Photovoltaic device on a single ZnO nanowire p-n homojunction

A photovoltaic device was successfully grown solely based on the single ZnO p-n homojunction nanowire. The ZnO nanowire p-n diode consists of an as-grown n-type segment and an in situ arsenic-doped p-type segment. This p-n homojunction acts as a good photovoltaic cell, producing a photocurrent almost 45 times larger than the dark current under reverse-biased conditions. Our results demonstrate that the present ZnO p-n homojunction nanowire can be used as a self-powered ultraviolet photodetector as well as a photovoltaic cell, which can also be used as an ultralow electrical power source for nanoscale electronic, optoelectronic and medical devices.     

Sensitivity of a superconducting nanowire detector for single ions at low energy

We report on the characterization of a superconducting nanowire detector for ions at low kinetic energies. We measure the absolute single-particle detection efficiency η and trace its increase with energy up to η = 100%. We discuss the influence of noble gas adsorbates on the cryogenic surface and analyze their relevance for the detection of slow massive particles. We apply a recent model for the hot-spot formation to the incidence of atomic ions at energies between 0.2 and 1 keV. We suggest how the differences observed for photons and atoms or molecules can be related to the surface condition of the detector and we propose that the restoration of proper surface conditions may open a new avenue for SSPD-based optical spectroscopy on molecules and nanoparticles.     

Optical switches based on CdS single nanowire

CdS nanowires have been synthesized by a composite-hydroxide-mediated approach. The characterization of the nanowire with X-ray diffraction, scanning electron microscopy, and transmission electron microscopy indicated a single-crystalline hexagonal structure growing along direction with length up to 100 μm. The UV-visible reflection spectrum demonstrated a band gap of 2.36 eV. A strong light emission centered at 543 nm was observed under different excitation wavelengths of 300, 320, 360 and 400 nm, which was further confirmed by a bright fluorescent imaging of a single CdS nanowire. The photocurrent response based on a single CdS nanowire showed distinct optical switch under the intermittent illumination of white light. The rise and decay time were less than 1.0 and 0.2 s, respectively, indicating high crystallization with fewer trap centers in the CdS nanowires. It is possible that the undesirable trapping effects on grain-boundaries for photoconductors could be avoided thanks to the single-crystalline nature of the CdS nanowires.     

Novel nonvolatile memory with multibit storage based on a ZnO nanowire transistor

We demonstrate a room temperature processed ferroelectric (FE) nonvolatile memory based on a ZnO nanowire (NW) FET where the NW channel is coated with FE nanoparticles. A single device exhibits excellent memory characteristics with the large modulation in channel conductance between ON and OFF states exceeding 10(4), a long retention time of over 4 × 10(4) s, and multibit memory storage ability. Our findings provide a viable way to create new functional high-density nonvolatile memory devices compatible with simple processing techniques at low temperature for flexible devices made on plastic substrates.     

Current rectification in a single silicon nanowire p-n junction

Diodes within individual silicon nanowires were fabricated by doping them during growth to produce p-n junctions. Electron beam lithography was then employed to contact p- and n-doped ends of these nanowires. The current-voltage (I-V) measurements showed diode-like characteristics with a typical threshold voltage (Vt) of about 1 V and an ideality factor (n) of about 3.6 in the quasi-neutral region. The reverse bias I-V measurement showed an exponential behavior, indicating tunneling as the current leakage mechanism.     

Ultraviolet photoconductance of a single hexagonal WO3 nanowire

The ultraviolet (UV) photoconductance properties of a single hexagonal WO₃ nanowire have been studied systematically. The conductance of WO₃ nanowires is very sensitive to ultraviolet B light and a field-effect transistor (FET) nanodevice incorporating a single WO₃ nanowire exhibits excellent sensitivity, reversibility, and wavelength selectivity. A high photoconductivity gain suggests that WO₃ nanowires can be used as the sensing element for UV photodetectors. Measurements under UV light in vacuum show that the adsorption and desorption of oxygen molecules on the surface of the WO₃ nanowire can significantly influence its photoelectrical properties. The WO₃ nanowires have potential applications in biological sensors, optoelectronic devices, optical memory, and other areas.      

Direct quantification of gold along a single Si nanowire

The presence of gold on the sidewall of a tapered, single silicon nanowire is directly quantified from core-level nanospectra using energy-filtered photoelectron emission microscopy. The uniform island-type partial coverage of gold determined as 0.42+/-0.06 (approximately 1.8 ML) is in quantitative agreement with the diameter reduction of the gold catalyst observed by scanning electron microscopy and is confirmed by a splitting of the photothresholds collected from the sidewall, from which characteristic local work functions are extracted using a model of the full secondary electron distributions.     

Vertical single nanowire devices based on conducting polymers

A simple scheme for single conducting polymer nanowire fabrication and device integration is presented. We discuss a combined top-down and bottom-up approach for the sequential, precise manufacture of vertical polyaniline nanowires. The method is scalable and can be applied on rigid as well as on flexible substrates. The kinetics of the template-confined growth is presented and discussed. We further study the electrical behavior of single vertical polyaniline nanowires and address the fabrication of crossbar latches using a criss-cross arrangement of electrodes. The as-synthesized polyaniline nanowires display electric conductivities reaching values as high as 0.4 S cm?1.     

Carrier depletion and exciton diffusion in a single ZnO nanowire

Carrier depletion and transport in a single ZnO nanowire Schottky device have been investigated at 5?K, using cathodoluminescence measurements. An exciton diffusion length of 200?nm has been determined along the nanowire axis. The depletion width is found to increase linearly with the reverse bias. The origin of this unusual dependence in semiconductor material is discussed in terms of charge location and dimensional effects on the screening of the junction electric field.     

Coupled electrooxidation and electrical conduction in a single gold nanowire

The resistance, R, of single gold nanowires was measured in situ during electrooxidation in aqueous 0.10 M sulfuric acid. Electrooxidation caused the formation of a gold oxide that is approximately 0.8 monolayers (ML) in thickness at +1.1 V vs saturated mercurous sulfate reference electrode (MSE) based upon coulometry and ex situ X-ray photoelectron spectroscopic analysis. As the gold nanowires were electrooxidized, R increased by an amount that depended on the wire thickness, ranging from Delta R/ R 0.10V = 14% for a 63 nm (h) x 200 nm (w) wire to 57% for an 18 nm (h) x 95 nm (w) wire at +1.1 V. These nanowires were millimeters in total length, but just 46 mum lengths were exposed to the electrolyte solution. The oxidation process and the accompanying increase in R were reversible: Reduction of the oxide at +0.10 V resulted in recovery of the reduced wire R except for a small resistance offset caused by the dissolution of approximately 0.4 ML of gold during each oxidation/reduction cycle. The measured increase in R during oxidation exceeds by a factor of 4 the predicted increases in R associated with the reduction in cross-sectional area of the nanowire and the expected decrease in the specular scattering parameter, p, at the gold-oxide interface at wire surfaces. We propose that this anomalous increase in R is caused by infiltration of the oxide into the nanowire at grain boundaries.     

Polarization-dependent surface-enhanced Raman scattering from a silver-nanoparticle-decorated single silver nanowire

Single silver nanowires produced by DC electrodeposition in porous anodic alumina templates were surface-functionalized with the bifunctional molecule 4-aminobenzenthiol (ABT) then exposed to aqueous silver nanoparticles resulting in a silver nanoparticle-decorated silver nanowire. The polarization dependent surface-enhanced Raman (SERS) signal from this system showed significant intensity anisotropy when measured at a midsection of the nanowire, where the largest SERS intensities were observed when the incident light was polarized perpendicular to the nanowire's long axis but was almost isotropic near the tip of the nanowire. The observed effects were accounted for in terms of the electromagnetic fields concentrated in the collection of hot spots created through the ABT-linker-driven nanoparticle-nanowire self-assembly process.     

Piezoelectric field effect transistor and nanoforce sensor based on a single ZnO nanowire

Utilizing the coupled piezoelectric and semiconducting dual properties of ZnO, we demonstrate a piezoelectric field effect transistor (PE-FET) that is composed of a ZnO nanowire (NW) (or nanobelt) bridging across two Ohmic contacts, in which the source to drain current is controlled by the bending of the NW. A possible mechanism for the PE-FET is suggested to be associated with the carrier trapping effect and the creation of a charge depletion zone under elastic deformatioin. This PE-FET has been applied as a force/pressure sensor for measuring forces in the nanonewton range and even smaller with the use of smaller NWs. An almost linear relationship between the bending force and the conductance was found at small bending regions, demonstrating the principle of nanowire-based nanoforce and nanopressure sensors.     

High mass loading Ni4Coi-OH@CuO core-shell nanowire arrays obtained by electrochemical reconstruction for alkaline energy storage

The design of three-dimensional(3D)core-shell heterostructures is an efficient method to achieve high mass specific capacity of electroactive materials under hi...     

Efficient electric-discharge CO2 laser with a prepulse formed by a generator with an inductive energy storage device

Results are presented of experimental investigations of a CO₂ laser pumped by a self-sustained discharge from a generator with an inductive energy storage device and a semiconductor current chopper. It is shown that the energy stored in the inductance of the discharge circuit can form a prepulse capable of depositing most of the energy in the active mixture for nearoptimum values of the parameter E/p. A radiation energy of 3 J was achieved in an electricdischarge laser with a 0.181 liter active volume with a 17% efficiency relative to the energy stored in the capacitive storage device. Pis’ma Zh. Tekh. Fiz. 24, 57–61 (February 26, 1998)     

单根CuTCNQ纳米线的电学开关特性

用溶液法制备了CuTCNQ纳米线。用X射线衍射(XRD)和扫描电子显微镜(SEM)表征了样品的结构及形貌,用拉曼光谱(Raman)研究了CuTC-NQ纳米线的电荷转移情况。研究了其不同温度下的电学特性。CuTCNQ纳米线的长度为1～8μm,直径50～300nm。XRD结果显示制备得到的CuTCNQ为Ⅰ相。研究表明,在外加电场作用下,单根CuTCNQ纳米线表现出可逆的电开关特性,阻态转变前后其电阻的变化达3个数量级。高低阻态转变电场阈值约为1.8V/μm。另外,CuTCNQ纳米线的电阻随着温度的降低而增大,当温度低于临界值160K时,低阻态的CuTCNQ纳米线将出现负阻效应。     

Direct observation of field emission in a single TaSi2 nanowire

The electric potential change in a single TaSi2 nanowire during field emission was visualized by means of electron holography. During the field emission, the interference fringes of the electron hologram were blurred locally between the TaSi2 nanowire and anode. This phenomenon was interpreted as being due to a change in the electric potential of approximately 1 V in the TaSi2 nanowire after each ballistic emission. The experiments on the single TaSi2 nanowire field emission behavior provide the useful information for understanding the field emission in the nano-field-emitting device.     

Anisotropic third-order optical nonlinearity of a single ZnO micro/nanowire

We report a systematic study about the anisotropic third-order optical nonlinearity of a single ZnO micro/nanowire by using the Z-scan method with a femtosecond laser. The two-photon absorption coefficient and nonlinear refraction index, which are measured as a function of polarization angle and sample orientation angle, exhibit oscillation curves with a period of π/2, indicating a highly polarized optical nonlinearity of the ZnO micro/nanowire. Further studies show that the polarized optical nonlinearity of the ZnO micro/nanowire is highly size-dependent. The results indicate that ZnO nanowire has great potential in applications of nanolasers, all-optical switching and polarization-sensitive photodetectors.     

Size dependence of dielectric constant in a single pencil-like ZnO nanowire

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.     

Laser detection of electrical service safety in a single ZnO nanowire

The electrically induced quenching of the photoluminescence (PL) intensity and fracture in a single ZnO nanowire were investigated. As the applied voltage increases, the quenching of PL intensity and the red-shift of ultraviolet (UV) emission peak were clearly observed, which are explained by the current-induced Joule heating in the ZnO nanowire. By using this mechanism, the UV laser was successfully used to monitor the safe current density and identify the current-induced fracture in a single ZnO nanowire.