis of RBS, XRR and reflectivity spectra indicated the real thickness of each layer less than 50 nm with TiO2 film density slightly lower than the corresponding bulk value. Scanning Electron Microscopy (SEM) cross-sectional images revealed the columnar growth of TiO2 layers. Thickness estimated directly from SEM studies was found to be in a good agreement with the results of RBS, XRR and reflectivity spectra

Hydrogen storage in Ti-TiO2 multilayers

Multilayered thin films of Ti-TiO2 system have been investigated, focusing on all of the important parameters in both photocatalysis and H storage. Numerous Ti-TiO2 thin films with a single-, bi- and tri-layered structure have been deposited on different substrates by means of dc pulsed magnetron sputtering from a metallic Ti target in an inert Ar or reactive Ar + O2 atmosphere. The film chemical composition, depth profile, layer thickness and structure were determined by combined analysis of x-ray diffraction, x-ray reflectometry, Rutherford back- scattering and optical reflectivity spectra. The results show that the Ti films deposited on Si(111) exhibit a strong preferred orientation with the (00.1) plane parallel to the substrate, while a columnar structure was developed for TiO2 films. H charging at 1 bar and at 300 °C revealed that, in the case of the tri-layered structure of Ti/TiO2/Ti/Si(111), H diffused through the TiO2 layer without any accumulation in it. Pd acts as a catalyst for gathering H in Ti layers and up to 50% of H is stored in the topmost and bottom Ti layers. The preferential orientation in the Ti films was found to be destroyed upon hydrogenation at 100 bar. The hydride TiHx phase (x < 0.66) was formed under such a high H pressure

Hydrogen content analysis in hydrogen-charged PZT ferroelectric ceramics

PbZrxTi(1 − x)O3 (PZT) ferroelectric ceramic samples have been charged with hydrogen at a temperature of 400 °C. The resulting hydrogen depth profiles have been determined both by secondary ion mass spectrometry (SIMS) and nuclear reaction analysis using the 15N beam (N-15 method) at and above the resonance energy of 6.4 MeV. After charging, the hydrogen concentration was found to be increased in the near surface region. The hydrogen concentration determined by the N-15 method revealed that the concentration decreased with increasing fluences. However, at higher fluences the remaining hydrogen concentration was constant and amounts to about half of the value estimated at the lowest fluence. Infrared spectroscopy measurements indicated the existence of a polar hydroxyl bond OH−

Hydrogen Charging Effects in Pd/Ti/TiO2/Ti Thin Films Deposited on Si(111) Studied by Ion Beam Analysis Methods

Titanium and titanium dioxide thin films were deposited onto Si(111) substrates by magnetron sputtering from a metallic Ti target in a reactive Ar+O2 atmosphere, 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 a 15N 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