Applications Of Nanowires Research Articles

Formation and Optical Characteristics of GaN:Eu/GaN Nanowires for Applications in Light-Emitting Diodes

This paper reviews our recent research about the formation and optical characteristics of GaN:Eu/GaN nanowires (NWs) by metalorganic vapor phase epitaxy for application in GaN-based red light-emitting diodes (LEDs). Two types of GaN:Eu/GaN NWs with different configurations are introduced, core–shell and axial geometries. The configuration of GaN:Eu layers on GaN core NWs can be controlled by changing the growth conditions, and affects the properties of Eu luminescence in the GaN NWs. Next, the optimization of the p-GaN growth conditions is performed to allow to form the p-GaN shell layers on the NWs with the pedestal of the NWs free from radial overgrowth, resulting in efficient electrical isolation between top and bottom part of the NWs. Then, the fabrication process of the NW LEDs towards future possible realization of flexible devices is established, including an etch-back process of the PDMS membranes to expose the top p-GaN contact layers. Finally, a proto-type of p-GaN/GaN:Eu/n-GaN NW LEDs on sapphire substrates is fabricated to characterize the device properties. Sharp red luminescence at room temperature from Eu3+ ions is observed under current injection. These results would pave the way towards the realization of flexible light-emitting devices utilizing NW structures based on compound semiconductors.

Low-Power Operating Aluminum Nitride Nanowire-Film Ultraviolet Photodetector

This work presents the fabrication and testing of a cost-effective, low power consuming, high sensitivity aluminum nitride nanowire-film-based ultraviolet photodetector. Time-dependent dynamics of photocurrent rise and decay have been investigated with varying applied bias ranging from 1 V to 20 V by periodical exposures to 254 nm ultraviolet light. The device shows stable and repeatable photocurrent cycles at low bias voltage of 1V indicating the sensitivity and low power operating capability. Furthermore, the photocurrent increases as the bias voltage increases such that the photocurrent at 20 V is approximately seventeen times larger than that of at 1 V. Despite the relatively long device length, the device reveals a quick response with a rise time of 270 ms. Moreover, the responsivity of the photodetector has been determined as 3.78 mA/W and 0.201 mA/W at 20 V and 1 V, respectively. This study demonstrates the potential of aluminum nitride nanowires for applications in next generation, low power consumption nanoscale optoelectronic devices in advanced communication, flame detection, air purification, ozone sensing, leak detection and other space monitoring.

Nylon‐11 nanowires for triboelectric energy harvesting

AbstractTriboelectric energy harvesting from ambient mechanical sources relies on motion‐generated surface charge transfer between materials with different electron affinities. In order to achieve highly efficient energy harvesting performance, choosing materials with a high surface charge density is crucial, and odd‐numbered polyamides (Nylons), such as Nylon‐11, are particularly promising due to their strong electron‐donating characteristics and the possibility to achieve dipolar alignment leading to high surface potential. The use of Nylon‐11 as a material for triboelectric energy harvesting has been rather limited due to the extreme processing conditions required for film fabrication, and the high‐voltage poling process required for dipole alignment. However, several methods to achieve “self‐poled” Nylon‐11 nanowires via facile nanoconfinement techniques have been demonstrated recently, leading to highly efficient Nylon‐11 nanowire‐based triboelectric nanogenerators. Here, we review the most recent advances in the fabrication of Nylon‐11 nanowires, with a focus on how nanoconfinement‐based fabrication methods can be used to control phase and crystallinity. These growth methods lead to self‐poled nanowires without the requirement for subsequent electrical poling, facilitating their integration into triboelectric energy harvesting devices. Strategies to fabricate Nylon‐11 nanowires for applications in triboelectric devices can be extended to other polymeric families as well.image

Abrupt elastic-to-plastic transition in pentagonal nanowires under bending.

In this study, pentagonal Ag and Au nanowires (NWs) were bent in cantilever beam configuration inside a scanning electron microscope. We demonstrated an unusual, abrupt elastic-to-plastic transition, observed as a sudden change of the NW profile from smooth arc-shaped to angled knee-like during the bending in the narrow range of bending angles. In contrast to the behavior of NWs in the tensile and three-point bending tests, where extensive elastic deformation was followed by brittle fracture, in our case, after the abrupt plastic event, the NW was still far from fracture and enabled further bending without breaking. A possible explanation is that the five-fold twinned structure prevents propagation of critical defects, leading to dislocation pile up that may lead to sudden stress release, which is observed as an abrupt plastic event. Moreover, we found that if the NWs are coated with alumina, the abrupt plastic event is not observed and the NWs can withstand severe deformation in the elastic regime without fracture. The coating may possibly prevent formation of dislocations. Mechanical durability under high and inhomogeneous strain fields is an important aspect of exploiting Ag and Au NWs in applications like waveguiding or conductive networks in flexible polymer composite materials.

Novel fabrication method for integration of template grown metallic nanocones with controllable tip diameter and apex angle

Conical metallic nanostructures, due to their geometrical and physical properties, are advantageous compared to cylindrical nanowires in applications like electron field emission cathodes. In this paper a new method for fabrication and integration of vertically aligned metallic nanocones with random distribution is reported. The nanocones are deposited electrochemically at temperatures about 60°C and lower. An area of ca. 1cm2 is covered with nanocones. The density of nanocones ranges between 6×104 and 2×106cm−2, which gives a pitch range of 23 to 7μm. With this process the growth and integration of nanocones made of different materials like e.g. Au, Ni and Cu are enabled. The tip diameter of the cones can be modified between 50 and 700nm and the base diameter between 2.5 and 7μm, i.e. apex angles between 5.9° and 16.6° can be obtained. The surface roughness of the nanocone arrays is ±0.2μm.

Structural, optical and electrical properties of gamma-rays exposed selenium nanowires

The increasing use of semiconducting nanowires in applications that require prolonged exposure to high energy photons (X-rays and gamma rays) necessitates a better understanding of the effects of irradiation on them. In this context, we synthesized selenium nanowires of 80 nm diameter using template assisted electro-deposition technique and exposed them to gamma rays using Co-60 source at Inter University Accelerator Centre, New Delhi, India. The effect of gamma irradiation on their structural, optical and electrical properties was investigated. The analysis of XRD of pre- and post- irradiated Se nanowires showed no shifting in the peak positions. However, Texture analysis demonstrates the variation in the relative intensity with changing preferred orientation at the higher doses. The optical study was done using UV–Vis spectrophotometer and was found that the optical band gap decreased with increasing gamma irradiation dose. Current–Voltage characteristics of pristine and irradiated Se nanowires also exhibit an enhancement in the current with the exposed dose. The decrease in band gap and an increase in current conduction may be attributed to the decrease in scattering of charge carriers from the grain boundaries and creation of more number of electron-hole pairs.

ChemInform Abstract: Synthesis and Characterization of Metal and Semiconductor Nanowires

AbstractReview: 160 refs.

Synthesis and Characterization of Metal and Semiconductor Nanowires

One-dimensional nanowires (NWs) have attracted considerable attention in recent years because of their novel physical properties and potential applications as interconnects in nanometre-scale electronics. NWs have potential applications in nanoscale electronics, optoelectronics, photonics, sensors, and solar cells due to their unique electrical, chemical, and optical properties. Several chemical and physical methods are commonly used to produce NWs. Among them, electrochemical synthesis and vapour-liquid-solid (VLS) methods to produce NWs have become popular among scientific workers due to a number of advantages. Synthesis of NWs using anodic alumina and polymer templates in an electrochemical cell has been described in detail as investigated in our laboratory. Characterization of metal and semiconductor NWs has been accomplished using scanning electron microscope (SEM), field emission scanning electron microscope (FESEM), high resolution transmission microscope (HRTEM), X-ray diffraction (XRD), and energy dispersive X-ray analysis (EDAX). Morphology of NWs has been revealed by SEM, structure by TEM, crystallinity by XRD and chemical composition by EDAX. I-V characteristics of copper and semiconductor NWs were recorded in-situ, as grown in pores of anodic alumina template, using Dual Source Meter (Keithley Model 4200 SCS) with platinum probes for contacts. Resonating tunneling diode (RTD) characteristics of fabricated NWs have been investigated. Bulk production of Copper NWs has been described by seed growth technique. Applications of NWs are not covered in any detail under this review. Table of Contents

Wide Bandgap Semiconductor One-Dimensional Nanostructures for Applications in Nanoelectronics and Nanosensors

Wide bandgap semiconductor ZnO, GaN and InN nanowires have displayed the ability to detect many types of gases and biological and chemical species of interest. In this review, we give some recent examples of using these nanowires for applications in pH sensing, glucose detection and hydrogen detection at ppm levels. The wide bandgap materials offer advantages in terms of sensing because of their tolerance to high temperatures, environmental stability and the fact that they are usually piezoelectric. They are also readily integrated with wireless communication circuitry for data transmission.

Combinatorial Approaches to Understanding Polytypism in III–V Nanowires

Polytypism in III-V semiconductor nanowires is a topic that has received considerable attention in recent years. Achieving a pure nanowire crystal phase requires well-controlled and advanced parameter tuning for most III-V materials. Additionally, the new and unusual phases sometimes observed may present unique material properties if they can be controllably fabricated. With the prospect of using nanowires in applications within several different fields (including electronics, photonics, and life science), theoretical models are necessary to explain experimental trends and to attain a high level of crystal phase control. At present, there is no theoretical model (or combination of models) that fully explains how and why nanowire crystal structures commonly include several different polytypes. Here we use combinatorics and interlayer interactions to include higher order polytypes (4H and 6H) with the aim to explain nanowire crystal structure beyond the well-investigated zinc blende-wurtzite polytypism. Predictions from our theoretical models compare well with experimental results.

Impact of Specifically Adsorbing Anions on the Electroless Growth of Gold Nanotubes

Electroless metal deposition on nanochannel‐containing templates is a versatile route towards metal nanotubes and nanowires if the plating reaction can be sufficiently controlled. In this study, disulfitoaurate‐formaldehyde‐based gold plating baths were modified by the addition of halides, pseudohalides, and EDTA. The introduction of specifically adsorbing anions strongly affected the heterogeneously autocatalyzed plating reaction and allowed the regulation of the reaction rate and the product morphology. The new plating baths showed enhanced stability and allowed the synthesis of homogeneous nanotubes of high aspect ratios (>150) in 30 μm thick ion track‐etched polymer templates. Depending on the reaction conditions, solid and porous structures consisting of gold nanoparticles of differing size and shape were accessible. The presented strategy offers adapted gold thin films, nanotubes, and nanowires for applications in catalysis or sensing.

Scalable alignment and transfer of nanowires based on oriented polymer nanofibers

We develop a simple and scalable method based on oriented polymer nanofiber films for theparallel assembly and transfer of nanowires at high density. Nanowires dispersed in solutionare aligned and selectively deposited at the central space of parallel nanochannelsformed by the well-oriented nanofibers as a result of evaporation-induced flow andcapillarity. A general contact printing method is used to realize the transfer of thenanowires from the donor nanofiber film to a receiver substrate. The mechanism,which involves ordered alignment of nanowires on oriented polymer nanofiberfilms, is also explored with an evaporation model of cylindrical droplets. Thesimplicity of the assembly and transfer, and the facile fabrication of large-areawell-oriented nanofiber films, make the present method promising for the application ofnanowires, especially for the disordered nanowires synthesized by solution chemistry.

Light Emission Properties of SnO<SUB>2</SUB> Nanowires for Applications in Gas Sensing

Light Emission Properties of SnO<SUB>2</SUB> Nanowires for Applications in Gas Sensing

LaB6 nanowires and their field emission properties

AbstractFor field-induced electron emission, the two factors that enable a high emission current density at low applied voltages are (a) low work function of the emitter and (b) sharpness of the emitter tip. We have developed and applied a chemical vapor deposition method to synthesize single-crystalline LaB6 nanowires for applications as point electron emitters. The crystallographic orientation of the grown nanowires can be controlled by the catalysts used in synthesis and their typical diameter is ranged from below 20 nm to over 100 nm. The nanowires’ tip is either hemispherical or flat top with rectangular cross-section depending on the catalyst being utilized. The field emission properties have also been measured from the single nanowire emitters and the results are discussed for applications as point electron sources used in high performance electron optical instruments such as the transmission and scanning electron microscopes.