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Silicon-based photodetectors in photoelectric sensing applications are crucial. In the previous studies of the piezo-phototronic effect on performance modulation of Si/ZnO heterojunctions, the majority is based on a rigid silicon substrate and a ZnO one-dimensional nanostructure, causing incompatibility with advanced semiconductor processing technology as well as the limitation in the field of wearable application. Here, flexible p-Si/n-ZnO film heterojunction photodetectors have been constructed by sputtering ZnO films on chemically thinned Si substrates. Under 405 nm light illumination and at −0.5 V bias, the reverse photocurrent of the heterojunction under the −0.73‰ compression strain increased by 50.36% compared to that under a strain-free state, while the reverse photocurrent for the same device under 0.73‰ tensile strain decreased by 29.2% compared to that under the strain-free state. The introduction of a flexible silicon wafer realizes a bidirectional photocurrent response regulation, which lies in the fact that the strain-induced piezo-potential governs the local energy band structure at the heterojunction interface and, thus, influences the carrier transport in the heterojunction region. The COMSOL simulation results further verify the evolution of the energy band structure at the heterojunction interface at different strain states. This work provides a strategy to design silicon-based optoelectronic devices via the piezo-phototronic effect of a ZnO film.

Using Kelvin probe force microscopy, we studied the contact-electrification (CE) induced charge density on the surfaces of organic–inorganic composite oxide films, such as Nb2O5, ZrO2, and HfO2 films, prepared by a sol–gel method and annealed at different temperatures. The results show that positive triboelectric charges on the film surface gradually turn into negative ones with the increase in the annealing temperature. This phenomenon is attributed to the broken valence bonds between organics and organic–inorganic composites in the film at high temperature, which causes oxygen vacancy defects and consequently changes the surface states of the film. A surface states model is established to understand the process of CE, which further confirms that electron transfer is the dominant mechanism of CE. Moreover, it indicates that in addition to oxygen vacancies, there are also many other factors that can influence CE, including but not limited to non-stoichiometric ratios, impurities, and other types of defects. These factors will modify the surface states through changing the potential barrier energy of the bound electrons on the surface and thus impact the amount and even the direction of electron transfer.

Inspired by the contact-separation mode triboelectric nanogenerator (TENG), we propose a technique for local surface charge density measurement based on atomic force microscopy. It is named as scanning TENG, in which a conductive tip tapping above a charged dielectric surface produces an AC between the tip and the dielectric bottom electrode due to electrostatic induction. The Fourier analysis shows that the amplitude of the first harmonic of the AC is linearly related to surface charge density. The results demonstrate that the scanning TENG is a powerful tool for probing nanoscale charge transfer in contact-electrification.

Rashba spin–orbit coupling (SOC) is a core issue in semiconductor spintronics, which allows the manipulation of electron spin through an electric field rather than an external magnetic field, revealing a bright prospect for advanced electronic devices with ultra-high speed and integration. Conversely, the emerging piezotronic effect is the born characteristic for many semiconductors that have a non-central symmetric structure, such as ZnO and GaN. Here, we design three heterostructure devices, based on piezoelectric p-type (CH3NH3)PbI3 single crystals and n-type wurtzite-structured ZnO thin films, to theoretically study how the piezotronic effect can effectively work on the Rashba spin–orbit coupling. Benefiting from large piezoelectric charges at the interface when a vertical strain is applied, a high concentration of two-dimensional electron gas is induced in the plane of the heterostructure, which can tune the built-in electric field at the interface and further manipulate the Rashba SOC. With the increase in pressure, both the Rashba parameter and spin splitting are found to first vanish and then increase linearly for ZnO with doping densities of 1015 and 1016 cm−3. This work provides insight for manipulating electron spins via the introduction of piezocharges, showing great application potential of the piezotronic effect in tuning spintronic devices.

A triboelectric nanogenerator (TENG), which harvests ubiquitous ambient mechanical energy, is a promising power source for distributed energy. Recently reported new generation direct current TENG (DC-TENG) based on the air breakdown effect exhibits unique advantages over conventional modes of TENG devices, such as free-of-rectification and intrinsic switching behavior. However, owing to different working mechanisms and output characteristics, existing theory and power management strategies are not suitable for in-depth understanding and further advancement of air breakdown DC-TENG. Herein, a theoretical study and experimental verification that systematically investigate the physics, output characteristics, and power management strategy of air breakdown DC-TENG is presented. A general simulation model is then proposed and verified through a statistical analysis method. Contrary to previous understanding of a highly conductive breakdown pathway, a huge resistance is observed and causes inevitable energy loss, which is regarded to be caused by corona discharge. Finally, device optimization and power management strategies are discussed, and fundamental guidance is given for the rational design of air breakdown DC-TENG.

Using high energy X-ray diffraction, we study the phase transition from α to ω in Zr via high-pressure torsion. We examine the evolution of the texture and establish the crystallographic orientation relationship between the α and ω phases. The orientation relationship supports the Silcock/Rabinkim direct transformation pathway and excludes the possibility of transition through the intermediate β phase, the Usikov/Zilbershtein pathway. The texture development in both α and ω phases of Zr during high-pressure torsion is quantified and explained in terms of the dominant slip system and the orientation relationship during martensitic transformation.

By integrating a triboelectric nanogenerator (TENG) and a simple circuit board, the motion of water droplets can be controlled by the output of the TENG, which demonstrates a self-powered microfluidic system toward various practical applications in the fields of microfluidic system and soft robotics. This paper describes a method to construct a physical model for this self-powered system on the basis of electrostatic induction theory. The model can precisely simulate the detailed motion behavior of the droplet under driving of TENG, and it can also reveal the influences of surface hydrophobicity on the motion of the droplet, which can help us to better understand the key parameters that decide the performance of the system. The experimental observation of the dynamic performance of the droplet has also been done with a high speed camera system. A comparison between simulation results and real measurements confirms that the proposed model can predict the velocity and position of the water droplet driven by high voltage source as well as TENG. Hence, the proposed model in this work could serve as a guidance for optimizing the self-powered systems in future studies.

Triboelectric nanogenerators attract more and more research attention, for their high efficiency, low fabrication cost, and high flexibility. However, the mechanism about triboelectrification remains highly debated. In this work, we constructed a liquid-metal based triboelectric nanogenerator (LM-TENG) and investigated the influence of the gas atmosphere on the triboelectrification between the liquid metal and the dielectric materials, such as PTFE, Kapton, and Nylon. It was found that the dielectric materials were negatively charged on contact with the liquid metal in ambient air. But in the nitrogen conditions, the polarity of the charges was reversed. Oxygen was excluded, which is responsible for the polarity reversal in contact electrification. Based on X-ray photoelectron spectroscopy, energy-dispersive X-ray, and SKFM data, a possible mechanism was proposed.

By integrating a triboelectric nanogenerator (TENG) and a thin film dielectric elastomer actuator (DEA), the DEA can be directly powered and controlled by the output of the TENG, which demonstrates a self-powered actuation system toward various practical applications in the fields of electronic skin and soft robotics. This paper describes a method to construct a physical model for this integrated TENG-DEA system on the basis of nonequilibrium thermodynamics and electrostatics induction theory. The model can precisely simulate the influences from both the viscoelasticity and current leakage to the output performance of the TENG, which can help us to better understand the interaction between TENG and DEA devices. Accordingly, the established electric field, the deformation strain of the DEA, and the output current from the TENG are systemically analyzed by using this model. A comparison between real measurements and simulation results confirms that the proposed model can predict the dynamic response of the ...

Amorphization and ultrafine-scale recrystallization within shear bands formed in shock-consolidated Pr2Fe14B∕α‐Fe nanocomposite magnetic powder compacts have been observed using transmission electron microscopy. The shear bands span through multiple grain lengths and truncate preexisting ∼25nm hard and soft magnetic phase grains, resulting in further grain size refinement. The shear bands contain nanocrystallites (

Bimagnetic FePt∕MFe2O4(M=Fe,Co) core∕shell nanoparticles are synthesized via high-temperature solution phase coating of 3.5nm FePt core with MFe2O4 shell. The thickness of the shell is controlled from 0.5 to 3nm. An assembly of the core∕shell nanoparticles shows a smooth magnetization transition under an external field, indicating effective exchange coupling between the FePt core and the oxide shell. The coercivity of the FePt∕Fe3O4 particles depends on the volume ratio of the hard and soft phases, consistent with previous theoretical predictions. These bimagnetic core∕shell nanoparticles represent a class of nanostructured magnetic materials with their properties tunable by varying the chemical composition and thickness of the coating materials.

Pr2Fe14B/α-Fe based nanocomposites have been prepared through crystallization of melt-spun amorphous Pr7Tb1Fe85Nb0.5Zr0.5B6 ribbons by means of ac Joule heating while simultaneously monitoring room-temperature electrical resistance R. The R value shows a strong variation with respect to applied current I, and is closely related to the amorphous-to-nanocrystalline phase transformation. The curve of R versus I allows one to control the crystallization behavior during Joule heating and to identify the heat-treatment conditions for optimum magnetic properties. A coercivity of 550 kA/m and a maximum energy product of 128 kJ/m3 have been obtained upon heating the amorphous ribbons at a current of 2.0 A. These properties are around 30% higher than the values of samples prepared by conventionally (furnace) annealed amorphous ribbons.

Polar surface dominated ZnO nanopropeller arrays were synthesized by a two-step high temperature solid-vapor deposition process. The axis of the nanopropellers is a straight nanowire along the c axis and enclosed by {2110} surfaces, which grew first; the sixfold symmetric nanoblades are later formed along the crystallographic equivalent a axes (〈2110〉) perpendicular to the nanowire; and the array is formed by epitaxial growth of nanoblades on the nanowire. The top surface of the nanoblade is the Zn terminated +c plane, showing surface steps and possible secondary growth of nanowires due to higher self-catalytic activity, while the back surface is the oxygen-terminated −c plane, which is smooth and inert.

We report the controlled synthesis of free-standing ZnO nanobelts whose surfaces are dominated by the large polar surfaces. The nanobelts grow along the a axis, their large top/bottom surfaces are the ±(0001) polar planes, and the side surfaces are (0110). Owing to the positive and negative ionic charges on the zinc- and oxygen-terminated ±(0001) surfaces, respectively, the nanobelts form multiloops of nanohelixes/nanosprings/nanospirals for the sake of reducing electrostatic energy introduced by the polar surfaces as well as balancing the difference in surface tension. The polar surface dominated ZnO nanobelts are likely to be an ideal system for understanding piezoelectricity and polarization induced phenomena at nanoscale.

Zinc oxide (ZnO) nanobelts synthesized by thermal evaporation have been ion implanted with 30 keV Mn+ ions. Both transmission electron microscopy and photoluminescence investigations show highly defective material directly after the implantation process. Upon annealing to 800 °C, the implanted Mn remains in the ZnO nanobelts and the matrix recovers both in structure and luminescence. The produced high-quality ZnO:Mn nanobelts are potentially useful for spintronics.

Recently, the piezotronic effect has been observed in two-dimensional single-layer MoS2 materials, which have potential applications in force and pressure triggered or controlled electronic devices, sensors, and human-machine interfaces. However, classical theory faces the difficulty in explaining the mechanism of the piezotronic effect for the top- and enclosed-contacted MoS2 transistors, since the piezoelectric charges are assumed to exist only at the edge of the MoS2 flake that is far from the electronic transport pathway. In the present study, we identify the piezoelectric charges at the MoS2/metal-MoS2 interface by employing both the density functional theory and finite element method simulations. This interface is on the transport pathway of both top- and enclosed-contacted MoS2 transistors, thus it is capable of controlling their transport properties. This study deepens the understanding of piezotronic effect and provides guidance for the design of two-dimensional piezotronic devices.

Nanobelts are a group of materials that have a rectangle-like cross section with typical widths of several hundred nanometers, width-to-thickness ratios of 5–10, and lengths of hundreds of micrometers. In this letter, nanoindentations were made in individual ZnO and SnO2 nanobelts by a cube corner diamond indenter. It is shown that the effect of indentation size is still obvious for indentation depths less than 50 nm. It is also demonstrated that nanomachining of nanobelts is possible using an atomic force microscope tip.

The mechanical resonance of a single ZnO nanobelt, induced by an alternative electric field, was studied by in situ transmission electron microscopy. Due to the rectangular cross section of the nanobelt, two fundamental resonance modes have been observed corresponding to two orthogonal transverse vibration directions, showing the versatile applications of nanobelts as nanocantilevers and nanoresonators. The bending modulus of the ZnO nanobelts was measured to be ∼52 GPa and the damping time constant of the resonance in a vacuum of 5×10−8 Torr was ∼1.2 ms and quality factor Q=500.

Self-assembly of FePt and Fe3O4 nanoparticles of different sizes led to various FePt–Fe3O4 nanocomposites. Annealing the composite under reducing atmosphere at 650 and 700 °C induced magnetically hard FePt phase and magnetically soft Fe3Pt phase. The FePt and Fe3Pt phases were either linked by a common interface or coexisted within one grain as domains with sizes

Semiconducting oxide nanobelts of ZnO have been sectioned and manipulated, for microelectromechanical systems, using an atomic force microscopy probe. Structurally modified nanobelts demonstrate potential for nanocantilever based technologies. With dimensions ∼35–1800 times smaller than conventional cantilevers, the nanocantilevers are expected to have improved physical, chemical, and biological sensitivity for scanning probe microscopy and sensor applications.

Gas sensors have been fabricated using the single-crystalline SnO2 nanobelts. Electrical characterization showed that the contacts were ohmic and the nanobelts were sensitive to environmental polluting species like CO and NO2, as well as to ethanol for breath analyzers and food control applications. The sensor response, defined as the relative variation in conductance due to the introduction of the gas, is 4160% for 250 ppm of ethanol and −1550% for 0.5 ppm NO2 at 400 °C. The results demonstrate the potential of fabricating nanosized sensors using the integrity of a single nanobelt with a sensitivity at the level of a few ppb.

We report on measurements of the plasmon losses of individual single-wall carbon nanotubes by electron energy-loss spectroscopy in a high-resolution transmission electron microscope. The experimental data are compared to simulated excitation probabilities calculated using the hydrodynamic theory of the interaction between a probe electron and a two-dimensional quasifree electron gas confined on a cylindrical shell. Depending on the nanotube geometry, the first- or the second-order oscillation mode dominates the loss spectrum. The resonance energy of the dominant resonance mode is found to depend on the radius of the nanotube.

We have produced exchange-coupled FePt nanoparticle assemblies by chemical synthesis and subsequent thermal annealing. As the interparticle distances decrease by tuning the annealing conditions, interparticle interactions change from dipolar type to exchange type, and the magnetization reversal mechanism switches from rotation controlled to domain-nucleation controlled. With increasing annealing temperature, the coercivity first increases due to improved chemical ordering, and then drops significantly, resulting from excessive interparticle exchange coupling. For the samples exhibiting exchange coupling, both the remanence ratio and coercive squareness increase.

Ultrathin films (

Field emission of individual carbon nanotubes was observed by in situ transmission electron microscopy. A fluctuation in emission current was due to a variation in distance between the nanotube tip and the counter electrode owing to a “head-shaking” effect of the nanotube during field emission. Strong field-induced structural damage of a nanotube occurs in two ways: a piece-by-piece and segment-by-segment pilling process of the graphitic layers, and a concentrical layer-by-layer stripping process. The former is believed owing to a strong electrostatic force, and the latter is likely due to heating produced by emission current that flowed through the most outer graphitic layers.

β-PbO2 nanobelts, with a rectangular cross section, a typical length of 10–200 μm, a width of 50–300 nm, and a width-to-thickness ratio of 5–10, have been successfully synthesized by simple elevated evaporation of commercial PbO powders at high temperature. The PbO2 nanobelts are enclosed by top surfaces ±(201) and side surfaces ±(101) and their growth direction is [010]. Each PbO2 nanobelt is found to have a large polyhedral Pb tip at one of its ends, suggesting the growth is dominated by a vapor–liquid–solid mechanism. Electron beam irradiation of the PbO2 nanobelts results in the phase transformation from PbO2 to PbO and finally to Pb.

The work function at the tips of individual multiwalled carbon nanotubes has been measured by an in situ transmission electron microscopy technique. The tip work function shows no significant dependence on the diameter of the nanotubes in the range of 14–55 nm. Majority of the nanotubes have a work function of 4.6–4.8 eV at the tips, which is 0.2–0.4 eV lower than that of carbon. A small fraction of the nanotubes have a work function of ∼5.6 eV, about 0.6 eV higher than that of carbon. This discrepancy is suggested due to the metallic and semiconductive characteristics of the nanotube.

A configuration of misfit dislocation dipoles is observed in a Ga0.5In0.5P heterostructure grown by solid-source molecular-beam epitaxy on GaAs. The dipole dislocations are mostly of 60° type, separated by ∼3.5 nm. The dislocations are not produced by conventional lattice mismatch, rather, they could be the result of lateral compositional modulation in the Ga0.5In0.5P epilayer.

Recent interest in the growth of aligned carbon nanotube films using transition metal catalysts has led to questions concerning the growth mechanism involved. In our experiment carbon tubules grown using Ni catalysts exhibit a preferred orientation relative to the catalytically active surfaces of Ni. The axial directions of the tubular structure are mainly parallel to the 〈110〉 and 〈042〉 directions of Ni. The faceted shape of the Ni particles determines the intrinsic structure of the tubules. A mechanism involving spiral growth is proposed to explain the nucleation and growth of such tubules.

Electron energy-loss spectroscopy studies are reported on three different types of structures: solid silica spheres, mesoporous silica, and the double length-scale ordered (DLSO) porous silica. The mesoporous silica has porosity at the length scale of nanometers. The DLSO porous silica has an additional ordering on submicron hollows created by the template polystyrene spheres. The plasmon energy of the porous silica shows a significant shift in comparison to that of the bulk, suggesting that the local density of the bound electrons in the porous structures is lower than that in the bulk. This gives the possibility of tuning the electronic structure of silica by varying its porosity, leading to even lower dielectric loss.

A blue emission powder phosphor Sr2CeO4 for field emission displays was prepared using a chemical coprecipitation technique, which is most suitable for large-scale production. The powders were fired at different temperatures to optimize the properties. Firing the powder at 1200 °C for 2 h gave the highest luminescence efficiency of 5.4 lm/W at 4 kV and 29.0 lm/W at 10 kV. The emission peak of this phosphor is at ∼470 nm and Commission International de l’Eclairage coordinates are x=0.19, y=0.26.

The piezotronic effect uses strain-induced piezoelectric charges at interfaces and junctions to tune and/or control carrier transport in piezoelectric semiconductor devices. This effect has recently been observed in single-layer 2D MoS2 materials. However, previous work had found that metallic states are generated at the edge of a free-standing MoS2 flat sheet, and these states may screen the piezoelectric charges. Using density functional theory simulations, we found that the metal–MoS2 interface structure plays an important role in enhancing both the piezoelectric and piezotronic effects in MoS2 transistors by breaking the metallic state screening effect at the MoS2 edge. This study not only provides an understanding of the piezoelectric and piezotronic effects based on first principles calculations but also offers guidance for the design of two-dimensional piezotronic devices.

Using the white line intensities, electron energy-loss spectroscopy in a transmission electron microscope has been employed to characterize the valence conversion and oxygen vacancies in La1−xCaxMnO3−y. For a nominal doping composition x=0.33, the ratio of Mn4+ to Mn3+ is determined to be more than 0.25 but less than 0.5, and the content of oxygen vacancy y is no more than 0.065 (equivalent to 2.2 at. % of the oxygen content). At ymax=0.065, 60% of the residual charge introduced by Ca doping is balanced by the conversion of Mn3+to Mn4+ and 40% by oxygen vacancy.

This work establishes the stability at elevated temperatures of columnar defects, artificially formed in the Bi‐based cupric oxide superconductor Bi2Sr2Ca1Cu2O8 for enhanced vortex pinning. Isochronal anneals, conducted in air, led to losses of critical current density in two stages. The defects were relatively stable up to ∼550 °C, where second stage annealing began; above this, the pinning diminished rapidly. The recrystallization and loss of columnar defects were corroborated by transmission electron microscopy.

BaTiO3 thin films were grown epitaxially on (100) MgO substrates by metalorganic chemical vapor deposition (MOCVD) at a temperature of 600 °C. This substrate temperature is the lowest reported temperature for the growth of epitaxial BaTiO3 films by an MOCVD process. The films had a cube–cube orientation relationship with the substrate and were oriented with an a‐axis perpendicular to the substrate plane. Nanoscale energy dispersive x‐ray spectrometry measurements showed no evidence of interdiffusion between the film and substrate.

A possible microstructural origin of the high critical current densities which have been obtained in c‐axis‐aligned, polycrystalline TlBa2Ca2Cu3O8+x deposits has been identified. The results of x‐ray diffraction determinations of basal plane texture of Tl‐1223 deposits prepared by spray pyrolysis are observed to depend on the size of the x‐ray beam. Furthermore, most grain boundaries were found from transmission electron microscopy to have small misorientation angles. It is concluded that although overall the basal plane orientations are nearly random, there is a high degree of local texture indicative of colonies of similarly oriented grains. The spread in a‐axis orientation within a colony is ∼10°–15°. Intercolony conduction, it is suggested, may be enhanced by a percolative network of small‐angle grain boundaries at colony interfaces.

Using the full potential linearized augment plane wave method with the modified Becke and Johnson (mBJ) potential, the half-metallicity and electronic structure for the wurtzite ScM (M = C, Si, Ge, and Sn) compounds are investigated. The ScM series compounds are found to be excellent half-metallic ferromagnets (HMFs) with large half-metallic gaps (0.76–0.33 eV). The magnetic moments are 2.00 μB per cell, and p-d hybridization mechanism plays crucial role in forming the half-metallic ferromagnetism. The ferromagnetic ground states, larger half metallic gaps, the robust half-metallicity with respect to the lattice compression, negative cohesive energy, and heat of formation indicate ScM compounds would be promising HMFs.

Core-shelled multimetallic nanoparticles have unique catalytic properties compared to their single-element counterparts. Due to the different lattice parameters of the core and shell, the strain field is built up at the interface between the two phases. As for thin films, a formation of misfit and threading dislocations is an approach to release interface strain. However, for two-phase nanoparticles especially when their sizes are at nanometer scale, their dislocation formation in the volume remains to be investigated owing to the large surface-to-volume ratio. Here, we confirmed the existence of dislocations in the Au-FePt core-shelled nanoparticles of sizes less than 10 nm. It is suggested that the different atom sizes of the core and the shell materials are likely to be a key factor to generate and lock dislocations inside the nanoparticles.

The effect of metal coating on the photoluminescence (PL) properties of ZnO nanowire arrays has been investigated in detail in this letter. The Zn coating induces remarkable enhancement of the ultraviolet and green emissions of the nanowires, while the deposition of Ag leads to notable decrement of them. A model considering the type of contacts formed between metals and ZnO is proposed to interpret the change of the PL spectra. Also, this model is strongly supported by the PL variation of the nanowires after coating with other kinds of metals.

Multi-segment silicon nanocones were designed and fabricated to investigate their growth kinetics. We found the ambient gas influenced the growth rates of Si nanocones remarkably. The axial growth rate increased with the total pressure of ambient gas, finally approaching saturation. Meanwhile the radial growth rate also increased with the total pressure but decreased with hydrogen content. A model was developed to study the growth kinetics by combining the effects of Langmuir adsorption, silane decomposition, and hydrogen coverage on the surface of SiNCs, which agreed with the experimental results. This paper also demonstrated the controllable cone angles by the ambient gas.

We present a study on the effect of deformation induced piezoelectric potential (piezopotential) in a ZnO micro/nanowire on its electrical transport properties by choosing different contacting locations on the wire to form a metal-ZnO contact. When a ZnO wire is under nonuniform deformation, the local piezopotential distribution at different positions shows significant effect on and distinct trend of variation in the charge carrier transport characteristic. This study has a broad impact on understanding the characteristics of piezotronic devices based on nanowires of wurtzite materials by controlling local contact position and contact size.

In this report, we find multilayered graphene, which has good transparency, conductivity and suitable work function, can be used as the anode for the organic light emitting device. Our device structure is Al/glass/multilayered graphene/V2O5/NPB/CBP:(ppy)2Ir(acac)/Bphen/Bphen:Cs2CO3/Sm/Au. The maximum luminance efficiency and maximum power efficiency reach 0.75 cd/A and 0.38 lm/W, respectively. We believe that by optimizing the hole density and uniforming the thickness of the multilayered graphene anode, the device efficiency can be remarkably increased in the future.

The Schottky contact based photon detection was demonstrated using CdS (visible light responsive), silicon (indirect n-type oxygen-non-adsorbing), and CuO (indirect p-type oxygen-adsorbing) nanowire nanosensors. With changing one of the two nanowire-electrode contacts from ohmic to Schottky, detection sensitivities as high as 105% were achieved by the CdS nanowire nanosensor operated at the reverse bias mode of −8 V, which was 58 times higher than that of the corresponding ohmic contact device. The reset time was also significantly reduced. In addition, originally light nonresponsive silicon and CuO nanowires became light responsive when fabricated as a Schottky contact device. These improvements in photon detection can be attributed to the Schottky gating effect realized in the present nanosensor system by introducing a Schottky contact.

We have utilized the limited penetration depth of x-rays to study the near-surface properties of vertically aligned ZnO nanowires. For an energy of 600 eV the penetration depth varies between 3 and 132 nm as the incidence angle changes from 2° to 33°. Thus, by obtaining optical luminescence spectra as a function of incidence angle, it is possible to probe the near-surface region with nanometer-scale resolution. We will present angle dependent optical luminescence data from oriented ZnO nanowires. By fitting the results to a simple model, we extract a depth for the surface defect regions of ∼14 nm.

We present a method, polarized Raman (PR) spectroscopy combined with atomic force microscopy (AFM), to characterize in situ and nondestructively the structure and the physical properties of individual nanostructures. PR-AFM applied to individual ZnO nanobelts reveals the interplay between growth direction, point defects, morphology, and mechanical properties of these nanostructures. In particular, we find that the presence of point defects can decrease the elastic modulus of the nanobelts by one order of magnitude. More generally, PR-AFM can be extended to different types of nanostructures, which can be in as-fabricated devices.