Ti 2p Lines Research Articles

Liquid-Jet X-ray Photoelectron Spectra of TiO(2) Nanoparticles in an Aqueous Electrolyte Solution.

Titania has attracted significant interest due to its broad catalytic applications, many of which involve titania nanoparticles in contact with aqueous electrolyte solutions. Understanding the titania nanoparticle/electrolyte interface is critical for the rational development of such systems. Here, we have employed liquid-jet ambient pressure X-ray photoelectron spectroscopy (AP-XPS) to investigate the solid/electrolyte interface of 20 nm diameter TiO2 nanoparticles in 0.1 M aqueous nitric acid solution. The Ti 2p line shape and absolute binding energy reflect a fully oxidized stoichiometric titania lattice. Further, by increasing the X-ray excitation energy, the difference in O 1s binding energies between that of liquid water (O 1sliq) and the titania lattice (O 1slat) oxygen was measured as a function of probe depth into the particles. The titania lattice, O 1slat, binding energy decreases by 250 meV when probing from the particle surface into the bulk. This is interpreted as downward band bending at the interface.

Structural and electrical properties of magnetron sputtered Ti(ON) thin films: The case of TiN doped in situ with oxygen

Incorporation of oxygen into TiN lattice results in formation of titanium oxynitrides, TiOxNy that have become particularly interesting for photocatalytic applications. Elaboration as well as characterization of TiN and in situ oxygen-doped thin films is the subject of this paper. Thin films, 250–320nm in thickness, have been deposited by dc-pulsed magnetron reactive sputtering from Ti target under controllable gas flows of Ar, N2 and O2. Optical monitoring of Ti plasma emission line at = 500nm has been implemented in order to stabilize the sputtering rate. Scanning electron microscopy (SEM), X-ray diffraction in grazing incidence (GIXRD), micro-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), optical spectrophotometry and four-point probe electrical resistivity measurements have been performed in order to follow evolution of film physical parameters as a function of the oxygen flow rate O2 at which the films were deposited. The relationship between O2 expressed in standard cubic centimetres per minute, sccm and the nitrogen/oxygen content in thin films has been established by means of the analysis of the XPS spectra. GIXRD studies indicate that incorporation of oxygen results in a progressive loss of preferential orientation in 111 direction, a change in the grain size from 16nm for TiN to about 3 nmfor films deposited at O2 = 1.32 sccm and a decrease in the lattice constant. A systematic shift of all X-ray diffraction (XRD) lines towards higher diffraction angles is consistent with substitution of oxygen for nitrogen. Micro-Raman investigations indicate amorphisation of thin films upon oxidation. Binding energies determined fromfitting of the XPS results concerning the N1s and Ti2p lines give evidence of the presence of TiOxNy compound. Red-shift of the plasma reflectance edge upon TiN oxidation is correlated with a decreased carrier concentration. Metal–semiconductor transition can be expected on the basis of the electrical conductivity decrease and development of the fundamental absorption across the forbidden band of TiO2 upon increase in the oxygen flow rate. Additional absorption feature in the visible range, being a consequence of coexistence of free-electron and interband absorption within almost the same spectral range ( = 400–600 nm) seems to be very promising for photocatalytic applications of titanium oxynitride thin films.

X-ray photoelectron spectroscopy study on sintered Pb 1− xLa xTiO 3 ferroelectric ceramics

The Pb 1− x La x TiO 3 sintered ferroelectric ceramics with x equal to 0, 0.10, 0.15, 0.20, and 0.30 were studied by X-ray photoelectron spectroscopy (XPS). The binding energy of the Ti 2p lines is consistent with only one chemical state, Ti 4+. On the other hand, in the case of Pb 4f and O 1s XPS spectra, apart from the main peaks attributed to the lattice ions, minor peaks related to the surface states were also observed. The presence of Pb 0 state on the surface of all samples was due to the reduction of lead ions caused by the preferential removal of the oxygen ions after sputtering. The non observation of Ti 3+ ions confirms that the mechanism of charge compensation that should occurs owing to the substitution of Pb 2+ by La 3+ is due to the preferential formation of Pb site vacancies, and not to a reduction from Ti 4+ to Ti 3+ states. Within the limits of the present experiment, there is no evidence of the existence of non-equivalent Pb, Ti, and La sites as the Pb 1− x La x TiO 3 ceramic changes from a normal to a relaxor ferroelectric state.

Effect of thermal annealing on the optical properties and residual stress of TiO_2 films produced by ion-assisted deposition

The effects of thermal annealing of titanium oxide films deposited by ion-beam assistance at annealing temperatures from 100 degrees C to 300 degrees C on the residual stress and optical properties of the films was investigated. The refractive indices and extinction coefficients increased gradually as the temperature was increased from 100 degrees C to 200 degrees C and then declined gradually as the temperature was increased further from 200 degrees C to 300 degrees C. The film lost oxygen and slowly generated lower suboxides as the annealing temperature was reduced below 200 degrees C, as determined by x-ray photoelectron spectroscopy (XPS). As the annealing temperature increased above 200 degrees C, the lower suboxides began to capture oxygen and form stable oxides. XPS measurements were made to verify both the binding energy associated with the Ti 2p line and the variation of the O 1s line. A Twyman-Green interferometer was employed for phase-shift interferometry to study the residual stress. The residual stress declined as the temperature was reduced from 100 degrees C to 200 degrees C because the lower suboxides reduced the stress in the film. Above 200 degrees C, the film began to capture oxygen, so the residual stress rose. At 300 degrees C, the film was no longer amorphous as the anatase was observed by x-ray diffraction.

Amorphous TiO 2 in LP-OMCVD TiN xO y thin films revealed by XPS

TiN(O)–TiO 2 thin films were prepared on Si(1 0 0) by the low pressure organo metallic chemical vapor deposition (LP-OMCVD) method, using ammonia and titanium isopropoxide as precursors. In order to complete previous characterizations, an Ar + bombardment/XPS coupled study was carried out. This method is based on the fact that the behavior of a compound towards an ion bombardment is a function of its composition. In particular, Ar + bombardment of TiO 2 (whatever its form) leads to a preferential sputtering of oxygen atoms with subsequent reduction of titanium and formation of Ti 3+ and Ti 2+ easily detectable by XPS from a significant broadening of the Ti 2p lines. In the opposite, no broadening of the Ti 2p lines is observed for an Ar + bombardment of TiN. Then, with this method, we succeed in showing that films obtained at high temperature (≥700°C) contain only a TiN x O y phase which is isomorphic to TiN. In the coatings, synthesized at low temperatures (≤650°C) amorphous TiO 2 has been evidenced.

Surface chemical changes in PVD TiN layers induced by ion bombardment

AbstractTiN layers produced by the PVD method were subjected to bombardment by different ion species applied in sequence. The relative atomic concentration and the chemical states of the elements in the surface layer were determined by means of x‐ray photoelectron spectroscopy. The composition and chemical states of a reference sample after wet chemical etching were taken to be representative for the stoichiometric TiN not affected by ion sputtering. For this sample characteristic line energies of Ti 2p3/2 = 454.7 eV and N 1s = 396.7 eV were found. Alternate bombardment with Ar+, N2O+ ions (1–5 keV) results in significant compositional and chemical state changes. Ar+ bombardment leads to preferential loss of N from the outermost (1–3 nm) surface layers of the nearly stoichiometric TiNx (x = 1.0–1.1) without observable changes in the chemical state of the constituents. Bombardment with N2+ ions leads to a build‐up of excess N (x ≫ 1) followed by the appearance of new N 1s and Ti 2p lines at 395.8 ± 0.3 eV and at 456.3 ± 0.3 eV, respectively. N2O+ bombardment increases the O and decreases the N concentration together with a concomitant shot out of a Ti 2p3/2 component peak at about 457.6 eV assignable to Ti2O3.

Influence of the deposition parameters on the composition, structure and X-ray photoelectron spectroscopy spectra of TiN films

The composition, structure and electronic structure of TiN films synthesized by the arc method have been studied by means of X-ray photoelectron spectroscopy (XPS) and electron microscopy. Dependences of the film composition and structure on the deposition parameters (working gas pressure, potential and temperature of the substrate, cathode current) were obtained. Also established was the dependence of the binding energy changes of the Ti 2p and N 1s core electron levels and valence band on the nitrogen content in nitride films. With increasing nitrogen concentration, the XPS Ti 2p line was found to be chemically shifted toward higher binding energies (from 454.1 eV for titanium to 455.2 eV for TiN 0.81), which provides evidence that, during TiN x formation, the positive effective charge on titanium atoms increases.

Surface composition and structure of titanium glasses

The surface of titanium glasses and quartz has been studied by X-ray photoelectron spectroscopy (ESCA) using both vacuum and temperature changes as a method of inducing structural changes. For the system the Si 2p, Si 2s, Ti 2p and O 1s binding energies have been characterized and distinct chemical shift of Ti 2p line for glasses has been detected. From quantitative data the chemical reduction of the surface of surface clusters was assumed and the size of clusters was determined. From the position of satellite lines in spectra the widths of the band gap for glasses has been obtained.