Search results for "Titan"
showing 10 items of 1109 documents
Resistive switching in microscale anodic titanium dioxide-based memristors
2018
Licence CC BY-NC-ND The potentiality of anodic TiO2 as an oxide material for the realization of resistive switching memory cells has been explored in this paper. Cu/anodic-TiO2/Ti memristors of different sizes, ranging from 1 × 1 μm2 to 10 × 10 μm2 have been fabricated and characterized. The oxide films were grown by anodizing Ti films, using three different process conditions. Measured IV curves have shown similar asymmetric bipolar hysteresis behaviors in all the tested devices, with a gradual switching from the high resistance state to the low resistance state and vice versa, and a R_OFF/R_ON ratio of 80 for the thickest oxide film devices.
Donor–Acceptor Interfaces by Engineered Nanoparticles Assemblies for Enhanced Efficiency in Plastic Planar Heterojunction Solar Cells
2016
Precisely positioning functionalized gold nanoparticles assemblies at planar donor-acceptor interfaces results in 14-fold enhancement of power conversion efficiency in P3HT/PCBM organic solar cells on plastic (ITO/PET) substrates. This result has been achieved by employing naphthalenethiol-capped gold nanoparticles (NT-Au-NPs) produced by laser ablation in liquid and size varied in the 10-30 nm range. Upon surface functionalization with the aromatic thiol, these particles self-assemble in submicrometer aggregates, which give increased light scattering. When these aggregates are deposited in the planar heterojunction between the donor and the acceptor systems, the localized scattering leads …
Investigation of pitting resistance of titanium based on a modified point defect model
2011
Abstract The pitting resistance of titanium was studied under potential control in solutions containing chloride ions. The results evidenced that Cl − concentration had an effect on the metastable pitting intensity, but no significant influence on the uniform corrosion. XPS characterization revealed that some Cl − ions were present in the outer hydroxide layer, but few in the inner oxide layer, indicating that the inner oxide layer was impervious to Cl − ions. A cation–anion-vacancy condensation mechanism was considered for pit initiation based on the point defect model (PDM). The experimental results analyzed by the charge integration technique were in agreement with the derived relations.
Evaluation of metastable pitting on titanium by charge integration of current transients
2010
Abstract The metastable pitting of titanium has been studied under potentiostatic control in solutions containing chloride ions. An approach based on the charge integration of current transients was proposed for a quantitative determination of metastable pitting. A pit density (dmpit) was defined as the number of metastable pits per unit area per unit time (cm−2 h−1) with a typical size, instead of a size distribution. The calculated dmpit of titanium at 0.5 VSCE in 0.6 M NaCl was about 1.0 × 103 cm−2 h−1 with a typical radius of 0.12 μm. An exponential potential dependence of dmpit was obtained through the integration approach.
Investigation on passivity of titanium under steady-state conditions in acidic solutions
2011
Abstract The passivity of titanium was studied using potentiostatic polarization combined with Mott–Schottky analysis in acidic solutions. The oxide layer was characterized as an n-type semiconducting, oxygen deficient oxide (TiO1.993–1.996) with a donor density in the range of 1019–1020 cm−3 depending on electrode potential and electrolyte pH. The calculated thickness for the inner oxide layer was in the range of 1–4 nm, increasing linearly with applied potential and exponentially with electrolyte pH. The potential- and pH-dependence of the inner oxide thickness was interpreted by a modified point defect model for the migration-controlled oxide growth, in which the rate-determining step in…
Far infrared absorption by acoustic phonons in titanium dioxide nanopowders
2006
We report spectral features of far infrared electromagnetic radiation absorption in anatase TiO2 nanopowders which we attribute to absorption by acoustic phonon modes of nanoparticles. The frequency of peak excess absorption above the background level corresponds to the predicted frequency of the dipolar acoustic phonon from continuum elastic theory. The intensity of the absorption cannot be accounted for in a continuum elastic dielectric description of the nanoparticle material. Quantum mechanical scale dependent effects must be considered. The absorption cross section is estimated from a simple mechanical phenomenological model. The results are in plausible agreement with the absorption b…
Refractory metal reactivity towards oxide surface : W/TiO2(1 1 0) case.
2006
International audience; Reactivity of deposited tungsten towards TiO2(1 1 0) surface was studied using synchrotron radiation photoemission spectroscopy (both core levels, valence band and resonant photoemission) on Materials Science Beamline at ELETTRA. W depositions carried out at room temperature on TiO2(1 1 0) surface give rise to an interfacial reaction which leads to a metastable situation due to kinetic limitations. Annealing induces chemical changes which are function of the initial coverage; for fractional coverage, annealing induces completion of oxidation of deposit whereas reduction to metallic tungsten occurs for highest coverage. These results demonstrate that interaction of W …
Structure and chemical bonds in reactively sputtered black Ti–C–N–O thin films
2011
The evolution of the nanoscale structure and the chemical bonds formed in Ti–C–N–O films grown by reactive sputtering were studied as a function of the composition of the reactive atmosphere by increasing the partial pressure of an O2+N2 gas mixture from 0 up to 0.4 Pa, while that of acetylene (carbon source) was constant. The amorphisation of the films observed by transmission electron microscopy was confirmed by micro- Raman spectroscopy, but it was not the only effect associated to the increase of the O2+N2 partial pressure. The chemical environment of titanium and carbon, analysed by X-ray photoemission spectroscopy, also changes due to the higher affinity of Ti towards oxygen and nitro…
High Photoluminescence Quantum Yields in Organic Semiconductor-Perovskite Composite Thin Films.
2017
One of the obstacles towards efficient radiative recombination in hybrid perovskites is a low exciton binding energy, typically in the orders of tens of meV. It has been shown that the use of electron-donor additives can lead to a substantial reduction of the non-radiative recombination in perovskite films. Herein, the approach using small molecules with semiconducting properties, which are candidates to be implemented in future optoelectronic devices, is presented. In particular, highly luminescent perovskite-organic semiconductor composite thin films have been developed, which can be processed from solution in a simple coating step. By tuning the relative concentration of methylammonium l…
Peculiarities of photoluminescence of Al2O3 bulk and nanosize powders at low temperatures
2011
Abstract Photoluminescence has been studied in the aluminum oxide (Al2O3) bulk and nanosize powders in the 300–8 K temperature range. In both samples luminescence spectrum is characterized by presence of broad blue and red bands caused mainly by emission from the uncontrolled titanium impurity. At low temperatures luminescence intensity increases by several times and the red band obtains fine structure. The nature of the fine structure is discussed suggesting manifestation of splitting of the Ti3+ emitting level due to Jahn–Teller effect or overlapping of Ti3+ emission band with narrow lines from other emitting ions. The observed differences in low-temperature spectral features of nanopowde…