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Mapping individual radiative recombination channels at the nanoscale in direct correlation with the underlying crystal structure and composition of III–V semiconductor nanostructures requires unprecedented highly spatially resolved spectroscopy methods. Here, we report on a direct one-by-one correlation between the complex radial structure and the distinct carrier recombination channels of single GaAs-AlGaAs core-multishell nanowire heterostructures using low temperature cathodoluminescence spectroscopy directly performed in a scanning transmission electron microscope. Based on an optimized focused ion beam fabrication of the optically active specimen, we directly visualize the radial luminescence evolution and identify four distinct emission lines, i.e., the near band edge and defect luminescence of the GaAs core (819 nm, 837 nm), the emission of the single embedded GaAs quantum well (QW, 785 nm), and the AlGaAs shell luminescence correlated with alloy fluctuations (650–674 nm). The detailed radial luminescence profiles are anticorrelated between QW luminescence and core emission, illustrating the radial carrier transport of the core-shell system. We inspected in detail the low-temperature capture of excess carriers in the quantum well and barriers. [ABSTRACT FROM AUTHOR]

The electrical properties of individual NiFe/Pt multilayer nanowires have been measured in situ by nanomanipulators in a scanning electron microscope. The electrical measurement of ∼50 nm diameter individual NiFe/Pt multilayer nanowires with polycrystalline microstructure shows that the nanowires have a resistivity of ∼2.2 × 10-7 Ω m (corresponding to a conductivity of ∼4.5× 106 Ω-1 m-1) and average resistance of individual NiFe-Pt interfaces of ∼0.2 Ω. The maximum failure current density of an individual NiFe/Pt nanowire was measured to be ∼9.63 × 1011 A m-2. [ABSTRACT FROM AUTHOR]

The influence of external magnetic fields on the bending vibration of a one-side clamped iron filled carbon nanotube (CNT) has been analyzed theoretically and experimentally, with particular consideration given to the changes in the resonance frequency. The model involves the application of a modified Euler-Bernoulli-beam to analyze the zero field oscillatory behavior, as well as a magnetostatic approach used to determine the influence of any external field distributions. The experiments were conducted in situ in a scanning electron microscope. The measured magnetic moment of the nanowire at room temperature was μ = 2.1 × 10-14 Am2. Due to the favorable geometry of the CNT oscillator, the raw signal obtained using this approach is significantly more favorable than that with state of the art cantilever magnetometry. The obtained good agreement between model and experiment provides a valuable basis for the development of nanoelectromechanical systems in which magnetic interactions are relevant. [ABSTRACT FROM AUTHOR]

In situ uniform growth of ZnO nanowires was realized and monitored at real time by heating zinc film in an environmental scanning electron microscope. Better controllability and repeatability were obtained by using zinc film as source material compared to traditionally used zinc powder. Morphology of the as-grown ZnO nanowires was found to depend on both the growth temperature and holding time. Low temperature (500 °C) and short growth time (∼20 min) favor one-dimensional nanowire growth, whereas longer holding time (>40 min) or higher temperature (700 °C) lead to nanosheet growth. The results suggest that the zinc vapor partial pressure is vital in determining the final morphology. These results help to give more insights into the mechanism of ZnO nanowire synthesis. [ABSTRACT FROM AUTHOR]

The electrical transport properties and breakdown behaviors of single n-i-n-n+ GaN nanowires (NWs) are investigated through in-situ nanoprobing inside a scanning electron microscope (SEM). The nanoprobing contact resistance is dramatically reduced by increasing the Si-doping concentration of the top n+-GaN segment of the NW. The dependence of the NW breakdown parameters (i.e., breakdown voltage, power, and current density) on the n+-GaN Si-doping concentration and the NW diameter is experimentally quantified and explained by the localized thermal decomposition mechanism of the NW. Enabled by the low NW-nanoprobe contact resistance, a breakdown current density of 4.65 MA/cm2 and a breakdown power of 96.84 mW are achieved, both the highest among the previously reported results measured on GaN NWs. [ABSTRACT FROM AUTHOR]

As far as we know, all the single nanowire (NW) metal-semiconductor field-effect transistors (MESFETs) reported are based on n-type NWs. We report MESFETs based on p-type Zn3P2 single NWs in this paper. The p-type Zn3P2 single NW MESFETs operate in the enhancement mode (E-mode). The source-drain current decreases with gate bias (VG) increasing, confirming the p-type conductance of the Zn3P2 NWs. Typically, the p-type Zn3P2 single NW MESFET has an on/off current ratio of 103, a threshold gate voltage of -0.4 V, and a maximum transconductance of 110 nS. [ABSTRACT FROM AUTHOR]

Mechanical properties of individual InAs nanowires (NWs) synthesized by metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) methods are studied by in-situ tensile tests in a scanning electron microscope and their fracture strength and Young's modulus are obtained. The two types of NWs both exhibit brittle fracture with a maximum elastic strain up to ~10%. Their fracture strength distributes in a similar range of ~2-5GPa with a general trend of increasing with NW volume decrease, which is well described by Weibull statistic with a smaller Weibull modulus and a higher characteristic strength for MOCVD NWs. Young's modulus is determined to be 16-78GPa with an average value of 45 GPa and no dependence on NW diameter for MOCVD NWs and 34-79GPa with an average value of 58GPa for MBE NWs. [ABSTRACT FROM AUTHOR]

Optimum design of efficient nanowire solar cells requires better understanding of light diffusion in a nanowire array. Here we demonstrate that our recently developed ultrafast all-optical shutter can be used to directly measure the dwell time of light in a nanowire array. Our measurements on disordered ZnO nanowire arrays, 'nanowire forests,' indicate that the photon mean free path and the dwell time of light can be well predicted from SEM images. [ABSTRACT FROM AUTHOR]

We present a simple fabrication technique for lateral nanowire wrap-gate devices with high capacitive coupling and field-effect mobility. Our process uses e-beam lithography with a single resist-spinning step and does not require chemical etching. We measure, in the temperature range 1.5-250 K, a subthreshold slope of 5-54 mV/decade and mobility of 2800-2500 cm2/Vs-significantly larger than previously reported lateral wrap-gate devices. At depletion, the barrier height due to the gated region is proportional to applied wrap-gate voltage. [ABSTRACT FROM AUTHOR]

This note presents two experimental techniques for mechanical and electrical characterization of individual nanowires inside a scanning electron microscope (SEM). Tensile testing is realized by transferring a nanowire to a microelectromechanical systems device that stretches the nanowire and measures the elongations and tensile forces. The device consists of an electrostatic actuator and two capacitive sensors, capable of acquiring all measurement data (force and displacement) electronically without relying on electron microscopy imaging. For electrical characterization, four-point probe measurement of individual nanowires is performed automatically by controlling four nanomanipulators with SEM visual feedback. A feedforward controller is incorporated into the control system to improve the response time. This work represents advances in nanomaterial testing and automated nanomanipulation. [ABSTRACT FROM AUTHOR]

We investigated the stability of ZnO nanowires in a metal-semiconductor-metal structure by applying a longitudinal electric field inside a scanning electron microscope equipped with manipulators. The electrical transport was well simulated by the thermionic-field-emission model and the failure of single crystalline ZnO nanowires was directly observed when the applied electric field reached the break point, an electric field intensity of ∼106 V/m. The recrystallization of ZnO nanowires from single crystalline to polycrystalline pearl-like structure in the failure process was also investigated. Experimental results indicated that the failure is attributed to a joint effect of high electric field and Joule heating. [ABSTRACT FROM AUTHOR]

This work presents an accurate measurement of electrical properties of individual gold nanowires, directly measured by nanomanipulators in situ in a scanning electron microscope. The electrical testing of 55 nm width gold nanowires, with a bamboo-type polycrystalline micorstructure, shows that individual gold nanowires have an ideal resistivity of about 2.26 μΩ cm and remarkably high failure current density of 4.94×108 A cm-2. The measurement of resistance (R) versus nanowire length of individual nanowires shows that the intrinsic conductivity of the gold nanowire is 4.45×107 Ω-1 m-1. There is no evidence that the polycrystalline grain structure, 55 nm width and 500–2800 nm length, generates any size-induced electrical effects. The accurate electrical testing of gold nanowires should be significant for nanodevices and nanoelectronics using them as building blocks or interconnects. [ABSTRACT FROM AUTHOR]

Direct measurements on electrical characteristics have been carried out in situ inside a scanning electron microscope using a multiple nanoprobe system on individual SnO2 capped ZnO nanowires (NWs) within a NW film on a Zn substrate. It is shown that while good Ohmic contacts can be made at Zn–ZnO NW and ZnO NW–SnO2 cap (when heavily doped with Zn) junctions, the overall I-V characteristics of the Zn–ZnO–SnO2 junction system differ significantly among different NWs, suggesting doping inhomogeneity in the NW film. [ABSTRACT FROM AUTHOR]

The authors have prepared poly(vinylidenefluoride-trifluoroethylene) Ni/P(VDF-TrFE) nanoscaled coaxial cables with Ni nanowires as the cores and P(VDF-TrFE) nanotubes as the shells by a two-step process. Scanning electron microscope and x-ray diffraction measurements revealed the microstructure and crystallinity of the nanocables. Electrical measurements indicated that the nanocables possessed a large specific capacitance (∼10.84 pC/mm2) and ferroelectric remnant polarization (∼10 μC/cm2) due to the composite structure. The distribution of electrical field in the nanostructure was also analyzed. [ABSTRACT FROM AUTHOR]

The authors demonstrated an investigation of the real-time growth of ZnO nanosheets via in situ observation in an environmental scanning electron microscope. It was found that ZnO nanosheets were grown in a two-stage process: [formula]-oriented nanowires were grown first, and then ZnO nanosheets grew perpendicularly on the parent nanowires along the [0001] axis. The authors’ results revealed that the change of the ZnO growth direction from [formula] (a axis) to [0001] (c axis) can be achieved by control of the growth temperature. [ABSTRACT FROM AUTHOR]

In situ electromigration studies on polycrystalline gold nanowires are performed using a high resolution scanning electron microscope. Simultaneously, the resistance of the gold nanowires is recorded during current stressing. The nanowires are prepared by electron beam lithography (EBL) and subsequent thermal evaporation of gold onto the resist mask. In a further EBL-process contact leads are attached to the gold nanowires to determine resistance changes of better than 5×10-4. The authors observe small resistance oscillations which occur during the scanning process. They show that these oscillations are due to the scanning process of the electron beam rather than founded on periodic changes of the void morphology. [ABSTRACT FROM AUTHOR]

Fe/Pt multilayered nanowires with well-defined interfaces and layer thicknesses were fabricated by a pulse-plating technique in nanoporous anodic alumina templates. The structure, surface morphology, and magnetic properties of the multilayered nanowire arrays have been characterized by x-ray diffractometer, field emission scanning electron microscope, transmission electron microscopy, and superconducting quantum interference device magnetometer. It is found that after being annealed at temperatures of 300 °C, FePt ordered phase with high magnetic anisotropy is formed. This can be explained by rapid diffusion at Fe/Pt interface. [ABSTRACT FROM AUTHOR]

Single-phase Er2SiO5 nanocrystal aggregates were produced on a large scale using Si nanowire (Si-NW) arrays as templates. A dense array of Si-NWs was grown by vapor-liquid-solid mechanism using Au catalyst on Si (111) substrate. Afterwards, ErCl3·6H2O dissolved ethanol solution was spin coated and annealed first at 900 °C for 4 min in a flowing N2/O2 environment and then at 1200 °C in a flowing Ar environment for 3 min. X-ray diffraction, scanning electron microscope, and high-resolution transmission electron microscope measurements indicate that due to the use of Si-NWs, such a short annealing procedure is sufficient to completely transform the Er-coated Si-NWs into a thick, large-area aggregate of pure, single-phase to Er2SiO5 oxyorthosilicate nanocrystals. The crystalline nature of Er2SiO5 film and the loose nature of the aggregate result in an atomlike Er3+ spectrum with a very narrow luminescence linewidth at 1.53 μm, which together with a complete lack of temperature quenching of Er3+ luminescence and a high Er concentration indicate a viability of this method to fabricate efficient, high-gain Si-based optical material for Si photonics. [ABSTRACT FROM AUTHOR]

We present electromigration experiments on single-crystalline silver nanowires. The wires were grown on 4° vicinal silicon (100) substrates by self-organization and were contacted by electron beam lithography. The electromigration experiments were performed in situ in a scanning electron microscope at room temperature with constant dc conditions. In contrast to other experiments we observe void formation at the anode side of the wires. If the current is reversed, the electromigration behavior is also reversed. [ABSTRACT FROM AUTHOR]

We report the electrochemical growth and direct probing of near-vertical gold nanowires several micrometers long that are attached at one end to a substrate. Controllable contact is made to the wires using a straightforward tip-probe arrangement inside a scanning electron microscope. The contact allowed us to perform mechanical and electrical measurements. Through elastic nanowire buckling, we have observed dynamic low-frequency parametric pumping caused by small vibrations of the probe. A numerical simulation of the recorded motion is consistent with an estimated value of Young’s modulus of about 80 GPa, which is close to that of bulk gold. [ABSTRACT FROM AUTHOR]

We prepared W–Ga–C composite contacts on W–Ga–C composite nanowires by focused-ion-beam-induced chemical vapor deposition using a dual-beam scanning electron microscope/focused-ion-beam system. The current-voltage (I-V) characteristics of wires were found to change from nonlinear to linear with increasing wire thickness. For wires with small dimensions, which result in strong nonlinear I-V behavior at room temperature, pairs of contacts were fabricated along the wire under different ion energies and scanning modes. Nonlinear and asymmetric rectifying I-V characteristics were observed. The results suggest that nanoscaled W–Ga–C nanowires may behave similarly to semiconductors and that the contact characteristics may be modified using different deposition conditions. Furthermore, ohmiclike junctions could be formed through the use of specific deposition conditions for the contact pads and nanowires. [ABSTRACT FROM AUTHOR]

β-Ga2O3 nano- and microwires with diameters ranging from tens of nanometers to about one micron and lengths of up to tens of microns, have been obtained by sintering Ga2O3 powder under argon flow. The structures have been investigated by cathodoluminescence in the scanning electron microscope. The samples showed the violet-blue emission characteristic of Ga2O3 and a red emission at 1.73 eV dominant in the nanowires and other nano- and microstructures formed during the sintering treatment. At temperatures below 210 K, this band exhibits sharp peaks separated by 20 meV. This observation suggests the exchange of phonons in the recombination process. [ABSTRACT FROM AUTHOR]

High-density ZnO nanowires (ZnONWs) were aligned onto Au-catalyzed Si substrate through a simple low-temperature physical vapor deposition method. Scanning electron microscope (SEM) observations, x-ray diffraction (XRD) analysis, and photoluminescence spectra showed that the ZnONWs were single-crystalline, with a hexagonal wurzite structure. All of the results inferred from the SEM observations, the XRD rocking curves, and the Raman spectra for the investigated samples confirm that the ZnONWs are well aligned and c-axis oriented. The Raman spectra also indicated that the ZnONWs on Si substrates are under the biaxial compressive stress. Since it takes the advantage of low-cost, easily controlled deposition spot (due to the selective deposition trait of the Au layer), potential for scale-up production, and ability to integrate with Si substrate, this technique has a potential in future for fabricating the ZnONW array-based optoelectronic devices. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Introduces the fabrication of metallic semiconductors in a probing microscope. Advantages of hydrogenated amorphous silicon; Stability of hydrogenated amorphous silicon against oxidation in air; Demonstration of the potentiality of thin films by fabrication of metallic nanowires.

We have studied the electrical transport properties of intrinsic InN nanowires using an electrical nanoprobing technique in a scanning electron microscope environment. It is found that such intrinsic InN nanowires exhibit an ohmic conduction at low bias and a space charge limited conduction at high bias. It is further derived that such InN nanowires can exhibit a free carrier concentration as low as ∼1013 cm-3 and possess a very large electron mobility in the range of 8000-12 000 cm2/V s, approaching the theoretically predicted maximum electron mobility at room temperature. In addition, charge traps are found to distribute exponentially just below the conduction band edge, with a characteristic energy ∼65 meV. [ABSTRACT FROM AUTHOR]

We investigated the timing jitter of superconducting nanowire avalanche photodetectors (SNAPs, also referred to as cascade-switching superconducting single-photon detectors) based on 30-nm-wide nanowires. At bias currents (IB) near the switching current, SNAPs showed sub-35-ps FWHM Gaussian jitter similar to standard 100-nm-wide superconducting nanowire single-photon detectors. At lower values of IB, the instrument response function (IRF) of the detectors became wider, more asymmetric, and shifted to longer time delays. We could reproduce the experimentally observed IRF time-shift in simulations based on an electrothermal model and explain the effect with a simple physical picture. [ABSTRACT FROM AUTHOR]