Deposition Of Nanowires Research Articles

Morphology and Magnetic Properties of Ni Nanowires in Thin Film Anodic Alumina Templates

The features of the morphology and magnetic properties of Ni nanowire arrays have been studied. Aluminum oxide matrices are used as a template for electrolytic deposition of nanowires. The matrices are obtained by anodizing the aluminum films with a thickness of 2 μm that are formed on glass substrates by high frequency ion sputtering. Electrochemical deposition of the metal is carried out using direct and alternating currents. Morphology and microstructure studies show that the nanowire arrays are polycrystalline and have a branched dendritic structure due to the morphological features of aluminum oxide matrices. A relationship between the magnetization reversal patterns and the modes of electrodeposition of Ni nanowire arrays is established. The process of magnetization reversal of an array of this kind of structures is simulated.

Tunable Hydrogen-Related Defects in ZnO Nanowires Using Oxygen Plasma Treatment by Ion Energy Adjustment.

The chemical bath deposition (CBD) process enables the deposition of ZnO nanowires (NWs) on various substrates with customizable morphology. However, the hydrogen-rich CBD environment introduces numerous hydrogen-related defects, unintentionally doping the ZnO NWs and increasing their electrical conductivity. The oxygen-based plasma treatment can modify the nature and amount of these defects, potentially tailoring the ZnO NW properties for specific applications. This study examines the impact of the average ion energy on the formation of oxygen vacancies (VO) and hydrogen-related defects in ZnO NWs exposed to low-pressure oxygen plasma. Using X-ray photoelectron spectroscopy (XPS), 5 K cathodoluminescence (5K CL), and Raman spectroscopy, a comprehensive understanding of the effect of the oxygen ion energy on the formation of defects and defect complexes was established. A series of associative and dissociative reactions indicated that controlling plasma process parameters, particularly ion energy, is crucial. The XPS data suggested that increasing the ion energy could enhance Fermi level pinning by increasing the amount of VO and favoring the hydroxyl group adsorption, expanding the depletion region of charge carriers. The 5K CL and Raman spectroscopy further demonstrated the potential to adjust the ZnO NW physical properties by varying the oxygen ion energy, affecting various donor- and acceptor-type defect complexes. This study highlights the ability to tune the ZnO NW properties at low temperature by modifying plasma process parameters, offering new possibilities for a wide variety of nanoscale engineering devices fabricated on flexible and/or transparent substrates.

SYNTHESIS AND STUDY OF OPTICAL, ELECTRICAL PROPERTIES OF TIN DIOXIDE NANOWIRES IN A SiO<sub>2</sub>/Si TRACK TEMPLATE

This work presents a study of the structural, optical and electrical characteristics of tin dioxide (SnO2) nanowires obtained by chemical deposition (CD) into a SiO2/Si track template (template synthesis). Latent tracks in the SiO2 layer were created by irradiation with swift heavy ions (SHI) of Xe at an energy of 200 MeV with a fluence of Ф = 108 cm−2 and subsequent etching in a 4% aqueous solution of hydrofluoric acid (HF). The chosen CD method is widely used for the deposition of semiconductor oxide nanowires in SiO2 nanopores. The CD method is cost-effective because it does not require special equipment for deposition of nanowires. To carry out deposition, a solution of a coordination compound of a metal and a reducing agent is used. To analyze the filling of pores after the CD process, the surface morphology of the samples was studied using a Zeiss Crossbeam 540 scanning microscope. The crystallographic structure of SnO2/SiO2/Si nanostructures with SnO2 nanopore filling was studied by X-ray diffraction. X-ray diffraction analysis (XRD) is carried out on a Rigaku SmartLab X-ray diffractometer. As a result, a SnO2-NW/SiO2/Si nanoheterostructure with an orthorhombic crystal structure of SnO2 nanowires was obtained. Photoluminescence (PL) spectra were measured upon excitation with light at a wavelength of 240 nm using a CM2203 spectrofluorimeter (Solar). Gaussian decomposition of the photoluminescence spectrum of SnO2-NW/SiO2/Si structures showed that they have low intensity, which is mainly due to the presence of defects such as oxygen vacancies, interstitial tin or tin with damaged bonds. Electrical characterization studies were performed using a VersaStat 3 potentiostat (Ametek). Measurement of the current-voltage characteristic showed that the resulting SnO2-NW/SiO2/Si nanoheterostructure contains arrays of p-n junctions.

Strain-Sensor-In-Pixel Technology for Resolution-Sustainable Stretchable Displays.

One of the limitations of stretchable displays is the severe degradation of resolution or the decrease in the number of pixels per unit area when stretched. Hence, we suggest a strain-sensor-in-pixel (S-SIP) system through the adoption of hidden pixels that are activated only during the stretch mode for maintaining the density of on-state pixels. For the S-SIP system, the gate and source electrodes of InGaZnO thin-film transistors (TFTs) in an existing pixel are connected to a resistive strain sensor through the facile and selective deposition of silver nanowires (AgNWs) via electrohydrodynamic-jet-printing. With this approach, the strain sensor integrated TFT functions as a strain-triggered switch, which responds only to stretching along the designated axes by finely tuning the orientation and cycles of AgNW printing. The strain sensor-integrated TFT remains in an off-state when unstretched and switches to an on-state when stretched, exhibiting a large negative gauge factor of -1.1 × 1010 and a superior mechanical stability enduring 6000 cycles, which enables the efficient structure to operate hidden pixels without requiring additional signal processing. Furthermore, the stable operation of the S-SIP in a 5 × 5-pixel array is demonstrated via circuit simulation, implying the outstanding applicability and process compatibility to the conventional active-matrix display backplanes.

One-pot hydrothermal film deposition and characterization of 1T-MoS2 nanowires for photodetection

One-pot hydrothermal film deposition and characterization of 1T-MoS2 nanowires for photodetection

Development of a wearable surface enhanced Raman scattering sensor chip based on silver nanowires for rapid detection of urea, lactate and pH in sweat

A wearable sweat sensor chip based on surface-enhanced Raman spectroscopy (SERS) is here presented. The plasmonic core of the chip, obtained by deposition of silver nanowires on a polytetrafluoroethylene (PTFE) porous membrane, permits the direct and label-free detection of urea and lactate at physiologic concentrations in combination with the pH measurement in the range between 5 and 9. Once integrated with commercial biocompatible and adhesive tape layers, the as produced SERS-active chip provides a low-cost, flexible and wearable sensing device for rapid and reliable human sweat analysis. The chip was finally tested on real sweat samples to estimate lactate and urea during medium-intense exertions.

Deposition of Transparent Ag Nanowires‐Based Top Electrode for the Development of Double‐Side Green Light Hybrid Photodetector

Herein, various silver nanowires (AgNWs) deposition techniques, i.e., spin coating, Mayer rod coating, and spray coating are used to fabricate ZnO/P3HT‐based double‐side hybrid photodetectors and their photoresponse for 520 nm green light has been compared. The electrodes are coated over the polyethylene terephthalate sheet separately and laminated over the indium tin oxide (ITO)/ZnO/P3HT. Mayer rod‐coated electrodes are found to have a sheet resistance (Rsh) of 24 Ω Sq.−1 and a light transmission of 91%. Additionally, spin‐ and spray‐coated AgNW electrodes exhibit Rsh of 20 and 23 Ω Sq.−1, respectively, along with 80% and 85% transparencies. As the device consists of transparent electrodes on both sides, it can detect light from both the top and bottom sides. Mayer rod‐coated AgNW electrode‐based device has produced better photosensitivity of 1500 (for ITO side illumination) and 630 (for AgNWs side illumination) at λ = 525 nm. Further, the device has demonstrated the responsivity of 124 mAW−1 and specific detectivity of 3 × 1011 Jones.

Electrohydrodynamic Jet Morphology Modulation for Highly Spatially Controllable Piezoelectric Nanowire Deposition

Electrohydrodynamic Jet Morphology Modulation for Highly Spatially Controllable Piezoelectric Nanowire Deposition

Atomic Layer Deposition and Strain Analysis of Epitaxial GaN-ZnO Core-Shell Nanowires.

We demonstrate the epitaxial coating of GaN NWs with an epitaxial ZnO shell by atomic layer deposition at 300 °C. Scanning transmission electron microscopy proves a sharp and defect-free coherent interface. The strain in the core-shell structure due to the lattice mismatch and different thermal expansion coefficients of GaN and ZnO was analyzed using 4D-STEM strain mapping and Raman spectroscopy and compared to theoretical calculations. The results highlight the outstanding advantages of epitaxial shell growth using atomic layer deposition, e.g., conformal coating and precise thickness control.

Construction of Nb2CTx/α-MnO2 composites by electrostatic self-assembly for controllable impedance matching and enhanced electromagnetic absorption

Nb2CTx/α-MnO2 composites have been constructed by the deposition of α-MnO2 nanowires on the surface of the layered Nb2CTx matrix through an electrostatic self-assembly strategy. The increase of α-MnO2 content can lead to an improvement of permittivity and a shift of the reflection peak towards low frequency at a fixed thickness. Theory analysis speculates that the synergistic effect of lattice defect and electron hopping of Mn4+-O-Mn3+ chains in α-MnO2 nanowires as well as heterogeneous interfaces between Nb2CTx and α-MnO2 are predominant accounts for the enhancement of permittivity. The effective complementary of impedance matching and microwave attenuation can be responsible for the displacement of the reflection peak towards low frequency and a wide-frequency absorption. Accordingly, Nb2CTx/α-MnO2 composites exhibit an optimal reflection loss of -24.7 dB and an absorption bandwidth of 5 GHz at a thin matching thickness of 1.8 mm, which are better than those of most Nb2CTx-based absorbents.

Nib-Assisted Coaxial Electrohydrodynamic Jet Printing for Nanowires Deposition.

This paper presents the concrete design of nanowires under the precise size and morphology that play a crucial role in the practical operation of the micro/nano devices. A straightforward and operative method termed as nib-assistance coaxial electrohydrodynamic (CEHD) printing technology was proposed. It extracts the essence of a nib-assistance electric field intensity to enhance and lessen the internal fluid reflux of the CEHD jet. The experiments were performed to add microparticles into the inner liquid to indicate the liquid flow consistency within the coaxial jet. The reflux in the coaxial jet was observed for the first time in experiments. The nanowires with a minimum size of 70 nm were printed under optimum experimental conditions. The nanopatterns contained aligned nanowires structures with diameters much smaller than the inner diameter of nozzle, relying on the coaxial nib-assisted technique. The printed results revealed that the nib-assisted CEHD printing technique offers a certain level high quality for application of NEMS system.

Effect of composition, electrolyte pH, annealing temperature and electrodeposition waveform on the magnetic properties of Co-Cu nanowire alloys

Arrays of Co0.2Cux, with 0<x<0.1, nanowires (NWs) have been synthesized. CoCu NWs have been grown into the AAO templates by ac electrodeposition. The anodic aluminum oxide template (AAO) were synthesized by a two-step anodization process of pure Al foils in sulfuric acid. The effect of small addition of Cu to Co NWs by varying the concentrations of Cu+2 ions in the electrolyte, as well as the effect of annealing on the magnetic properties of NWs was investigated. Eventually, the effect of changing waveforms applied to nanowire deposition was studied. The results showed that the coercivity of cobalt NWs decreased by adding copper impurity as a non-magnetic material from 1337 Oe to 660 Oe. By annealing of the alloy NWs up to 450 °C, the coercivity increases from 1140 Oe value for pure Co NWs up to 1541 Oe for CoCu NWs due to the removal of structural stresses of the nanowire.

Synthesis and Deposition of Silver Nanowires on Porous Silicon as an Ultraviolet Light Photodetector.

The applications of silver nanowires (AgNWs) are clearly relevant to their purity and morphology. Therefore, the synthesis parameters should be precisely adjusted in order to obtain AgNWs with a high aspect ratio. Consequently, controlling the reaction time versus the reaction temperature of the AgNWs is crucial to synthesize AgNWs with a high crystallinity and is important in fabricating optoelectronic devices. In this work, we tracked the morphological alterations of AgNWs during the growth process in order to determine the optimal reaction time and temperature. Thus, here, the UV-Vis absorption spectra were used to investigate how the reaction time varies with the temperature. The reaction was conducted at five different temperatures, 140-180 °C. As a result, an equation was developed to describe the relationship between them and to calculate the reaction time at any given reaction temperature. It was observed that the average diameter of the NWs was temperature-dependent and had a minimum value of 23 nm at a reaction temperature of 150 °C. A significant purification technique was conducted for the final product at a reaction temperature of 150 °C with two different speeds in the centrifuge to remove the heavy and light by-products. Based on these qualities, a AgNWs-based porous Si (AgNWs/P-Si) device was fabricated, and current-time pulsing was achieved using an ultra-violet (UV) irradiation of a 375 nm wavelength at four bias voltages of 1 V, 2 V, 3 V, and 4 V. We obtained a high level of sensitivity and detectivity with the values of 2247.49% and 2.89 × 1012 Jones, respectively. The photocurrent increased from the μA range in the P-Si to the mA range in the AgNWs/P-Si photodetector due to the featured surface plasmon resonance of the AgNWs compared to the other metals.

Multifunctional polyimide-based femtosecond laser micro/nanostructured films with triple Janus properties.

Flexible multifunctional composite films in which opposing surfaces have two or more distinct physical properties are highly applicable for wearable electronic devices, electrical power systems and biomedical engineering. However, fabrication of such "Janus" films can be time consuming, complex or economically not feasible. In this work, Janus polyimide (PI) films were prepared by femtosecond laser direct writing technology, which generated a honeycomb porous structure (HPS) on one side and a lawn-like structure (LLS) on the other. Deposition of silver nanowires (AGNWs) by drop coating on the LLS side (AGNWs@LLS) resulted in a film in which each face possessed highly distinct triple properties. The HPS side was superhydrophobic with a water contact angle (WCA) of ∼153.3° and electrically non-conductive, while the AGNWs@LLS side was superhydrophilic (WCA ∼7.8°) and highly conductive (∼3.8 Ω). Moreover, the AGNWs@LLS face showed ultra-low thermal radiation performance, almost reaching saturation. On a heating table at ∼100 °C, the temperature of the AGNWs@LLS side remained at ∼44.5 °C, while the HPS side exhibited a temperature of ∼93.9 °C. This "triple Janus film" and lasing techniques developed might be useful for designing new materials for the integration and miniaturization of multifunctional electronic equipment.

Influence of natural convection on the electrodeposition of copper nanowires in anodic aluminium oxide templates

Templated electrodeposition is a versatile method for preparing metal nanostructures. Among the various parameters of this process, the effect of convection on the deposition process is less explored. The present work is devoted to the experimental and theoretical study of the influence of natural convection near nanoporous anodic aluminium oxide templates on the deposition of nanowires. Electrochemical deposition of copper nanowires was carried out with vertical templates parallel to the gravitational acceleration at various overpotentials. A model of nanowire electrodeposition was developed based on the Navier‒Stokes and diffusion equations. The length profiles of the nanowires, experimentally measured using scanning electron microscopy, were compared with the results of the numerical simulation. The simulation results were also compared with current-time transients recorded during metal electrodeposition into nanopores. In addition, an analytical expression has been proposed to describe the evolution of the deposition current density into nanopores under natural convection conditions.

Breathable, Flexible, Transparent, Hydrophobic, and Biotic Sustainable Electrodes for Heating and Biopotential Signal Measurement Applications

Pressure to reduce the global amount of e‐waste has increased in recent years. The optimal use of natural resources is a demanding area especially due to the overabundance of the use of resources and challenges with after‐life disposal. Herein, an easy method is developed to fabricate an improved version of leaf skeleton‐based biodegradable, transparent, flexible, and hydrophobic electrodes. A fractal‐like rubber leaf skeleton is used as the substrate, physical vapor deposited Au interlayer to promote adhesion, and uniform deposition of overlayer silver nanowires. The fabricated surfaces present a high level of electrical stability, optical transparency, hydrophobicity, and robust mechanical properties. The prepared electrodes demonstrate a comparable level of optical transmittance to the virgin leaf skeleton. The mechanical sturdiness of the electrodes is verified by 1k bending cycles. To demonstrate the functionality of these hybrid biotic conductive network (HBCN) electrodes, their performance is evaluated as flexible transparent heating elements and as biosignal measurement electrodes. The heater can reach a temperature of 140 °C with only 2.5 V in ≈5 s and Ag nanowire loading of ≈160 μg cm−2. Likewise, electrocardiogram (ECG) and electromyogram (EMG) signals are successfully obtained from the electrodes without using any electrode gel or other electrolytes.

Scanning Electrochemical Cell Microscopy: A Tool for Nanoscopic Deposition of Light-Driven Photocatalysts

Single and multi-barrel nanopipettes and nanopipette-based scanning electrochemical probe microscopy techniques like scanning electrochemical cell microscopy (SECCM) have gained significant attention as tools for localized, maskless, three-dimensional surface modifications [1,2]. The nanometer-sized orifices of nanopipettes allow delivering molecules to solution inducing concentration-confined electrodepositions. Also, electroless nanoscale depositions like the fountain pen technique [3] can be achieved by this technique.In this study, we present the deposition of various cobaloxime-based earth-abundant Co catalysts for light-driven hydrogen evolution reaction (HER) [4]. Arrays of different cobalt(III) complexes were deposited via SECCM and investigated in respect with their HER activity using scanning electrochemical microscopy (SECM) in combination of Pd-microsensors [5] for in situ hydrogen (H2) measurements under illumination. In addition, AFM studies revealed possible degradation of the commercially available neutral benchmark complex [Co(dmgH)2(py)Cl] in these studies. First results will also be presented in respect with the deposition of nanowires via co-deposition of HER catalyst and Ruthenium photosensitizer. First spatially resolved photocatalytic studies at such nanowires, which are characterized by high surface area, will be presented. Also, the influence of the substrate will also be discussed.

Enhanced Photocatalytic Activity and Photoluminescence of ZnO Nano-Wires Coupled with Aluminum Nanostructures.

In this study, we fabricated a hybrid plasmonic/semiconductor material by combining the chemical bath deposition of zinc oxide nanowires (ZnONWs) with the physical vapor deposition of aluminum nanostructures (AlNSs) under controlled temperature and atmosphere. The morphological and the optical properties of the ZnONWs/AlNSs hybrid material fabricated at different temperatures (250, 350, and 450 °C) and thicknesses (5, 7, and 9 nm) of Al layers were investigated. By adjusting the deposition and annealing parameters, it was possible to tune the size distribution of the AlNSs. The resonant coupling between the plasmonic AlNSs and ZnONWs leads to an enhanced photoluminescence response. The photocatalytic activity was studied through photodegradation under UV-light irradiation of methylene blue (MB) adsorbed at the surface of ZnO. The MB photodegradation experiment reveals that the ZnONWs covered with 7 nm aluminum film and annealed at 450 °C exhibit the highest degradation efficiency. The comparison between ZnONws and ZnONws/AlNSs shows a photoluminescence enhancement factor of 1.7 and an increase in the kinetics constant of photodegradation with a factor of 4.

Implementing the Reactor Geometry in the Modeling of Chemical Bath Deposition of ZnO Nanowires.

The formation of nanowires by chemical bath deposition is of great interest for a wide variety of optoelectronic, piezoelectric, and sensing devices, from which the theoretical description of their elongation process has emerged as a critical issue. Despite its strong influence on the nanowire growth kinetics, reactor size has typically not been taken into account in the theoretical modeling developed so far. We report a new theoretical description of the axial growth rate of nanowires in dynamic conditions based on the solution of Fick’s diffusion equations, implementing a sealed reactor of finite height as a varying parameter. The theoretical model is applied in various chemical bath deposition conditions in the case of the growth of ZnO nanowires, from which the influence of the reactor height is investigated and compared to experimental data. In particular, it is found that the use of reactor heights smaller than 2 cm significantly decreases the ZnO nanowires’ axial growth rate in typical experimental conditions due to the faster depletion of reactants. The present approach is further used predictively, showing its high potential for the design of batch reactors for a wide variety of chemical precursors and semiconductor materials in applied research and industrial production.

Bio-Inspired Hierarchical Micro/Nanostructured Surfaces for Superhydrophobic and Anti-Ice Applications.

We report a scalable and cost-effective fabrication approach for constructing bio-inspired micro/nanostructured surfaces. It involves silicon microstructure etching using a deep reactive ion etch (DRIE) method, nanowires deposition via glancing angle deposition (GLAD) process, and fluorocarbon thin film deposition. Compared with the smooth, microstructured, and nanostructured surfaces, the hierarchical micro/nanostructured surfaces obtained via this method showed the highest water contact angle of ∼161° and a low sliding angle of <10°. It also offered long ice delay times of 2313 s and 1658 s at −5°C and −10°C respectively, more than 10 times longer than smooth surfaces indicating excellent anti-icing properties and offering promising applications in low-temperature environments. These analyses further proved that the surface structures have a significant influence on surface wettability and anti-icing behavior. Hence, the GLAD process which is versatile and cost-effective offers the freedom of constructing nanostructures on top of microstructures to achieve the required objective in the fabrication of micro/nanostructured surfaces when compared to other fabrication techniques.