Interface formation of nanostructured heterojunction SnO 2:Eu/GaAs and electronic transport properties

Thin films of tin dioxide (SnO2) are deposited by the sol-gel-dip-coating technique, along with GaAs layers, deposited by the resistive evaporation technique. The as-built heterojunction has potential application in optoelectronic devices, combining the emission from the rare-earth doped transparent oxide (Eu3+-doped SnO2 presents very efficient red emission) with a high mobility semiconductor. The advantage of this structure is the possibility of separation of the rare-earth emission centers from the electron scattering, leading to a strongly indicated combination for electroluminescence. Electrical characterization of the heterojunction SnO2:Eu/GaAs shows a significant conductivity increase when compared to the conductivity of the individual films, and the monochromatic light irradiation (266 nm) at low temperature of the heterojunction GaAs/SnO2:Eu leads to intense conductivity increase. Scanning electron microscopy (SEM) of the heterojunction cross section shows high adherence and good morphological quality of the interfaces substrate/SnO2 and SnO2/GaAs, even though the atomic force microscopy (AFM) image of the GaAs surface shows disordered particles, which increases with sample thickness. On the other hand, the good morphology of the SnO2:Eu surface, shown by AFM, assures the good electrical performance of the heterojunction. The observed improvement on the electrical transport properties is probably related to the formation of short conduction channels at the semiconductors interface, which may exhibit two-dimensional electron gas (2DEG) behavior. © 2012 Elsevier B.V. All rights reserved.

Coupling Surface-Enhanced Resonance Raman Scattering and Electronic Tongue as Characterization Tools to Investigate Biological Membrane Mimetic Systems

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Nanostructured hybrid films containing nanophosphor: Fabrication and electronic spectral properties

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structural and Electronic Effects of Incorporating Mn in TiO2 Films Grown by Sputtering: Anatase versus Rutile

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Periodic study on the structural and electronic properties of bulk, oxidized and reduced SnO2(110) surfaces and the interaction with O-2

The structural and electronic properties of bulk and both oxidized and reduced SnO2(110) surfaces as well as the adsorption process of O-2 on the reduced surface have been investigated by periodic DFT calculations at B3LYP level. The lattice parameters, charge distribution, density of states and band structure are reported for the bulk and surfaces. Surface relaxation effects have been explicitly taken into account by optimizing slab models of nine and seven atomic layers representing the oxidized and reduced surfaces, respectively. The conductivity behavior of the reduced SnO2(110) surface is explained by a distribution of the electrons in the electronic states in the band gap induced by oxygen vacancies. Three types of adsorption approaches of O-2 on the four-fold tin at the reduced SuO(2)(110) surface have been considered. The most exothermic channel corresponds to the adsorption of O-2 parallel to the surface and to the four-fold tin row, and it is believed to be associated with the formation of a peroxo O-2(2-) species. The chemisorption of O-2 on reduced SnO2(110) surface causes a significant depopulation of states along the band gap and it is shown to trap the electrons in the chemisorbed complex producing an electron-depleted space-charge layer in the inner surface region of the material in agreement with some experimental evidences. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Thermodynamic and electronic study of Ga-1 _ xMnxN films. A theoretical study

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Surface structure and electronic properties of Pt-Fe/C nanocatalysts and their relation with catalytic activity for oxygen reduction

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

On the photoluminescence behavior of samarium-doped strontium titanate nanostructures under UV light. A structural and electronic understanding

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Relation between antioxidant activity and electronic structure of Phenols

We describe a new physicochemical descriptor of the antioxidant activity of phenols, the energy difference between the two highest occupied molecular orbitals, which we believe will improve quantitative structure-activity relationship studies about these compounds. (C) 2003 Wiley Periodicals, Inc.

Composition and electronic structure of Zn7-xMxSb2O12 (M = Ni and Co) spinel compounds

The relation between the composition and electronic structure of the perfectly inverse spinel compound Zn7-xMxSb2O12 (M = Ni and Co) has been studied by powder X-ray diffraction and X-ray photoelectron spectroscopy. Changes in the site occupancy are associated with shifts in the core levels as observed in the core level spectral analyses. The configuration of the density of states in the valence band due to the Co and Ni states can be observed in the valence band spectra. (C) 2004 Elsevier B.V. All rights reserved.

Structural and electronic properties of PbTiO3 slabs: a DFT periodic study

Structural and electronic properties of the bulk and relaxed surfaces (TiO2 and PbO terminated) of cubic PbTiO3 are investigated by means of periodic quantum-mechanical calculations based on density functional theory. It is observed that the difference in surface energies is small and relaxations effects are most prominent for Ti and Ph surface atoms. The electronic structure shows a splitting of the lowest conduction bands for the TiO2 terminated surface and of the highest valence bands for the PbO terminated slab. The calculated indirect band gap is: 3.18, 2.99 and 3.03 eV for bulk, TiO2 and PbO terminations, respectively. The electron density maps show that the Ti-O bond has a partial covalent character, whereas the Pb-O bonds present a very low covalency. (C) 2004 Elsevier B.V. All rights reserved.

Density functional theory study on the structural and electronic properties of low index rutile surfaces for TiO2/SnO2/TiO2 and SnO2/TiO2/SnO2 composite systems

The present study is concerned with the structural and electronic properties of the TiO2/SnO2/TiO2 and SnO2/TiO2/SnO2 composite systems. Periodic quantum mechanical method with density functional theory at the B3LYP level has been carried out. Relaxed surface energies, structural characteristics and electronic properties of the (I 10), (0 10), (10 1) and (00) low-index rutile surfaces for TiO2/SnO2/TiO2 and SnO2/TiO2/SnO2 models are studied. For, comparison purposes, the bare rutile TiO2 and SnO2 structures are also analyzed and compared with previous theoretical and experimental data. The calculated surface energy for both rutile TiO2 and SnO2 surfaces follows the sequence (110) < (010) < (101) < (001) and the energy increases as (010) < (101) < (110) < (001) and (010) approximate to (110) < (101) < (001) for SnO2/TiO2/SnO2 and TiO2/SnO2/TiO2 composite systems, respectively. SnO2/TiO2/SnO2 presents larger values of surface energy than the individual SnO2 and TiO2 metal oxides and the TiO2/SnO2/TiO2 system renders surface energy values of the same order that the TiO2 and lower than the SnO2. An analysis of the electronic structure of the TiO2/SnO2/TiO2 and SnO2/TiO2/SnO2 systems shows that the main characteristics of the upper part of the valence bands for all the studied surfaces are dominated by the external layers, i.e., by the TiO2 and the SnO2, respectively, and the topology of the lower part of the conduction bands looks like the core layers. There is an energy stabilization of both valence band top and conduction band bottom for (110) and (010) surfaces of the SnO2/TiO2/SnO2 composite system in relation to their core TiO2, whereas an opposite trend is found for the same surfaces of the TiO2/SnO2/TiO2 composite system in relation to the bare SnO2. The present theoretical results may explain the growth of TiO2@SnO2 bimorph composite nanotape.

Structural and Electronic Properties of Lithiated SnO2. A Periodic DFT Study

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Synthesis, structure, and electronic and EPR spectra of copper(II) complexes containing the [CuBr4]2- anion and triphenylarsine oxide

The preparation and characterization of (Ph3AsOH)2[CuBr4] and [Cu(Ph3AsO)4][CuBr4] are reported (Ph3AsO = triphenylarsine oxide). Crystallographic analysis of the monoclinic crystals of (Ph3AsOH)2[CuBr4] (space group C2/c, a = 17.569 (3) Å, b = 13.090 (2) Å, c = 16.933 (2) Å, and β = 105.64 (2)°, R = 0.055 and Rw = 0.057) revealed the presence of compressed [CuBr4]2- tetrahedra of C2 symmetry with Cu-Br distances of 2.340 (1) and 2.437 (1) Å and trans-Br-Cu-Br angles of 139.2 (1) and 122.4 (1)°. The oxonium cations hydrogen bond to the bromine atoms involved in the longer Cu-Br bonds and the smaller trans-Br-Cu-Br angle. Single-crystal electronic and EPR spectra are interpreted in terms of the observed [CuBr4]2- geometry. Analysis of the electronic and EPR spectra of [Cu(Ph3AsO)4][CuBr4] led to the postulation of the presence of planar [Cu(Ph3AsO)4]2+ cations and distorted tetrahedral [CuBr4]2- anions. © 1992 American Chemical Society.

Crystal, Molecular, and Electronic Structure of 1-Acetyl-indoline and Derivatives

The crystal and molecular structures of the following molecules have been determined: 1-acetyl-indoline, 1-acetyl-5-nitro-indoline, 1-acetyl-5-nitro-7-bromo-indoline, 1-acetyl-5-bromo-7-nitro-indoline, and 1-acetyl-5-bromo-7-nitro-indol. Molecular orbital calculations are performed for these compounds and two related species.