We calculated the mobility of two-dimensional electron gas along an n-type interface in LaAlO3/SrTiO3 heterostructure using the linearized Boltzmann equation. By solving the Schrödinger equation with the Poisson equation self-consistently, it was found that the interface remained non-conducting up to four unit cells of LaAlO3 film. For five or higher unit cells, the interface became conducting due to the significant overlap between the SrTiO3 conduction band and the LaAlO3 valence band. The electron gas was localized within 7 nm from the interface and multi-subbands were occupied. The calculated mobility matches reasonably well with available experimental data. It was found that the mobility is limited by the remote ionic charged layers in LaAlO3 at low temperature. At high temperature, the polar optical phonon was found to be the dominant scattering center.

Indium oxide doped with tin oxide, or ITO, has been widely used as an electrode material for flat panel displays. However, the rare metal in ITO is a limited natural resource. We succeeded in developing a material composed solely of elements with abundant reserves. We present the results of analyzing the electronic structure of an Mg-based compound based on its electrical conductivity. Mg-C thin films were prepared by sputtering method. A new transparent and electrically conductive material, Mg(OH)2-C, was formed after reacting the Mg-C film with moisture in air. On average, its transmittance of visible light was 90%. The mechanism for the effect of carbon on the electrical conductivity of Mg(OH)2 was examined on the basis of XPS spectra and DV-Xa molecular orbital calculations. The value of the band gap shows that Mg(OH)2 is an insulator. It was revealed that a new orbital appears when the number of substituting carbon atoms increases in the Mg(OH)2 lattice. It was possible to measure the new orbital that consisted of C-2s and C-2p. In addition, a comparison between the calculated electronic state around the valence band and the result measured by XPS of the obtained film reveals that they are in extremely close agreement.

In the present study we have synthesized Ni/NiO nanocomposite was synthesized via microwave assisted rapid chemical route. The electrochemical properties of the composite was studied and found to be showing better performance in presence of metallic nickel in presence of its oxide.

A novel microwave-assisted synthesis technique was used for the rapid preparation of nanocrystalline ZnGa2O4 at two different temperatures. The crystalline spinel oxide is formed at temperatures as low as 100 o C within few minutes, at a high yield of 96%, requiring no post-synthesis annealing. The as-prepared samples are polycrystalline and phase-pure as verified by XRD, with a crystallite size of ∼5 nm. Polycrystalline ZnGa2O4 substituted with Mn2+, Cr3+, Cu2+, and Co2+ was also similarly prepared. All samples are highly monodispersed, as measured by TEM. The ZnGa2O4 nanocrystals without further surface modification can be readily dispersed in chloroform to form a fully transparent colloidal solution, using which the bandgap of ZnGa2O4 was determined to be ~4.5 eV. The entire synthesis procedure, including solution preparation, microwave irradiation, and centrifugation takes about 30 minutes, which is faster than any procedure reported for a complex oxide like ZnGa2O4, as well as one with a small thermal budget. Photoluminescence shows a broad emission extending from 330 nm to 800 nm, which is surmised to be due to the defect structure in the oxide produced.

We report the properties of MgO:Si film as a protective cathode material on the electrical discharge, and the electronic state of the outer-most surface on MgO:Si film characterized by helium Meta-stable De-excitation Spectroscopy (MDS) and that of several nanometer region from the surface evaluated by X-ray Photoelectron Spectroscopy (XPS). Both of the spectra are discussed focusing on the dependence upon the amount of Si in the MgO film for understanding discharge phenomena. The analyses of the experimental data imply that the discharge properties are not improved due to surface degradation with the increase of Si in MgO films. However, an in-situ discharge experiment, in which MgO:Si films are not exposed for the atmosphere after its deposition, shows that the introduction of Si up to about 1 atomic% has the potential to enhance the secondary electron emission coefficient.

Vertically oriented, highly dense ZnO nanowires (NWs) array was successfully grown on both glass and silicon substrates using hydrothermal technique. A systematic study was carried out to investigate the effects of growth parameters including growth time and thickness of ZnO seed layer on the quality of ZnO NWs in terms of their homogeneity and orientation in the vertical direction. The diameter as well as the length of grown ZnO NWs was found to be closely dependent on the thickness of the pre-coated ZnO seed layer. The structures of ZnO NWs and electron-beam evaporated AgGa0.5In0.5Se2 (AGIS) thin film have been characterized by X-ray diffraction measurements and optical properties were measured by transmission measurement. The optic band gap of AGIS thin film was found to be almost optimum (1.56 eV) to match the abundant part of solar cell spectrum. AGIS thin film was deposited on the synthesized ZnO NWs to form p-n heterojunction based inorganic solar cell, which exhibited photovoltaic behavior with a power conversion efficiency of 0.37 % under A.M (1.5) illumination.

The intercluster interactions of iron/iron oxide core shell nanoclusters have been investigated, and their dependence on cluster size (d) has been discussed. A cluster deposition system is used to prepare core-shell nanoclusters with different d, varying from 9 to 14 nm.Transmission Electron Microscopy has been used for physical characterization, and Vibrating Sample Magnetometer for magnetic study. The cluster – cluster interactions have been investigated by field dependent isothermal remanent magnetization (IRM) and dc demagnetization (DCD) measurements at room temperature. Henkel plot shows more negative deviation from non- interacting case for bigger size nanoclusters than smaller size clusters.

We have examined the intrinsic surface physical property of a CrO2 thin film by means of surface sensitive photoemission spectroscopy. Epitaxial thin film of CrO2(100) has been grown on TiO2(100) by a closed chemical vapor deposition method using a Cr8O21 precursor. Low-energy electron diffraction (LEED) observations find that epitaxial growth of rutile-phase CrO2 occurs to the top monolayer of the film. Surface sensitive x-ray photoemission spectroscopy (XPS) measurements show a finite intensity in the region of the Fermi energy. The result evidences that the physical nature of near topmost layer of CrO2 thin film is metallic. Progress of understanding of the surface physical property of CrO2 thin film helps not only perform a reliable photoemission study to understand the physics of ferromagnetic metal in CrO2, but also develop the CrO2-based devices using a half-metallic nature for spintronics applications.

We report the growth of sheet-like nanostructured tungsten trioxide hydrate (3WO3·H2O) film on fluorine doped tin oxide (FTO) substrate via a facile crystal-seed-assisted hydrothermal method by using CH3COONH4 as capping agent. Dense thin film composed of irregular blocks with smaller surface area was obtained without the addition of CH3COONH4. X-ray diffraction (XRD) studies indicated that both films were of orthorhombic structure. The nanosheet film grown with CH3COONH4 after dehydration showed highly improved photocatalytic activities than the nanoblock one. The maximum anodic photocurrents of 1.16 mA/cm2 for oxidization of methanol and 0.5 mA/cm2 for water splitting were obtained for the nanosheet film with a highest photoconversion efficiency of about 0.3% under simulated solar illumination.

Large variation in basic memory properties is a serious issue that hinders the practical use of ReRAM. This study revealed that one of the main factors causing variation is the presence of multiple filaments which have distinct set voltages in each memory cell. An operating filament switches to another filament having the smallest set voltage at each instant of switching. We propose a resistive switching model that takes the presence of multiple filaments into consideration. A Monte Carlo simulation based on the resistive switching model reproduces the set voltage distribution. Improvement of accuracy of the simulation can be also expected considering the fact that V set increases at a certain probability at each instant of set switching.

Copper oxide (CuO) and zinc oxide (ZnO) nanostructures complement each other since CuO is unintentional p-type and ZnO unintentional n-type. Using the low temperature chemical growth approach, the effect on morphology of varying the pH of the grown ZnO nanostructures and CuO micro structures is monitored. For both materials the variation of the pH was found to lead to a large variation on the morphology achieved. The grown ZnO NRs and CuO micro flowers material were used to fabricate devices. We demonstrate results from ZnO nanorods (NRs)/polymer p-n hybrid heterojunctions chemically grown on paper and using a process on paper for light emitting diodes (LEDs) applications as well as some large area light emitting diodes LEDs. The growth of CuO micro flowers indicated good quality material for sensing applications. The grown CuO micro flowers were employed as pH sensors. The results indicated a superior performance as expect due to the catalytic properties of this material.

Bulk structures of un-stabilized ZrO2-x with x in the 0 ≤ x ≤ 0.44 range under ambient pressure exist in three different structures (monoclinic, tetragonal and cubic). At ambient temperature and elevated pressures above 3.5 GPa, zirconia, at these compositions, a fourth phase is found, the orthorhombic structure. A dilute sol-gel method was used to produce nanoscale zirconia particles containing the unstabilized orthorhombic cotunnite structure for use in this project. Extensive characterization of this material indicates that the critical factor in determining the synthesized structures appears to be the number and placement of oxygen vacancies. These results also indicate that surface energy alone is not the controlling factor in determining the crystal structure synthesized.

In this work, we studied metal/SnO2 junctions using transport properties. Parameters such as barrier height, ideality factor and series resistance were estimated at different temperatures. Schottky barrier height showed a small deviation of the theoretical value mainly because the barrier was considered fixed as described by ideal thermionic emission-diffusion model. These deviations have been explained by assuming the presence of barrier height inhomogeneities. Such assumption can also explain the high ideality factor as well as the Schottky barrier height and ideality factor dependence on temperature.

For the first time, we have used a metal oxide-coated quartz crystal microbalance (QCM) to measure Cs+ adsorption onto illuminated and un-illuminated mesoporous TiO2 (m-TiO2) films by microgravimetric means in-situ. In the simplest case, such experiments yield two parameters of interest: K, the Langmuir adsorption coefficient and m max the maximum mass of adsorbate to form a complete monolayer at the m-TiO2-coated quartz crystal piezoelectric surface. Importantly, we have found that illumination of the m-TiO2 film with ultra bandgap light results in an increase in m max i.e. illumination allows for greater adsorption of substrate to occur than in the dark. Our studies also show that under illumination, K also increases indicating a higher affinity for surface adsorption. The photoinduced change in m max and K are thought to be due to an increase in surface bound titanol groups, thus increasing the number of available adsorption sites – and so providing evidence to support the notion of photoinduced adsorption processes in photocatalytic systems. These findings have implications for the development of a reversible adsorption based microgravimetric sensor for Cs+.

Facile and direct synthesis of radiative VO2 (M) plate-like is reported. The snowflake material presents superstructures plate-like aggregate with an anisotropic orientation in shape governed by V2O5 and NaOH concentration giving high surface energy liable for chemical reactions with the medium. Pure crystalline VO2 (M) has been obtained with a complete hydrothermolysis of the precursor. The morphological, structural, elemental composition, crystallinity and vibrational bands of the powders were characterized by Powder X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Selected Area Electron Diffraction (SAED) and Fourier Transform-Attenuated Total Reflection (FTIR-ATR) infrared spectroscopy.

Magnetically separable and reusable core-shell CoFe2O4-ZnO photocatalyst nanospheres were prepared via hydrothermal synthesis technique using glucose derived carbon nanospheres as template. The morphology and phase of core-shell hybrid structure of CoFe2O4-ZnO was assessed via TEM, and XRD. The UV-vis photocatalytic activity of the composite was assessed via measuring the degradation rate of modeled pollutant methylene blue in water. The magnetic composite showed high UV photocatalytic activity for the degradation of methylene blue. The photocatalytic activity was found to be ZnO shell thickness dependent. Thicker ZnO shells lead to higher rate of photocatalytic activity. Hybrid nanospheres recovered using external magnetic field demonstrated good repeatability of photocatalytic activity. These results promise the reusability of hybrid nanospheres for photocatalytic activity.

With interface sizes rapidly reducing to the nanometer scale, it has become vital to understand how size and structure can affect transport behavior between materials in order to tune the energy barrier for various applications. Here, the fabrication of Schottky Barriers between Au nanoparticles and doped SrTiO3 materials is reported. The effect of nanoparticle size on the transport properties is clearly evident providing an excellent opportunity to compare new theory on transport characteristics at the nanoscale to classical theory to determine the method that is most effective in predicting nanoscale transport properties.

In our previous work, low resistance state (LRS) and high resistance state (HRS) areas on a nickel-oxide (NiO) film formed by applying a voltage using conductive atomic-force microscopy (C-AFM) was observed by scanning electron microscope (SEM). Comparing the observed secondary electron image (SEI) contrast to the report about the dopant-type dependence of SEI contrast reported on silicon, it was suggested that the LRS and HRS areas are, respectively, electrochemically induced p-type Ni1-xO (x > 0) and intrinsic (stoichiometric) or ntype Ni1-xO (x ≤ 0). In this paper, we verified that resistance change caused by C-AFM is due to electrochemically induced carrier injection. Reduction effect of H2 annealing on the writing area, voltage dependence of depletion layer capacitance formed between the writing area and AFM-tip using scanning nonlinear dielectric microscopy (SNDM), and the effect of Schottky barrier formation between the writing area and thin metal layer on SEI contrast were investigated. Based on these results, it was clarified that the LRS and HRS areas are, respectively, p-type Ni1-xO (x > 0) and intrinsic (stoichiometric) or n-type Ni1-xO (x ≤ 0)

Ceria has been aggressively explored for applications as a fuel cell electrolyte or in catalytic converter due to its high oxygen ion conductivity, or as a UV absorption material. It is proven that the properties and applications of ceria nanoparticles are related to their morphologies and sizes. This ability to control the shape and morphology of CeO2 nanoparticles allows the corresponding tuning of their chemical and physical properties. Most of the applications require the use of non-agglomerated nanoparticles, as aggregated nano-particles lead to inhomogeneous mixing, poor sinterability and compromised properties. However, nano-crystals with a primary particle size < 5 nm have a strong tendency to agglomerate. In this work, nano-crystalline particles of CeO2 have been synthesized by a low temperature hydrothermal and solvent thermal synthesis process. Using the precursors of Ce(NO3)3.6H2O:NaOH in different mixing ratio, using polyvinylpyrrolidone (PVP) as the surfactant, the CeO2 particles were synthesized via 24 h hydrothermal and solvent thermal process treatment at reaction temperature of 100 °C and 180 °C using Teflon-lined hydrothermal autoclave. We have optimized the conditions for the two synthesized methods, hydrothermal and solvent thermal, to yield highly crystallized particle with controllable shape, sizes and morphology. X-ray diffraction (XRD) and high-resolution transmission electron microscope (HR-TEM) analysis were used to characterize the crystalline and morphology of the synthesized CeO2 nanoparticles. The optimal reaction condition to prepare the CeO2 of the desired octahedron shaped fluorite structure was established. Based on the results, the hydrothermal synthesis method yields nanocrystalline CeO2 sizes of ∼6 nm, while the solvent synthesis method yields nanocrystalline CeO2 sizes of 2-3 nm at the optimal conditions. The hydrothermal synthesis method produced better particles in terms of crystallinity and morphology under HR-TEM. Temperature also plays a part in crystallinity and sizes of the CeO2 nanoparticles. The crystallinity and size of the CeO2 nanoparticles increases when using higher treatment temperature for both hydrothermal and solvent thermal methods. The growth mechanism of the shape and morphology of the CeO2 will also be discussed.