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Using the thermodynamic density of states, the temperature dependence of the energy density of states in nanowires is investigated. Expressions are derived for the concentration and density of states of a quasi-one-dimensional electron gas. The graphs of the dependence of the concentration and energy density of states for parabolic and nonparabolic dispersion laws on the chemical potential of electrons are presented. The states with parabolic and nonparabolic dispersion laws were compared. The shifts and spread of energy levels are investigated using the thermodynamic density of states. The spreading of energy states was found with increasing temperature. The graphs of the temperature dependence of the energy level of electrons for parabolic and nonparabolic states are presented. Changes in the thermodynamic density of states corresponding to energy levels are depicted as a function of temperature. [ABSTRACT FROM AUTHOR]

Electron transport through a nanostructure in source-drain geometry depends on quantum confinement and quality of metal contacts. In addition, transport mechanism varies with the alignment of the nanostructure between the contacts. For potential applications, thorough understanding of the electrical transport of a single nano object having various orientations on the substrate is important but such kind of probing, especially that of a single vertically aligned nanowire having diameter∼20-100nm >> length, is technically very difficult even via advanced lithographic techniques. Thanks to atomic force microscopy, current-voltage measurements of a quasi-one-dimensional nano-object can be performed using a conductive tip (C-AFM). In the current study, C-AFM has been employed to explore two different transport mechanisms: 1) quantum tunneling in reclined carbon nanotube (CNT) on a conductive surface through the two walls, 2) formation of Schottky barrier in vertical ZnO nanowires due to metal-semiconductor junction. This technique can be employed to probe the defect states and quality of the as-grown nanowires. [ABSTRACT FROM AUTHOR]

A density functional theory (DFT) based computation was conducted to study the electronic band structure, electron density of states (DOS) and partial DOS of CdS/CdSe core/shell nanowires (NW). The band structure calculation shows a direct bandgap of approximately 2.07eV at the Γ-point, using generalized gradient approximation (GGA). The TDOS and PDOS calculations predict that a sharp peak is obtained at -9 eV below the Fermi level, in the valence band (VB) due to the possible hybridization between Se-p, S-p and Cd-s orbitals. Also, the total DOS calculations predict that the conduction band (CB) are mainly dominated by the Cd-s orbitals. Static dielectric constant and refractive index are 2.46 and 1.57 respectively. Absorption spectra show high absorption in the C band of the UV region with a peak at 8.04 eV. The maximum reflectivity of around 24% occurs at around 8.22 eV. And the low values of reflectivity suggests their possible applications as cold anti-reflectors. [ABSTRACT FROM AUTHOR]

This paper presents a simple and fast non-lithographic method to make contacts on a single nanowire. The method involves growth of nanowires, segregation of the desired size nanowire, fabrication of micro-electrodes and placement and alignment of the nanowire on the micro-electrodes. The micro-electrodes were fabricated simply by a cutting tool of few micron thickness to provide a uniform channel of width 10-15 µm. The placement and alignment of the nanowire was obtained by the di-electrophoresis (DEP) method. The I-V characterization of a single CuO nanowire integrated by this method on a gold micro-electrode shows the usual Schottky behavior. Owing to its simplicity and cost advantage, the method has potential to be used as an alternative to lithography based method, for several applications such as gas sensors. [ABSTRACT FROM AUTHOR]

In this work, the effect of electrode materials on the voltage generation as well as the internal resistance of the nanogenerators have been studied. Piezo-electric polycrystalline tetragonal nanowires of Pb(Zr0.52Ti0.48)O3 (PZT) grown by hydrothermal technique were used as the generating material. As an electrode material noble metal gold (Au) as well as copper (Cu) were used. It has been found that the voltage generated by using copper electrode is maximum around ∼1 V. It has also been observed that output power of the nanogenerator enhances from 80 nW to 350 nW with a concomitant reduction of internal resistance. An effective dependence on work function of the electrode material has been established. [ABSTRACT FROM AUTHOR]

Metasurfaces made of arrays of vertically aligned semiconductor nanowires are suitable platforms for light management in optical and photonic applications. Here we report a design approach aimed at engineering the optical behavior of semiconductor nanowire ensembles randomly displaced on the substrate, in order to enhance modulation effects in their optical reflectance response. By resorting to analytical and numerical simulations we demonstrate that the combined implementation of a multi-shell layering together with a tapered designing on the individual nanowire offer new opportunities to tailor the optical reflectance oscillations in this kind of architectures. The simulation insights were compared to experimental results reported for self-assembled GaAs nanowires and GaAs/AlGaAs core-shell nanowires. The proposed approach is especially promising for epitaxially grown semiconductor nanowires, where the suggested design modifications can be easily implemented during the nanostructure growth. [ABSTRACT FROM AUTHOR]

To study the dependency of Debye temperature of nanoparticles of Au, Se, Co and Fe with their size a modest model based on cohesive energy theory has been used. In this project, we have tried to study the variation of Debye temperature of different shape of nanostructured materials such as spherical nanosolid, nanowire and nanofilms of Gold (Au), Selenium(Se), Cobalt(Co), Iron(Fe), Copper(Cu), and Silver(Ag) having their size less than 80 nm. For calculation of Debye temperature of selected samples basic relation of cohesive energy has been used. In our results it is observed that the Debye temperature of selected samples increases rapidly as the particle size reaches below 20 nm. It is due to the fact that the surface atoms are highly unstable at the nanoscale ranges but when size is reduced below 10 nm the most of the atoms lie at the surface. In our results we have also found that, in case of nanofilms there is significant variation of Debye temperature while it is minimum in case of spherical nanosolid. In case of nanowires there is a moderate change in its Debye temperature when its size is reduced. We have compared our computed results with the available experimental data which shows it’s good agreement. [ABSTRACT FROM AUTHOR]

Superconducting single-photon detectors (SNSPD) are receivers in optical systems for space communications and exhibit high quantum efficiency and count rate. The receiver in the optical system of atmospheric communication should provide highly efficient detection of radiation with a wavelength of 1.55 μm. The cut-off wavelength of SNSPD is the maximum wavelength of radiation at which high detection efficiency is maintained and depends on the geometrical parameters of the sensitive element of the detector and the thickness and structure of the thin film of superconducting material parameters. In this work, we simulate the cut-off wavelength depending on the thickness of the superconducting film WxSi1-x and the stoichiometric composition with a nanowire width of 100 nm and a ratio of the bias current to the critical 0.7. It is shown that the largest value of the cut-off wavelength λc = 3.06 μm corresponds to a film thickness of 5 nm and a Si content of 25%. With a film thickness of 7 nm, detection with the required wavelength of 1.55 μm is provided over the entire investigated range of the stoichiometric composition of the film: when the Si content is from 15 to 25%. [ABSTRACT FROM AUTHOR]

In Si nanowire (SiNW) solar cells enhanced light confinement property in addition to decoupling of charge carrier collection and light absorption directions plays a significant role to resolve the draw backs of bulk Si solar cells. In this report we have studied the dependence of the phovoltaic properties of Si NW array solar cells on the SiNW length and enhanced surface defect states as a result of enhanced surface area of the NWs. The SiNW arrays have been fabricated using metal catalyzed electroless etching (MCEE) technique. p-n junction has been produced by spin-ondopant technique followed by thermal diffusion process. Front and rear electrodes have been deposited by e-beam evaporation techniques. SiNW lengths have been controlled from ~ 320 nm to 6.4 μm by controlling the parameters of MCEE technique. Photovoltaic properties of the solar cells have been characterized by measuring quantum efficiency and photocurrent density vs. voltage characteristics. Morphological studies have been carried out by using scanning electron microscopy. Reduction in light trapping capability comes at the benefit of reduced surface defects. The reduction of surface defects has been proved to be more advantageous in comparison to the decrement of light trapping capability. The major contribution to the changes in cell efficiency comes from the enhancement of short circuit current density with a very weak dependence on open circuit voltage. This work is beneficial for the production of commercial Si solar cells where SiNW arrays could be used as an antireflection coating instead of using separate antireflection layers. Thus could reduced the production cost. [ABSTRACT FROM AUTHOR]

In the emerging interdisciplinary field of iontronics, ionic motion and arrangement in electrolyte media are exploited to control the properties and functionalities of electronic devices. This approach encompasses a wide range of applications across engineering and physical sciences including solid-state physics, electronics and energy storage. We briefly discuss the use of approaches and techniques characteristic of iontronics in nanoscale devices based on III-V semiconductor nanostructures, a versatile and promising platform for nanoscience and nanotechnology applications. Then, we report and discuss the operation of InAs nanowire-based electrolyte-gated transistors implemented using ionic liquids. We show that the ionic liquid gating outperforms the conventional solid-state back gate, and we compare the current modulation achieved in the same InAs NW using the ionic liquid gate or the back-gate. Finally, we highlight the capability of the liquid electrolyte to drastically change the resistance dependence on temperature in the nanowire. Our results suggest promising strategies toward the advanced field effect control of innovative III-V semiconductor nanowire-based devices for information and communication technologies at large. [ABSTRACT FROM AUTHOR]

The semiconductor nanowires have promising application in nanotechnology and nano devices. In this paper we have studied the effect of atomic order on the band structure in SiGe nanowires with 4 atoms containing 2 atoms of Si and 2 atoms of Ge. We have considered a structure with square and zigzag cross section. By this study we found that SiGe nanowires with a square cross section is a conductor while SiGe nanowires with zigzag cross section is a semiconductor and their indirect energy band gaps for zigzag A and zigzag B are 0.534 eV and 0.564 eV respectively. From the considered nanowires zigzag A nanowire has highest electronic and thermal conductivity while zigzag B nanowire has lowest electronic and thermal conductivity. [ABSTRACT FROM AUTHOR]

We have studied electronic and thermoelectric properties of ultrathin arsenic nanowire (As-NW) and antimony nanowire (Sb-NW). We have considered linear and rectangular structure of As and Sb. The negative value of binding energy shows its stability for all the structures. Electronic band structure of linear As-NW and Sb-NW shows formation of Dirac cone above Fermi level and quantum conductance of 2G0. Rectangular As-NW and Sb-NW shows band gap of 0.17eV and 0.78eV, respectively. Linear As-NW shows highest electrical and thermal conductivity with a value of 8.45×1019Ω-1m-1s-1 and 0.58×1015Wm-1K-1s-1 at room temperature, respectively. The rectangular Sb-NW shows least electrical and thermal conductivity. Linear structure of Sb-NW shows highest specific heat among the considered NWs. Figure of merit decreases linearly with increase in temperature for rectangular As-NW and Sb-NW while linear As-NW and SbNW shows parabolic variation with temperature. These ultrathin nanowires could emerge as possible applicant in the field of nanoelectronics and thermoelectric devices. [ABSTRACT FROM AUTHOR]

The present study has attempted to investigate the structural, electronic, and optical properties of wurtzite gallium phosphide nanowires by the state-of-the-art Density Functional Theory. The influence of confinement and uniaxial compressive strain on the system properties is studied for understanding the relationship between external strain and corresponding transport mechanism. The electronic band structure of the nanowire (~1 nm) when computed revealed an indirect nature of the band gap that got significantly reduced on increasing the uniaxial compressive strain. Indirect to direct band gap transition is observed when the diameter of the nanowire is increased from ~1 nm to ~ 3 nm. The complex di-electric function computed for analyzing the optical response validates the importance of gallium phosphide nanowires for optoelectronic applications. [ABSTRACT FROM AUTHOR]

In the present paper, we have presented electronic and transport properties of silicon nanowire (SiNW) using density functional theory. Electronic and transport properties are computed for a different diameter of zigzag structure. These nanowires show metallic nature at a nano-scale. With increasing in diameter SiNWs are becoming more metallic. Out of 1R, 2R and 3R zigzag SiNWs, 1R zigzag serves a potential applicant as a electronic and thermal conducting material. [ABSTRACT FROM AUTHOR]

A novel graphene-based waveguide integrated with a stub-nanoresonator loaded with a semiconductor nanowire for control of surface plasmon-polariton propagation has been developed and simulated. [ABSTRACT FROM AUTHOR]

CdTe rectangular nanowire of different diameter in zinc-blende phase is investigated using density functional theory. Enhancement of diameter increased stability and improved electronic qualities suitable for device purpose applications. Cohesive energy per atom enhanced on enlarging diameter advocating the stability. Large diameter nanowire (22.62Å) exhibits bandgap of 1.21eV and electronic effective mass is observed to be 0.51me. The bonding between Cd-Te atoms are predominantly observed as covalent assuring its inertness towards moisture. [ABSTRACT FROM AUTHOR]

In this work, we studied the effect of scattering centers on the electron density profiles of a one dimensional Nanowire channel. Density Matrix Formalism is used for calculating the local electron densities at room temperature. Various scattering centers have been simulated in the channel. The nearest neighbor tight binding method is applied to construct the Hamiltonian of nanoscale devices. We invoke scattering centers by adding local scattering potentials to the Hamiltonian. This analysis could give an insight into the understanding and utilization of defects for device engineering. [ABSTRACT FROM AUTHOR]

We have studied structural phase transition and electronic properties of CdTe nanowires in their wurtzite (B4) to rocksalt (B1) phase by first principles density functional calculations using SIESTA code. Nanowires are derived from wurtzite and rocksalt phase of bulk CdTe with growth direction along 100 planes. We observed structural phase transition from B4→B1 at 4.79 GPa. Wurtzite structure is found to have band gap 2.30 eV while rocksalt is metallic in nature. Our calculated lattice constant (4.55 Å for B4 and 5.84 Å for B1), transition pressure (4.79 GPa) and electronic structure results are in close agreement with the previous calculations on bulk and nanostructures. [ABSTRACT FROM AUTHOR]

We report the synthesis and characterization of pure and Au incorporated Alq3 nanowires. These nanowires are synthesized using thermal vapor transport method. The luminescence intensity of Au incorporated Alq3 nanowires are recorded to be higher than that of pure Alq3 nanowires, which is found to increase with the increase in Au concentration. Fluorescence quenching is also observed when Au concentration is increased beyond the certain limit. [ABSTRACT FROM AUTHOR]

Single nanowire electrode devices have their application in variety of fields which vary from information technology to solar energy. Silver nanowires, made in an aqueous chemical reduction process, can be reacted with gold salt to create bimetallic nanowires. Silver nanowire can be used as electrodes in batteries and have many other applications. In this paper we investigated structural and electronic transport properties of Ag nanowire using density functional theory (DFT) with SIESTA code. Electronic transport properties of Ag nanowire have been studied theoretically. First of all an optimized geometry for Ag nanowire is obtained using DFT calculations, and then the transport relations are obtained using NEGF approach. SIESTA and TranSIESTA simulation codes are used in the calculations respectively. The electrodes are chosen to be the same as the central region where transport is studied, eliminating current quantization effects due to contacts and focusing the electronic transport study to the intrinsic structure of the material. By varying chemical potential in the electrode regions, an I-V curve is traced which is in agreement with the predicted behavior. Bulk properties of Ag are in agreement with experimental values which make the study of electronic and transport properties in silver nanowires interesting because they are promising materials as bridging pieces in nanoelectronics. Transmission coefficient and V-I characteristic of Ag nano wire reveals that silver nanowire can be used as an electrode device. [ABSTRACT FROM AUTHOR]

Nanofibers of polyvinyl alcohol (PVA) containing ammonium molybdate were prepared by a combination of sol-gel and electrospinning techniques. Heat treatment of the as-spun composite nanofibers at 500 °C yielded MoO3 nanowires with a diameter of ∼180 nm. The product was characterized by X-ray diffraction (XRD), scanning electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. XRD and Raman spectra of the heat nanowires clearly show the formation of orthorhombic single phase MoO3 structure without any impurity phases. [ABSTRACT FROM AUTHOR]

Novel, highly sensitive Si-NWs with the length of 200ìm, with size of 15nm were fabricated using basic standard CMOS processes, Reactive ion etching (RIE) and Buffered Oxide Etching (BOE). FESEM micrograph was used to observe the defining and trimming results. With this process, the width of the wires is decreased from the initial, larger 1ìm dimensions to approximately 15nm in a controllable and convenient way. The device is pre-treated with higher pH DI for the mobile carriers to be accumulated at the inner surface of silicon nanowire and nine standard aqueous pH buffer solutions: pH2, pH3, pH 4, pH 5, pH6, pH8 and pH9 were used to test the electrical response of the device. The SiNWs sensor show the highest resistance value for pH 2 and the lowest resistance value for pH 9. In terms of sensitivity, the device with smaller nanowire is found to be more sensitive than larger nanowire as a result of the high surface-to-volume ratio and the measurements were done for 5 times on each sample in 24 hours after the nanowire sensor is immersed in DI water overnight (~24hours), the pH sensitivity is reproduced at every internal. This tendency is repeated in for all the samples. Hence, the fabricated device has demonstrated the potential device in the pH level detection. [ABSTRACT FROM AUTHOR]

We present the synthesis of functionalized-silicon nanowire (f-SiNWs) array which is currently an intense subject of research due to a wide range of opportunities for new generations of nanoscale electronic and optical devices. SiNW arrays were fabricated by a metal-assisted electrodeless wet chemical etching (MEWCE) of highly doped silicon (100) wafers. SiNWs are fabricated at different parameters like etching times, the concentration of chemicals, type of Si wafer, etc. Analysis of various deposition parameters has been carried out to optimize the growth of SiNW. The surface morphology of the etched Si wafer has been carried by electron microscopy. The origin of photoluminescence (PL) in SiNWs has been studied. Phonon confinement effect of functionalization has been analyzed by Raman spectroscopy and PL spectra. [ABSTRACT FROM AUTHOR]

Iron Oxides nanostructures are very promising systems for a new generation of anode material for Lithium-Ion batteries because of their high capacity associated to their surface area. A core-level photoemission study of Fe2O3 nanowires deposited on highly-oriented pyrolitic graphite (HOPG) under Li exposure is presented. The Fe-2p, Fe-3p, and Li-1s core- level lineshape evolution upon Li exposure in ultra-high-vacuum conditions clearly brings to light the Fe ion reduction from fully trivalent to prevalently divalent at saturation. Furthermore, the graphite substrate allows allocation of a large amount of Li ions surrounding the iron-oxide nanowires, opening a new scenario towards the use of graphene for improving the ionic charge exchange. [ABSTRACT FROM AUTHOR]

Zinc Oxide piezoelectric nanowires may offer unprecedented functional properties for piezotronics and piezoelectrics due to their electrical properties combined to the increased strength. Conventional "bulk" modeling used so far has suggested that "the smaller, the better" is the design tenet to obtain stronger and more reliable systems with higher piezopotential and efficacy. However, prior work has never addressed the interaction between electrical and mechanical size-effects of ZnO NWs, particularly the effect of the mechanical stiffening on the piezoelectric potentials and mechanical-to-electrical conversion efficacy of a NW. In this paper we propose a refined "size-dependent" modeling based on a "double power-law scaling" for the mechanical size-effects, which reveals, though consistent simulations based on the Finite Element Method, that stiffening effects can indeed collide with the electrical size-effects in very small NWs, thus meaning that minimizing the NW diameter does not yield always the best piezo-performance, as purported by standard bulk modeling. Our computations support that the elastic size-effects need to be carefully accounted in the design of ZnO NWs piezo-technology. [ABSTRACT FROM AUTHOR]

Indium- Arsenide (InAs) nanowires were grown in a high vacuum chemical beam epitaxy (CBE) unit on InAs(111) wafers substrates at 425- 454oC. Two types of nanogold were used as orientation catalyst, 40nm and 80nm. The measurements were performed using scanning electron microscopy showed that uniform nanowires. The nanowires orient vertically in the InAs nanowire scanning electron microscopy of an array 80nm diameter InAs nanowire with length is in the range 0.5-1 µm and of an array 40nm diameter with length is in the range 0.3-- 0.7 µm. The nanowire length with growth time shows that the linear increase of nanowires start to grow as soon as TMIn is available. The growth rate with temperature was studied. [ABSTRACT FROM AUTHOR]

Parameter variations caused by manufacturing imprecision at the nanoscale are expected to cause large deviations in electrical characteristics of emerging nanodevices and nano-fabrics leading to performance deterioration and yield loss. Parameter variation is typically addressed pre-fabrication, with circuit design targeting worst-case timing scenarios. By contrast, if variation is estimated post-manufacturing, adaptive techniques or reconfiguration could be used to provide more optimal level of tolerance. This paper presents a new on-chip sensor design for nanoscale fabrics that from its own variation, can estimate the extent of systematic variation in neighboring regions. A Monte Carlo simulation framework is used to validate the sensor design. Known variation cases are injected and based on sensor outputs, the extent of systematic variation in physical parameters is calculated. Our results show that the sensor has less than 1.2% error in estimation of physical parameters in 100% of injected variation cases. Based on published experimental data, the sensor estimation is shown to be accurate to within 2% of the actual physical parameter value for a range of up to 7mm. [ABSTRACT FROM PUBLISHER]

A novel graphene waveguide loaded with semiconductor nanowire for control of surface plasmon-polariton propagation has been developed and simulated. [ABSTRACT FROM AUTHOR]

We present a technique to measure gate-controlled photoluminescence (PL) on arrays of semiconductor nanowire (NW) capacitors using a transparent film of Indium-Tin-Oxide (ITO) wrapping around the nanowires as the gate electrode. By tuning the wrap-gate voltage, it is possible to increase the PL peak intensity of an array of undoped InP NWs by more than an order of magnitude. The fine structure of the PL spectrum reveals three subpeaks whose relative peak intensities change with gate voltage. We interpret this as gate-controlled state-filling of luminescing quantum dot segments formed by zincblende stacking faults in the mainly wurtzite NW crystal structure. [ABSTRACT FROM AUTHOR]

We theoretically study the current-phase relation in semiconductor nanowire Josephson junction in the presence of spin-orbit interaction. In the nanowire, the impurity scattering with strong SO interaction is taken into account using the random matrix theory. In the absence of magnetic field, the Josephson current I and phase difference φ between the superconductors satisfy the relation of I(φ) = -I(-φ). In the presence of magnetic field along the nanowire, the interplay between the SO interaction and Zeeman effect breaks the current-phase relation of I(φ) = -I(-φ). In this case, we show that the critical current depends on the current direction, which qualitatively agrees with recent experimental findings. [ABSTRACT FROM AUTHOR]