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Temperature dependent electron transport properties of individual ZnO mirco/nanowires from 293 K to 473 K were investigated by a four-probe method, and the size dependence of activation energy was studied. The conductivity increased with the increasing temperature, which was attributed to the thermal activations of donors: shallow donors and deep donors. The activation energy related to shallow donors was effectively independent of the radius, suggesting that it was associated with the surface conduction channel of ZnO wire, while a nearly inverse dependence of the activation energy of deep donors on the wire diameter may result from the dielectric confinement effect. [ABSTRACT FROM AUTHOR]

The electric-induced nanodamage in single ZnO nanowires was measured with a conductive atomic force microscope. The damage threshold voltage was estimated to be 7.0±0.5 V for the 5 nm nanowires. The thickness along a single nanowire during the damaging process can be accurately modulated by controlling the evaporation time and applied voltage in selected areas. The transverse conductance was found to increase as the heights of the single damaging nanowire increased, which is suggested to be attributed to the quantum confinement effect. [ABSTRACT FROM AUTHOR]

Abstract: Negative differential resistance was observed in current–voltage curves of ZnO nanowire embedded sensors in the ethanol environment and conductances at critical points are inversely proportional to the concentration, while this phenomenon was not observed in the toluol environment. Through individual ZnO nanowire experiments, we attribute negative differential resistance to the joint effect of electron transference in the oxidation process of hydroxyls and the nonequilibrium occupation factor for electrons in the process saturating with generation rate of carriers at the ZnO nanowire surface. The inverse variation is associated with the densities of donor and acceptor traps. These results indicate that surface depletion can be beneficial to nanodevices. [Copyright &y& Elsevier]

Abstract: Modulation of electron injection over Schottky barrier was realized by employing electron beam irradiation on the metal/ZnO-nanowire contact. The structure revealed a good response to the illumination at a scanning frequency of 0.1 Hz, which can be enhanced by increasing bias and decreased with the increase of electron beam energy. These phenomena can be attributed to the Schottky barrier formed at the metal/ZnO-nanowire interface which limits the electron transport across the contact. The electron beam irradiation gives rise to high efficiency of electron injection over the barrier, while the interplay between charge discreteness, coherent scattering, and Coulomb interaction may reduce the conductivity. [Copyright &y& Elsevier]

We report a room temperature negative differential resistance (RT-NDR) phenomenon in the ZnO nanowire/CuPc nanofilm hybrid heterojunction by using conductive atomic force microscope (C-AFM). The NDR behavior is observed only in the positive sample bias range with the peak-to-valley current ratio as high as 4.7 in the dark. Under light illumination (centered at 716 nm), the NDR peak current increases from 2.1 to 7.53 nA and the peak voltage decreases from 4.2 to 3.1 V with increasing the light intensity. The origin and the modulation of the NDR are discussed in terms of energy band diagram of the heterojunction. [ABSTRACT FROM AUTHOR]

The localized ultraviolet photoresponse in single bent ZnO micro/nanowires bridging two Ohmic contacts has been investigated. The ZnO micro/nanowire has a higher photoresponse sensitivity of about 190% at the bent region (bending strain: about 4%) than that at the straight region (about 50%). The rise and decay time constants are almost the same in the straight and bent regions of the ZnO micro/nanowire. A possible mechanism has been proposed and discussed. The bent ZnO micro/nanowires could be potentially useful for fabricating the coupled piezoelectric and optoelectronic nanodevices. [ABSTRACT FROM AUTHOR]

Zn1-xMnxO nanowires were synthesized through chemical vapor deposition of pure Zn and MnCI2 power mixtures on silicon substrates. The morphology, structure and composition were measured by SEM, TEM, EDX and XRD. Magnetic proper- ties were measured by SQUID. The results show that the nanowires exhibit clear ferromagnetic behavior at low temperature. An abnormal peak is observed in the M-T curve at 55 K in a magnetic field of 500 Oe. [ABSTRACT FROM AUTHOR]

Well-aligned ZnO nanowires were synthesized by simple physical vapor deposition using c-oriented ZnO thin films as substrates without catalysts or additives. The synthesized ZnO nanowires have two typical average diameters: 60 nm in majority and 120 nm in minority. They are about 4 μm in length and well aligned along the normal direction of the substrate. Most of the synthesized ZnO nanowires are single crystalline in a hexagonal structure and grow along the [001] direction. The c-oriented ZnO thin films control the growth direction. Photoluminescence spectrum was measured showing a single strong ultraviolet emission (380 nm). Such result indicates that the ZnO nanowire arrays can be applied to excellent optoelectronic devices. [ABSTRACT FROM AUTHOR]

We report electrically driven ultraviolet lasing by electrical injection in a single ZnO micro/nanowire. Heterojunctions were fabricated by contacting poly(3,4-ethylenedioxythiophene): poly(styrenexulfonate) (PEDOT:PSS) with one end of a single ZnO wire. At an excitation injection of ∼1 A/cm2, the electroluminescence spectrum showed a near-ultraviolet lasing action. This phenomenon was understood based on whispering-gallery mode, which results from trajectories that traverse a polygonal cross-section near the edges of the cylinder. The reduction of some modes was associated with the surface states or defects and the resonance below the intrinsic exciton emission of ZnO is related to electron accumulation at the polymer/ZnO interface. [ABSTRACT FROM AUTHOR]

Scanning conductance microscopy (SCM) is used to measure the dielectric constant of a single pencil-like zinc oxide (ZnO) nanowire with the diameters ranging from 85 to 285 nm. As the diameter decreases, the dielectric constant of ZnO nanowire is found to decrease from 6.4 to 2.7, which is much smaller than that of the bulk ZnO of 8.66. A core–shell composite nanowire model in terms of the surface dielectric weakening effect is proposed to explore the origin of the size dependence of dielectric constant, and the experimental results are well explained. [ABSTRACT FROM AUTHOR]