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Abstract: Zinc oxide (ZnO) quantum dots (QDs) were fabricated on silicon substrates by metal organic chemical vapor deposition. Formation of QDs is due to the vigorous reaction of the precursors when a large amount of precursors was introduced during the growth. The size of the QDs ranged from 3 to 12nm, which was estimated by high-resolution transmission electron microscopy. The photoluminescence measured at 80K showed that the emission of QDs embedded film ranged from 3.0 to 3.6eV. The broad near-band-edge emission was due to the quantum confinement effect of the QDs. [Copyright &y& Elsevier]

Abstract: Zinc oxide nanowhiskers with multipod structures have been fabricated on copper-coated Si wafer by sintering the mixture of ZnO and graphite powders in air. The multipod nanowhisker shows tetrapod, tripod and hexapod morphologies with legs of 100–500nm in diameter and several microns in length. The legs of the multipod nanowhisker intercross at a central knot of the whisker. The octahedron twin nucleus is responsible for the tetrapod structure and possibly responsible for the tripod structure as well. The hexapod structure is due to a stacked nucleus of two octahedron nuclei. [Copyright &y& Elsevier]

Abstract: Based on a vapor-phase transport process, self-organized nanocomb structures of ZnO were fabricated on Au-coated Si substrate by employing a mixture of ZnO and graphite powders as source materials. The morphology of the product showed a ribbon-like stem and nanorod array aligned evenly along one side of the nanoribbon. It was found that the nanoribbon grew mainly along direction and the self-assembled branching nanorods grew epitaxially along [0001] orientation from the (0002) plane of the stem. The growth process was analyzed in detail. [Copyright &y& Elsevier]

Abstract: A focus-switchable liquid crystal (LC) lens made of polymer–LC composite was fabricated by a molding technique. The focus-switchable LC lens fabricated had a diameter of 6.0mm and center thickness of 67μm. The focal length obtained was about 48cm. The lens showed good optical properties and strong polarization dependence. Its focus can be switched either by applying a low driving voltage (about 3V) or by changing the polarization of the incident light. Such focus-switchable polymer–LC lens fabricated by this kind of technique is potentially useful in many optical systems, such as optical tweezers, machine vision, eye glasses. [Copyright &y& Elsevier]

Abstract: It is known in tris-(8-hydroxyqunoline) aluminum-based organic light-emitting device, that copper-phthalocyanines (CuPc) inserted between the anode and the hole transport layer (HTL), has two opposing roles: improving and reducing the current injection. Despite of its controversy, no work has been done to clear the matter. Here, we addressed this controversy with experiments and simulations. Our results showed that, CuPc inserted between indium-tin-oxide (ITO) and HTL, played dual roles of hole-blocking and hole-injection. CuPc layer improves holes injection, when the amount of oxygen at the CuPc/HTL interface is small. However, CuPc layer switches to impede holes injection, when the oxygen diffusion from ITO to CuPc/HTL interface is severe. [Copyright &y& Elsevier]

Abstract: The structural, optical and electrical properties of polycrystalline ZnO thin films deposited by metal organic chemical vapor deposition are studied. The surface roughness of the as-deposited ZnO thin films reduces with the increase of growth temperature from 200 to 400°C, and increases with further increase of the growth temperature from 400 and 500°C. All the films possess a transmittance near 100% in the visible region except the samples grown at temperatures of 450 and 500°C. The resistivity of ZnO thin films decreases with the increase of growth temperature. The optical band gap energy of the as-grown ZnO blue-shifted from 3.295 to 3.447eV as the growth temperature decreased from 500 to 200°C, which is due to the increase of localized states in the conduction band, associated with the amorphitization of the film. [Copyright &y& Elsevier]

Wurtzite ZnO thin films with different epitaxial relationships have been grown on (0 0 1)-, (0 1 1)-, and (1 1 1)LaAlO 3 (LAO) single-crystal substrates by pulsed laser deposition. Nonpolar (1 1 2 ¯ 0)ZnO films with two orthogonal domains were obtained on (0 0 1) LAO, in which the in-plane orientation relationship is demonstrated to be 〈0 0 0 1〉 ZnO //〈1 1 0〉 LAO . For ZnO on (0 1 1)- and (1 1 1)LAO substrates, a single-domain epitaxy with c axial orientation is observed, in which the in-plane relationships were 〈1 1 ¯ 0 0〉 ZnO //〈0 1 1 ¯ 〉 LAO irrespective of the substrate orientations. Based on the in-plane orientation relationship, the lattice mismatch has been obtained for these three oriented ZnO/LAO heterointerfaces. [ABSTRACT FROM AUTHOR]

Abstract: In this letter, we report on the realization of the p-type ZnO film by in situ nitrogen doping and subsequent thermal activation, as well as the discussions on the doping mechanism. Through the high temperature activation, a conversion of conductivity from n- to p-type with a hole concentration of ∼1019/cm3 has been observed by Hall measurements, accompanied with the formation and dissociation of N–H complex investigated by Raman spectra. These observations provide probability on the passivation effect of N–H complex and dehydrogenation process at high temperature, as confirmed by the variation of N and H atomic concentration in the secondary ion mass spectra. The dehydrogenation process in oxygen ambient at 900°C led to the dissociation of NO–H complexes, resulting in the formation of isolated NO acceptors and compensation to the intrinsic donor-like defects. The N-related acceptor bound exciton in photoluminescence with a small binding energy of 100meV and high p-type conductivity in activated ZnO:N film imply the important role of dehydrogenation effect to the realization of p-type ZnO. [Copyright &y& Elsevier]

Abstract: We investigated the optical and transport properties of charge carriers in doped amorphous Tris (8-hydroxyquinolinato) aluminum (Alq3) films from room temperature to 130°C. The doping concentration of dopant DCM was up to 24wt% in Alq3 films. The current–voltage, electroluminescence (EL) and light–current characteristics were measured. The current density was sharply increased up to a DCM concentration of 1.5wt% in Alq3 films for the same bias voltage. The EL peak position shifted from green to red color with DCM doping concentration in Alq3. The highest EL efficiency was found for a DCM doping concentration of 0.5wt%. The EL intensity was increased by about 2.5 times than that of the pure Alq3. The EL intensity was reduced with temperature. [Copyright &y& Elsevier]

Abstract: The band structures of wurtzite ZnO are calculated using the empirical pseudopotential method (EPM). The 8 parameters of the Zn and O atom pesudopotential form factors with Schluter''s formula are obtained. The effective mass parameters are extracted by using k.p Hamiltonian to fit the EPM results. The calculated band edge energies (E g, E A, E B, and E C) at Γ point are in good agreement with experimental results. The ordering of ZnO at the top of valence band is found to be A(Γ7)–B(Γ9)–C(Γ7) due to a negative spin–orbit (SO) splitting. Based on the band parameters obtained, the valence hole subbands of wurzite ZnO/Mg x Zn1− x O tensile-strained quantum wells (QWs) with different well widths and Mg compositions are calculated using 6-band k.p method. [Copyright &y& Elsevier]