Nanowire Research Papers - Academia.edu (original) (raw)

We studied the morphology, structure, and magnetic properties of Fe nanowires that were electrodeposited as a function of the electrolyte temperature. The nucleation mechanism followed instantaneous growth. At low temperatures, we... more

We studied the morphology, structure, and magnetic properties of Fe nanowires that were electrodeposited as a function of the electrolyte temperature. The nucleation mechanism followed instantaneous growth. At low temperatures, we observed an increase of the total charge reduced into the templates, thus suggesting a significant increase in the degree of pore filling. Scanning electron microscopy images revealed smooth nanowires without any characteristic features that would differentiate their morphology as a function of the electrolyte temperature. X-ray photoelectron spectroscopy studies indicated the presence of a polycarbonate coating that covered the nanowires and protected them against oxidation. The X-ray diffraction measurements showed peaks coming from the polycrystalline Fe bcc structure without any traces of the oxide phases. The crystallite size decreased with an increasing electrolyte temperature. The transmission electron microscopy measurements proved the fine-crystal...

The demand projected in the world's population growth emphasis the advent of new technologies in the areas of energy consumption, environmental changes, and biomedical applications which play a major part in human life. One promising... more

The demand projected in the world's population growth emphasis the advent of new technologies in the areas of energy consumption, environmental changes, and biomedical applications which play a major part in human life. One promising technology that fulfills the above demand is nanosciences and nanotechnology which play a crucial role at the nanoscale in energy, environment, and Lifesciences. Nanosciences plays a vital role in environmental monitoring, energy conversion, distribution, and storage as well as useful in gene therapy, drug delivery systems, and tissue engineering. The use of nanoscale materials and nanoparticles in these arenas eases the process flow and cost-effective with ecofriendly over the current conventional methods or applications. The various applications of nanosciences and Nanobiotechnology are versatile and find their applications in the fields of human diagnostics, bioremediation, waste management, medical devices, tissue engineering, green technology, environmental monitoring, emission control, electricity production and transmission loss, solar power, etc.

Commonly used transistors are based on the use of semiconductor junctions formed by introducing doping atoms into the semiconductor material. As the distance between junctions in modern devices drops below 10 nm, extraordinarily high... more

Commonly used transistors are based on the use of semiconductor junctions formed by introducing doping atoms into the semiconductor material. As the distance between junctions in modern devices drops below 10 nm, extraordinarily high doping concentration gradients become necessary. For this reason, a new device was proposed which has full CMOS functionality and is made by using junctionless nanowires. They have near-ideal sub-threshold slope, extremely low leakage currents and less degradation of mobility with gate voltage and temperature than classical transistors. Among several types of field effect transistors, gate-all-around junctionless nanowire FET (GAA-JL-NW-FET) is the recently invented one. In this article, temperature dependency of threshold voltage of GAA-JL-NW-FET has been analyzed for different channel materials such as Si, GaAs, InAs and InP. From the simulation result, it is observed that the threshold voltage is minimum for InAs and it decreases when the temperature is increased for all the above mentioned channel materials.

Highly hexagonally ordered hard anodic aluminum oxide membranes, which have been modified by a thin cover layer of SiO2 deposited by atomic layer deposition method, were used as templates for the synthesis of electrodeposited magnetic... more

Highly hexagonally ordered hard anodic aluminum oxide membranes, which have been modified by a thin cover layer of SiO2 deposited by atomic layer deposition method, were used as templates for the synthesis of electrodeposited magnetic Co-Ni nanowire arrays having diameters of around 180 to 200 nm and made of tens of segments with alternating compositions of Co54Ni46 and Co85Ni15. Each Co-Ni single segment has a mean length of around 290 nm for the Co54Ni46 alloy, whereas the length of the Co85Ni15 segments was around 430 nm. The composition and crystalline structure of each Co-Ni nanowire segment were determined by transmission electron microscopy and selected area electron diffraction techniques. The employed single-bath electrochemical nanowire growth method allows for tuning both the composition and crystalline structure of each individual Co-Ni segment. The room temperature magnetic behavior of the multisegmented Co-Ni nanowire arrays is also studied and correlated with their structural and morphological properties.

— This paper reports various optimization aspects of an ambipolar silicon nanowire field-effect transistor with high-κ source–drain (S/ D) spacer using coupled 3-D Technology Computer Aided Design numerical device simulations. The impact... more

— This paper reports various optimization aspects of an ambipolar silicon nanowire field-effect transistor with high-κ source–drain (S/ D) spacer using coupled 3-D Technology Computer Aided Design numerical device simulations. The impact of variation in device features, such as spacer material type and length of spacer (L sp), gate dielectric and its thickness (t ox) and intergate distance (d G1G2) on vital performance parameters of the device, such as I ON , I ON /I OFF , Subthreshold swing (S/S), V t , and g m /I d , is investigated and analyzed. It is observed that increasing the spacer length increases Band to band tunneling rate probability through the thin barriers at ON-state. Moreover, the permittivity of spacer material is found to be closely related to the lateral fringe lines emanated from gate, resulting in a boosted I ON as well as g m /I d at higher κ sp. Scaling down the thickness of gate oxide is not found to be a good idea, as it causes a reduction in ON–OFF current ratio though S/S remains mostly unaffected. However, intergate distance scaling is found to have a strong influence on device performance providing higher current drive and lower S/S for both n-and p-programs at lower d G1G2 .

Progress in the terahertz (THz) region of the electromagnetic spectrum is undergoing major advances, with advanced THz sources and detectors being developed at a rapid pace. Yet, ultrafast THz communication is still to be realized, owing... more

Progress in the terahertz (THz) region of the electromagnetic spectrum is undergoing major advances, with advanced THz sources and detectors being developed at a rapid pace. Yet, ultrafast THz communication is still to be realized, owing to the lack of practical and effective THz modulators. Here, we present a novel ultrafast active THz polarization modulator based on GaAs semiconductor nanowires arranged in a wire-grid configuration. We utilize an optical pump-terahertz probe spectroscopy system and vary the polarization of the optical pump beam to demonstrate ultrafast THz modulation with a switching time of less than 5 ps and a modulation depth of -8 dB. We achieve an extinction of over 13% and a dynamic range of -9 dB, comparable to microsecond-switchable graphene- and metamaterial-based THz modulators, and surpassing the performance of optically switchable carbon nanotube THz polarizers. We show a broad bandwidth for THz modulation between 0.1 and 4 THz. Thus, this work present...

The combination of electrodeposition and polymeric templates created by heavy-ion irradiation followed by chemical track etching provides a large variety of poly- and single-crystalline nanowires of controlled size, geometry, composition,... more

The combination of electrodeposition and polymeric templates created by heavy-ion irradiation followed by chemical track etching provides a large variety of poly- and single-crystalline nanowires of controlled size, geometry, composition, and surface morphology. Recent results obtained by our group on the fabrication, characterization and size-dependent properties of nanowires synthesized by this technique are reviewed, including investigations on electrical resistivity, surface plasmon resonances, and thermal instability.

Cathodoluminescence (CL) is a powerful tool for the investigation of optical properties of materials. In recent years, its combination with scanning transmission electron microscopy (STEM) has demonstrated great success in unveiling new... more

Cathodoluminescence (CL) is a powerful tool for the investigation of optical properties of materials. In recent years, its combination with scanning transmission electron microscopy (STEM) has demonstrated great success in unveiling new physics in the field of plasmonics and quantum emitters. Most of these results were not imaginable even twenty years ago, due to conceptual and technical limitations. The purpose of this review is to present the recent advances that broke these limitations, and the new possibilities offered by the modern STEM-CL technique. We first introduce the different STEM-CL operating modes and the technical specificities in STEM-CL instrumentation. Two main classes of optical excitations, namely the coherent one (typically plasmons) and the incoherent one (typically light emission from quantum emitters) are investigated with STEM-CL. For these two main classes, we describe both the physics of light production under electron beam irradiation and the physical basis for interpreting STEM-CL experiments. We then compare STEM-CL with its better known sister techniques: scanning electron microscope CL, photoluminescence, and electron energy-loss spectroscopy. We finish by comprehensively reviewing recent STEM-CL applications.

ABSTRACT Silicon nanowire (SiNW) field effect transistors (FETs) have been widely investigated as biological sensors for their remarkable sensitivity due to their large surface to volume ratio (S/V) and high selectivity towards a myriad... more

ABSTRACT Silicon nanowire (SiNW) field effect transistors (FETs) have been widely investigated as biological sensors for their remarkable sensitivity due to their large surface to volume ratio (S/V) and high selectivity towards a myriad of analytes through functionalization. In this work, we propose a long channel (L > 500 nm) junctionless nanowire transistor (JNT) SiNW sensor based on a highly doped, ultrathin body field-effect transistor with an organic gate dielectric εr = 1.7. The operation regime (threshold voltage Vth) and electrical characteristics of JNTs can be directly tuned by the careful design of the NW/Fin FET. JNTs are investigated through 3D Technology Computer Aided Design (TCAD) simulations performed as a function of geometrical dimensions and channel doping concentration Nd for a p-type tri-gated structure. Two different materials, namely, an oxide and an organic monolayer, with varying dielectric constants εr provide surface passivation. Mildly doped Nd = 1 × 1019 cm−3, thin bodied structures (fin width Fw < 20 nm) with an organic dielectric (εr = 1.7) were found to have promising electrical characteristics for FET sensor structures such as Vth ~ 0 V, high relative sensitivities in the subthreshold regime S > 95%, high transconductance values at threshold gm,Vfg=0 V > 10 nS, low subthreshold slopes SS ~ 60 mV/dec, high saturation currents Id,max ~ 1–10 μA and high Ion/Ioff > 104–1010 ratios. Our results provide useful guidelines for the design of junctionless FET nanowire sensors that can be integrated into miniaturized, low power biosensing systems.

This research paper explains the effect of the dimensions of Gate-all-around Si nanowire tunneling field effect transistor (GAA Si-NW TFET) on ON/OFF current ratio, drain induces barrier lowering (DIBL), sub-threshold swing (SS), and... more

This research paper explains the effect of the dimensions of Gate-all-around Si nanowire tunneling field effect transistor (GAA Si-NW TFET) on ON/OFF current ratio, drain induces barrier lowering (DIBL), sub-threshold swing (SS), and threshold voltage (VT). These parameters are critical factors of the characteristics of tunnel field effect transistors. The Silvaco TCAD has been used to study the electrical characteristics of Si-NW TFET. Output (gate voltage-drain current) characteristics with channel dimensions were simulated. Results show that 50nm long nanowires with 9nm-18nm diameter and 3nm oxide thickness tend to have the best nanowire tunnel field effect transistor (Si-NW TFET) characteristics.

Electrodeposition is emerging as a method for the synthesis of semiconductor thin films and nanostructures. In this work we prepared the nanocrystalline CdTe thin films on indium tin oxide coated glass substrate from aqueous acidic bath... more

Electrodeposition is emerging as a method for the synthesis of semiconductor thin films and nanostructures. In this work we prepared the nanocrystalline CdTe thin films on indium tin oxide coated glass substrate from aqueous acidic bath at the deposition temperature 50 ± 1 °C. The films were grown potentiostatically from −0.60 V to −0.82 V with respect to saturated calomel reference electrode. The structural, compositional, morphological and optical properties were investigated using X-ray diffraction (XRD), energy dispersive analysis by X-rays (EDAX), atomic force microscopy (AFM), and UV–vis spectroscopy respectively and cyclic voltammetery. The structural and optical studies revealed that films are nanocrystalline in nature and possess cubic phase, also the films are preferentially oriented along the cubic (1 1 1) plane. The effect of cadmium composition on the deposited morphology was also investigated. The size dependent blue shift in the experimentally determined absorption edge has been compared with the theoretical predictions based on the effective mass approximation and tight binding approximation. It is shown that the experimentally determined absorption edges depart from the theoretically calculated values.

The authors report the nanomachining of sub-20-nm wide doubly clamped silicon carbon nitride resonators using low keV electron beam lithography with polymethyl methacrylate resist and cold development. Methodologies are developed for... more

The authors report the nanomachining of sub-20-nm wide doubly clamped silicon carbon nitride resonators using low keV electron beam lithography with polymethyl methacrylate resist and cold development. Methodologies are developed for precisely controlling the resonator widths in the ultranarrow regime of 11–20 nm. Resonators with lengths of 1–20 μm and widths of 16–280 nm are characterized at room temperature in vacuum using piezoelectric actuation and optical interferometry. Clamping and surface losses are identified as the dominant energy loss mechanisms for a range of resonator widths. The resonator clamping points are optimized using an original electron beam lithography simulator. Various alternative clamping point designs are also modeled and fabricated in order to reduce the clamping losses.

We have investigated electrical and magnetic properties of single-crystalline Fe5Si3 nanowires. The nanowire ensemble shows ferromagnetic properties with a high Tc of 380 K, small coercivity, and no remanence in zero field at room... more

We have investigated electrical and magnetic properties of single-crystalline Fe5Si3 nanowires. The nanowire ensemble shows ferromagnetic properties with a high Tc of 380 K, small coercivity, and no remanence in zero field at room temperature. Such magnetic properties of the single-crystalline nanowires should give a chance to realize not only novel nanospintronic devices but also biomedical applications. Electrical transport measurements on single Fe5Si3 nanowire device show metallic properties with low resistivity of 487 μ ·Ω· cm. Fe5Si3 nanowires are the first example of single-crystalline metallic ferromagnet with a Tc higher than room temperature.

A bioanode for glucose based biofuel cell have been fabricated by combining glucose oxidase and highly ordered Palladium (Pd) nanowire array electrode. The Pd nanowires were 5.57 μm in length and 64.28 nm in diameter. The hydrogel... more

A bioanode for glucose based biofuel cell have been fabricated by combining glucose oxidase and highly
ordered Palladium (Pd) nanowire array electrode. The Pd nanowires were 5.57 μm in length and 64.28 nm in
diameter. The hydrogel composite modified Pd nanowire array bioanodes were characterized with cyclic voltammetry
in the presence of different scan rates and different substrate concentrations under physiological conditions. The
electrochemical measurements showed a linear amperometric response in the range of 1 mM to 13 mM. In addition,
surface and structural characterization were performed by scanning electron microscopy leading to the conclusion
that the Pd nanowires are highly ordered and vertically aligned and thereby promotes the number of electroactive
sites for the catalysis of the oxidation of glucose. The combination of glucose oxidase and Pd nanowire arrays
revealed the capability of these enzymatic bioanodes to perform direct electron transfer to Pd nanostructure surfaces
and be used in a glucose biofuel cell.

It is crucial to examine the dependence of photoelectric parameters of solar cells on the light incidence angle. In the present study, two solar cell models have been developed using the Sentaurus Technology Computer-Aided Design software... more

It is crucial to examine the dependence of photoelectric parameters of solar cells on the light incidence angle. In the present study, two solar cell models have been developed using the Sentaurus Technology Computer-Aided Design software package. The light spectrum AM1.5 has been directed on the frontal surface of solar cells at different angles. It has been found that the angular coefficient of the photoelectric parameters of a solar cell with nanoparticles included, is two times more than that of a simple solar cell. Besides, it has been found that the efficiency of platinum nanoparticles induced solar cells is 2.15 times greater than simple solar cell efficiency. When the light incidence angle has been varied from 0 to 60 degrees, the short-circuit current has changed by 11% for simple solar cells and by 10% for solar cells with nanoparticles. Further, it has been observed that the variation of power for simple solar cells is 12.5%, while it is 10.5% for solar cells with nanoparticles. In addition, the short-circuit current of solar cells with nanoparticles has been found to be linear within a light incidence angle ranging from 0 to 60 degrees.

We report polymorph-tuned synthesis of a- and b-Bi2O3 nanowires and their single nanowire micro-Raman study. The single crystalline Bi2O3 nanowires in different phases (a and b) were selectively synthesized by adjusting the heating... more

We report polymorph-tuned synthesis of a- and b-Bi2O3 nanowires and their single nanowire micro-Raman study. The single crystalline Bi2O3 nanowires in different phases (a and b) were selectively synthesized by adjusting the heating temperature of Bi precursor in a vapor transport process.
No catalyst was employed. Furthermore, at an identical precursor evaporation temperature, a- and b- phase Bi2O3 nanowires were simultaneously synthesized along the temperature gradient at a substrate. The growth direction of a-Bi2O3 nanowires was revealed by polarized Raman single nanowire spectra. For thin b-Bi2O3 nanowire with a very small diameter, the polarized Raman single nanowire spectrum
was strongly influenced by the shape effect.

An explicit solution for long-channel surrounding-gate (SRG) MOSFETs is presented from intrinsic to heavily doped body including the effects of interface traps and quantum effects. The solution is based on the core SRGMOSFETs model of... more

An explicit solution for long-channel surrounding-gate (SRG) MOSFETs is presented from intrinsic to heavily doped body including the effects of interface traps and quantum effects. The solution is based on the core SRGMOSFETs model of Unified Charge Control Model (UCCM) for heavily doped condition. The UCCM model of highly doped SRGMOSFETs is derived to obtain the exact equivalent expression as in undoped case. Taking the advantage of the undoped explicit charge-based expression, the asymptotic limits for below threshold and above threshold have been redefined to include the effect of trap states for heavily doped case. After solving the asymptotic limits, an explicit mobile charge expression is obtained which include the trap state effects. The explicit mobile charge model shows very good agreement with respect to numerical simulation over practical terminal voltages, doping concentration, geometry effects, and trap state effects due to the fixed oxide charges and interface traps. Then, the drain current is obtained using the Pao–Sah's dual integral, which is expressed as a function of inversion charge densities at the source/drain ends. The drain current agreed well with implicit solution and numerical simulation for all regions of operation without employing any empirical parameters. In addition, the quantum effects are included based on quantum corrected model. The threshold voltage shift due to quantum confinement is incorporated to the classical model and the effective gate capacitance is recalculated due to series connected quantum capacitance. Comparison with previous explicit model has been conducted to verify the competency of the proposed model with doping concentration of 1 × 10 19 cm −3 as the proposed model has better advantages in terms of its simplicity and accuracy at higher doping concentration.

Ge growth on high-indexed Si (1110) is shown to result in the spontaneous formation of a perfectly f105g faceted one-dimensional nanoripple structure. This evolution differs from the usual Stranski- Krastanow growth mode because from... more

Ge growth on high-indexed Si (1110) is shown to result in the spontaneous formation of a perfectly
f105g faceted one-dimensional nanoripple structure. This evolution differs from the usual Stranski-
Krastanow growth mode because from initial ripple seeds a faceted Ge layer is formed that extends
down to the heterointerface. Ab initio calculations reveal that ripple formation is mainly driven by
lowering of surface energy rather than by elastic strain relief and the onset is governed by the edge energy
of the ripple facets. Wavelike ripple replication is identified as an effective kinetic pathway for the
transformation process.