Silicon dioxide based Electrochemical Metallization (ECM) cells were intensively studied as a promising candidate for CMOS compatible non-volatile memory devices. The resistance of ECM cells can be switched between a high resistive (OFF) state and a low resistive (ON) state by applying a sufficient voltage or current pulse. This resistance transition is attributed to the formation and rupture of a few nanometers in diameter metallic filament. However, the metal ion transport which is believed to be responsible for the filamentary switching mechanism is not understood in detail. In case of SiO2 we suppose protons or humidity may enhance the metal ion transport.

In this work we report our studies on the proton incorporation in amorphous SiO2 thin films focused on the impact of hydrogen and humidity on the resistive switching effect. The switching behavior was analyzed by current-voltage measurements performed at different ambient conditions. The incorporation of hydrogen has been confirmed by Time-of-Flight Secondary-Ion-Mass-Spectroscopy (ToF-SIMS). The results led to an expansion of the defect model proposed in the literature.

The dependence of Li mobility on structure and composition of quenched Li0.5-xNax La0.5TiO3 (0 ≤ x < 0.5) and slowly cooled Li0.2-xNaxLa0.6TiO3 (0 ≤ x < 0.2) perovskite series, has been investigated by means of Neutron Diffraction (ND), Nuclear Magnetic Resonance (NMR) and Impedance Spectroscopy (IS). The first series displays rhombohedral (√2ap, √2ap, 2√3ap; S.G. R-3c) symmetry and vacancies are randomly distributed on A-sites (disordered phases), while Li0.2-xNaxLa0.6TiO3 series, presents orthorhombic unit cells (2ap, 2ap, 2ap; S.G. Cmmm) and the vacancies are preferentially located in alternating layers along the c-axis (ordered phases). In both cases, Li ions are shifted from A sites to a fourfold coordination at unit cell faces of the single cubic perovskite and octahedral are tilted along the rombohedral axis in Li-rich and along b-axis in Li- poor series. By heating the elimination of the octahedral tilting takes place changing the symmetry from rhombohedral to cubic in Li-rich samples, and from orthorhombic to tetragonal in Li-poor samples; however no changes were detected in La-vacancy distributions. For a particular value of sodium content (x=0.3 for Li0.5-xNaxLa0.5TiO3 and x=0.17 for Li0.2-xNaxLa0.6TiO3), the conductivity drops several orders of magnitude indicating that the amount of vacancies approaches the percolation threshold. In the temperature range 77-500 K, conductivity of Na-doped samples displays departures from the Arrhenius behavior, decreasing activation energy from 0.37 to 0.25 eV in disordered samples and from 0.37 to 0.12 eV in ordered ones. The structural sites occupancy has been investigated by ND, while Li mobility was evaluated through NMR and Impedance spectroscopy. The temperature dependence of thermal BLi factors has been related to the increment of conductivity that precede structural transformations, suggesting that Li motion trigger detected transitions in both series.

We report an interesting property of carbon dots: they emit light under charge injection. We synthesized carbon dots in diameter about 20 nm using wet chemistry methods. The photoluminescence quantum efficiency of the carbon dots dissolved in water was about 11%. We observed strong electrogenerated chemiluminescence (ECL) from the sample. This observation of ECL from carbon dots indicates that they could be a good candidate material for carbon-based electroluminescent devices.

The large intrinsic band gap in TiO2 has hindered severely its potential application for visible-light irradiation. We have used a passivated approach to modify the band edges of anatase-TiO2 by codoping of X (N, C) with transition metals (TM=W, Re, Os) to extend the absorption edge to longer visible-light wavelengths. It was found that all the codoped systems can narrow the band gap significantly; in particular, (N+W)-codoped systems could serve as remarkably better photocatalysts with both narrowing of the band gap and relatively smaller formation energies and larger binding energies than those of (C+TM) and (N+TM)-codoped systems. Our theoretical calculations help to rationalise experimental results and provide reasonably meaningful guides for experiment to develop more powerful visible-light photocatalysts.

Microstructural characterization (Focused Ion Beam and Transmission Electron Microscopy imaging) was performed on cross-sections of contacts in thick Electro Chemical Deposition copper metallization of System In Package Integrated Circuits. It was shown that the lower growth rate of ECD-Cu in the AlSiCu – barrier Ti – PVD-Cu – ECD-Cu layer stacking is related to a local higher resistivity induced by the presence of a great number of almost planar grain boundaries in the PVD-Cu layer, which are perpendicular to the growth axis. This morphology is a consequence of the almost heteroepitaxial growth of Ti layer on AlSiCu layer.

Mechanical properties and thermal stability of bulk glassy alloys depend on their chemical composition ratios, although their detailed local structures especially around free volume have not been clarified yet. In order to know the origin of property dependence on alloy composition in Zr-Cu-Al ternary bulk glassy alloys in a view point of atomic scale, positron annihilation lifetime, coincidence Doppler broadening (CDB) and EXAFS (extended X-ray absorption fine structure) measurements have been employed for eutectic Zr50Cu40Al10 and hypoeutectic Zr60Cu30Al10 bulk glassy alloys before and after structural relaxation by annealing below glass transition temperature Tg .

The result of CDB experiment, which represents the electron momentum distribution around free volume, shows that significant atomic reordering around free volume does not take place by the annealing in each alloy. Besides, CDB ratio profiles for each alloy suggest that the fraction of Zr atom around free volume does not match the chemical composition of each alloy system. Change in positron lifetime, which is proportional to the size of free volume, during annealing for hypoeutectic alloy almost remains unchanged.

The effect of fine M2C particles on the recrystallization temperature and high temperature strength of warm rolled Fe3Al base alloys was investigated. Fe-27Al-1.2C-2Cr-xMo (x: 0.3, 0.9) alloys (in at.%) were arc melted, warm rolled and annealed. TEM observations have revealed that fine M2C particles were present in the alloy containing 0.9% Mo but not in the alloy with 0.3% Mo after warm rolling. The recrystallization temperature increased from 740 °C to 810 °C when the Mo content is increased from 0.3 to 0.9 due to the presence of fine M2C particles. Tensile tests conducted on annealed samples with fine sub-grained matrix have shown that the introduction of fine M2C particles is effective to enhance the proof stress at 600 °C.

We report on a combined structural and electronic analysis of niobium ultrathin films (from 2.5 to 10 nm) epitaxially grown in ultra-high vacuum on atomically flat sapphire wafers. We demonstrate a structural transition in the early stages of Nb growth, which coincides with the onset of a superconducting-metallic transition (SMT). The SMT takes place on a very narrow thickness range (1 ML). The thinnest superconducting sample (3 nm/ 9ML) has an offset critical temperature above 4.2K and allows to be processed by standard nanofabrication techniques to generate air and time stable superconducting nanostructures.

Amorphous Ta-N thin films (14 and 62 nm thick) are deposited on Si substrates by reactive magnetron sputtering followed by Cu film deposition. The interlayer reaction and failure mechanism of the annealed metallization stacks are investigated by resistance measurements, xray diffraction (XRD) and detailed electron microscopy analysis accompanied with electron energy-loss spectroscopy (EELS). Amorphous Ta-N crystallizes at 600°C by a polymorphous transformation to Ta2N. The crystallized Ta2N barrier prevents Cu-Si interaction and intermixing up to 700-800°C, depending on the barrier thickness. Copper appears to be the main diffusing species and reacts with Si at the Ta-N/Si interface to form η˝-Cu3Si. Local Cu-Si reaction enhances the formation of TaSi2 precipitates. Silicon also diffuses, though at a much slower rate, to the surface and reacts with Cu. Local oxidation of Cu3Si occurs upon exposure to air, accompanied by SiO2 formation.

The structure of irradiated material near a primary knock on atom shortly after impact is largely unknown. Molecular dynamics simulations with classical force fields provide the foundation for our current understanding of the resulting cascade. Atomic level structural characterization is often in terms defects within the context of a perfect bulk, however, the choice of the best representation is complicated because the density of defects is high, the material is inhomogeneous and it is not in equilibrium. Here we explore the adaptation of tools typically employed to characterize homogeneous equilibrium liquids to the highly defected region of the cascade. The cascade structure shows some resemblance to that of the liquid or glass phase. The local temperature temporarily exceeds the melting temperature and the free energies of the liquid and defected crystal are comparable. Analysis of cascade structure will be important to the interpretation of first principles calculations of the electronic and magnetic states in cascade structures.

Resonant cavity light emitting diode (RCLED) structure was grown using digital AlGaN/GaN Distributed Bragg Reflector (DBR) and Ag-based p-contact. A five period of InGaN/GaN multi-quantum well (MQW) layers are placed between these two high reflectance mirrors. Digital AlGaN/GaN DBR have a maximum reflectivity of about 60 % at 445 nm and 90 % at 439 nm for 6 period and 12 period, respectively. Ag-based p-contact exhibits an average reflectance of around 85-90 % for a wavelength of 400-600 nm. The light output intensity of the RCLEDs with 12 period digital AlGaN/GaN DBR is higher by a factor of 3 as compared to that of the similar structure without digital AlGaN/GaN DBR at an injection current of 50 mA.

There is widespread interest in developing efficient solar cells derived from conjugated polymers and TiO2. The conjugated polymer can act as a light harvesting dye as well as a hole transport material, and can potentially replace both the ruthenium dye and the I3 -/I- couple in the DSSCs. Herein, we report a novel and facile approach of using conjugated polymer nanoparticles to make conjugated polymer:TiO2 nanocomposite based solar cell. Nanoparticles from poly(3-hexylthiophene) (P3HT) were made using mini-emulsion technique. In this work we report on incorporation of these P3HT nanoparticles into nanoporous titania. Device characteristics made using P3HT nanoparticle sensitized solar cells were measured. These devices showed a short-circuit current density (Jsc) of 0.207 mA/cm2, open-circuit voltage (Voc) of 0.62 V and 0.07% (η) efficiency.

Recently, we have proposed a spin quantum cross structure (SQCS) device toward the realization of novel spintronics devices. In this paper, we have investigated thermoelectric effects in point contacts (PCs) of Ni ferromagnetic metals using SQCS devices, theoretically and experimentally. The calculated results show that the thermoelectric voltage Vq changes from 0.48 mV to 2.12 mV with the temperature difference of PCs increasing from 10 K to 50 K. Also, the magnitude of the theoretical thermoelectric voltage agrees very well with that of the experimental result. PCs of SQCS devices with Ni electrodes can serve as spin dependent thermobatteries.

Oxide-embedded Silicon nanoparticles (OE-Si-NPs) are of great interest for many applications due to unique size effects observed when their size drops below 5 nm (Silicon’s Bohr exciton radius). Some of the suggested applications require patterning of the nanoparticles in an ordered array. Lithographic methods to pattern Si-NPs are common in the literature, however these methods can be costly, and are not time-efficient. Recently, non-lithographic patterning techniques have become very attractive because they are cost-effective and straightforward. In this proceeding we will demonstrate non-lithographic patterning of OE-Si-NPs characterized via AFM and XPS.

We here present, metal nanocrystal (NC) formation statistics (size, density, occupancy or area coverage) on different high dielectric constant (high-K) materials which may be used as tunnel dielectric or intermetal dielectric in flash memory devices. Four important high-K materials viz. SiO2, Al2O3, HfO2 and Si3N4 are chosen for this purpose and the nanocrystal formation statistics has been found to be strongly dependent on dielectric. Among all the four dielectrics, smallest size nanocrystals with largest density are obtained on Al2O3 dielectric while on HfO2 bigger size nanocrystals are formed. This difference in nanocrystal size and density on different dielectrics is attributed to the different surface properties of these materials.