Deposition Of Nanostructures Research Articles

Anodic arc discharge: Why pulsed?

Pulsed anodic arc discharge is a novel synthesis method of nanomaterials by means of low-temperature atmospheric plasma. The technique consists in periodically supplying DC power to two vertically aligned electrodes in the form of short unipolar pulses with peak currents of a few hundred Amperes in a helium atmosphere. The pulsed arc plasmas are sustained at frequencies on the order of 1 Hz with around 10% of duty cycle. It constitutes a versatile technique thanks to a series of advantages compared to continuous DC arc processes, in particular, flexibility in the experimental conditions, process stability and repeatability, better utilization of ablating anode material, lower production of macroparticles, and lower thermal loads. Such features are discussed in this article. A brief overview concerning the recent accomplishments of pulsed arc discharge on deposition of carbon nanostructures (graphene and carbon nanotubes) and few-layer flakes of molybdenum disulphide and an outlook on future applications of this method for the discovery of new materials with tailored functional properties are provided.

Atomic Layer Deposition of MoSe2 Using New Selenium Precursors

Among the emerging 2D materials, transition metal chalcogenides are particularly encouraging as alternative semiconducting graphene-like nanomaterial. Recently, 2D MoSe2 has been gaining interest due to its intriguing properties, in many ways exceeding those of the extensively studied MoS2. The deposition of 2D nanomaterials in a conformal and uniform fashion on complex-shaped nanostructures is highly appealing but only achievable by atomic layer deposition (ALD). Unfortunately, the synthesis of MoSe2 by ALD is hindered by a current substantial lack of feasible Se precursors. In this work, we synthesized a set of alkysilyl (R3Si)2Se and alkylstannyl (R3Sn)2Se compounds and studied their suitability as Se ALD precursors. Thus, ALD processes carried out using MoCl5 as Mo precursor counterpart were followed by an extensive characterization of the as deposited material. The corresponding results revealed successful deposition of MoSe2 nanostructures on substrates of different nature with dominant out-of-plane orientation. Eventually, the growth evolution of the MoSe2 during the very early ALD stage was studied and described, displaying concomitant in-plane and out-of-plane MoSe2 growth. All in all, a set of suitable Se precursors presented herein paves the way for the deposition of 2D MoSe2 with all the own ALD benefits and allow the further study of its promising properties in a wide number of applications.

Fabrication of Silver Nano-Dendrites on Optical Fibre Core by Laser-Induced Method for Surface-Enhanced Raman Scattering Applications.

In this work, we present a novel fabrication method for making the surface-enhanced Raman scattering (SERS) probe based on silver (Ag) nano-dendrites which are grown and deposited on the end of multi-mode fibre core by a simple and low-cost laser-induced technique. The morphology of the Ag-nanoparticles (AgNPs) could be controlled by the experimental conditions such as laser power, illumination time, and concentration of the reaction solution. The morphology and chemical composition of SERS fibre probes are characterized by high-resolution scanning electron microscope (HR-SEM) and Energy dispersive X-ray spectroscopy (EDX), respectively. These results confirmed how the Ag nanostructures morphology is modified as a function of illumination time of laser irradiation, and the growth and deposition of Ag nanostructures occur only in the main laser-irradiated part on the end of multi-mode fibre core. The achieved SERS-activity substrates on the fibre probes are testing with the detection of low concentration of Rhodamine 6G aqueous solutions in the range of 10-5-10-10 M. This study shows that SERS activity coupled with Ag nano-dendrites substrate on the fibre probe has the best enhancement factor of 1.93×107 for Rhodamine 6G due to the creation of many of hot-spots for amplifying Raman signals by Ag nano-dendrite structures, which is a promising candidate with low-cost SERS probe of chemical compact optical fibre sensors for direct, rapid, real-time and non-destructive detection of chemical compounds in liquid environment.

Dual Metastability in Electroless Plating: Complex Inertness Enabling the Deposition of Composition-Tunable Platinum Copper Alloy Nanostructures.

Autocatalytic deposition represents a facile, versatile, and scalable wet‐chemical tool for nanofabrication. However, the intricate component interplay in plating baths containing multiple metal species impedes alloy deposition. We resolved this challenge in the bimetallic copper‐platinum system by exploiting the kinetic stability of platinum complexes, which allows adjusting their ligand sphere and thus reactivity independently from the present copper ions in a preceding, thermally activated ligand exchange step. By using metastable PtIV precursors of varying degrees of complexation, copper‐platinum alloys of adjustable atomic ratio were plated from solutions of identical composition and concentration, but differing local coordination environment. Due to its excellent conformity and nanoscale homogeneity, the reaction is compatible with ambitious 3D substrate morphologies, as demonstrated in the template‐assisted fabrication of nanotubes with high aspect ratio. The ability to generate additional synthetic degrees of freedom by decoupling the metal complex speciation from the solution composition is of large interest for redox‐chemical synthesis techniques, such as electrodeposition or nanoparticle colloid production.

Identifying and Rationalizing the Differing Surface Reactions of Low-Energy Electrons and Ions with an Organometallic Precursor.

Surface reactions of electrons and ions with physisorbed organometallic precursors are fundamental processes in focused electron and ion beam-induced deposition (FEBID and FIBID, respectively) of metal-containing nanostructures. Markedly different surface reactions occur upon exposure of nanometer-scale films of (η5-Cp)Fe(CO)2Re(CO)5 to low-energy electrons (500 eV) compared to argon ions (860 eV). Electron-induced surface reactions are initiated by electronic excitation and fragmentation of (η5-Cp)Fe(CO)2Re(CO)5, causing half of the CO ligands to desorb. Residual CO ligands decompose under further electron irradiation. In contrast, Ar+-induced surface reactions proceed by an ion-molecule momentum/energy transfer process, causing the desorption of all CO ligands without significant ion-induced precursor desorption. This initial decomposition step is followed by ion-induced sputtering of the deposited atoms. The fundamental insights derived from this study can be used not only to rationalize the composition of deposits made by FEBID and FIBID but also to inform the choice of a charged particle deposition strategy and the design of new precursors for these emerging nanofabrication tools.

Self-supported Pt-doped ceria nanofilms directly investigated by transmission electron microscopy

In this study, we report a direct deposition of three-dimensional freestanding nanostructures of platinum-doped ceria films on holey carbon coated copper transmission electron microscopy (TEM) grid by direct liquid injection chemical vapor deposition (DLI-CVD). TEM was then directly performed on the pristine thin films, without any kind of mechanical or ion thinning. High-resolution TEM reveals that highly porous and crystallized layers were deposited over the whole membrane. The existence of platinum in the ceria grains was confirmed by Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Photoelectron Spectroscopy (XPS). Moreover, the substitution of carbon membrane by Pt-CeO2 layer was highlighted by Electron Energy Loss Spectroscopy (EELS), showing that the Pt-CeO2 nanofilms are freestanding. These results are very promising and represent an important step for performing specific nanoscale TEM analyses necessary for the study of the growth mechanism of nanofilms on substrates.

Physical vapor deposition of zinc phthalocyanine nanostructures on oxidized silicon and graphene substrates

Conventional evaporation techniques for zinc phthalocyanine (ZnPc) processing have been a preferred method for the fabrication of nanostructured films. We present a new growth methodology with independent and precise control of the growth flux and substrate temperature. This provides a consistent and well controlled growth, critical for the growth mechanism studies. ZnPc nanostructures are synthesized on single layer graphene coated silicon substrates, under a wide range of growth conditions, using this new approach. The structural features of ZnPc were investigated using Scanning Electron Microscope (SEM) and compared against previous studies of metal-phthalocyanine interactions with graphitic substrates. The observations over a wide range of evaporation conditions and substrate temperatures illustrate the ability to control film structure.

Formation of nanocraters on the surface of gold nanolayer by an impact of highly charged xenon ions

SynopsisIn this work we have systematically studied process of energy deposition and formation of nanostructures on metallic (Au nanolayer) surfaces as a result of the irradiation with slow highly charged xenon ions (HCI). Well pronounced modifications of the surfaces in form of craters were observed. We found that, in the systems considered, the kinetic energy influences the crater depth, while the potential energy affects the crater size at the surface. This finding showed that for gold nanolayers the potential energy plays important role in the nanostructures creation.

Preparation of AlN-Cu composite powders by electroless plating of controlled oxidized nitride particles to prevent degradation by hydrolysis

The present work describes the preparation of AlN-Cu composite powders by electroless plating. Initially, the hydrolysis reaction of the ceramic particles in the electroless solution was studied as a reference element for the design of a protective surface barrier that enabled the coating process, with no ceramic phase degradation. The metal source of the electrolytic bath was copper sulfate, with formaldehyde as the reducing agent, under alkaline conditions of pH 12. The microstructural characterization indicated the formation and growth of aluminum hydroxides from AlN particles, inhibiting the coating of Cu by increasing the OH− ions in the solution. As the exposure time increased, the ellipsoidal bayerite grew from AlN and transformed into prismatic particles of the thermodynamically more stable gibbsite phase. To prevent the degradation of AlN, a controlled oxidation stage was implemented to form a protective barrier of non-reactive alumina on the surface through thermal treatment in oxidizing atmospheres. An atmosphere of dry air was found to be more appropriate than pure oxygen for the formation of a continuous and dense layer of crack-free alumina on nitride surfaces, and a temperature of 1000 °C for 1 h enabled the formation of 3.9 by weight of α-Al2O3, capable of reducing the hydrolysis reaction of AlN. The process of autocatalytic deposition on the passivated particles, applied in three consecutive steps of metallization, led to AlN-Cu composite powders with 29 wt% Cu. Finally, the coated powders were treated in a hydrogen-reducing atmosphere at 400 °C to remove traces of the Al(OH)3 phase encountered, as well as to improve the adhesion of the nanostructured deposit of the cauliflower-like structure to the AlN surfaces, obtaining AlN-Cu composite powders suitable for the preparation of metal/ceramic composites.

Durable Antimicrobial Behaviour from Silver-Graphene Coated Medical Textile Composites.

Silver nanoparticle (AgNP) and AgNP/reduced graphene oxide (rGO) nanocomposite impregnated medical grade polyviscose textile pads were formed using a facile, surface-mediated wet chemical solution-dipping process, without further annealing. Surfaces were sequentially treated in situ with a sodium borohydride (NaBH4) reducing agent, prior to formation, deposition, and fixation of Ag nanostructures and/or rGO nanosheets throughout porous non-woven (i.e., randomly interwoven) fibrous scaffolds. There was no need for stabilising agent use. The surface morphology of the treated fabrics and the reaction mechanism were characterised by Fourier transform infrared (FTIR) spectra, ultraviolet-visible (UV–Vis) absorption spectra, X-ray diffraction (XRD), Raman spectroscopy, dynamic light scattering (DLS) energy-dispersive X-ray analysis (EDS), and scanning electron microscopic (SEM). XRD and EDS confirmed the presence of pure-phase metallic silver. Variation of reducing agent concentration allowed control over characteristic plasmon absorption of AgNP while SEM imaging, EDS, and DLS confirmed the presence of and dispersion of Ag particles, with smaller agglomerates existing with concurrent rGO use, which also coincided with enhanced AgNP loading. The composites demonstrated potent antimicrobial activity against the clinically relevant gram-negative Escherichia coli (a key causative bacterial agent of healthcare-associated infections; HAIs). The best antibacterial rate achieved for treated substrates was 100% with only a slight decrease (to 90.1%) after 12 equivalent laundering cycles of standard washing. Investigation of silver ion release behaviours through inductively coupled plasmon optical emission spectroscopy (ICP-OES) and laundering durability tests showed that AgNP adhesion was aided by the presence of the rGO host matrix allowing for robust immobilisation of silver nanostructures with relatively high stability, which offered a rapid, convenient, scalable route to conformal NP–decorated and nanocomposite soft matter coatings.

Deposition and patterning of gold nanostructures on various wettable and nonwettable patterned surfaces

Suspensions comprises of gold nanostructures deposited on a number of alternating wettable silicon dioxide (SiO2) and nonwettable perfluorodecyltrichlorosilane (PFDTS) patterned surfaces via droplet evaporation technique. On such surfaces during evaporation of aqueous phase, three-phased contact line of a droplet deposit nanoparticles preferentially on the wettable set of stripes and consequently leads to nanoparticles patterning over the substrate. The presence of the nonwettable stripes on both sides of the wettable stripe on such patterned substrates will push the liquid towards the wettable stripe. Such liquid drive will induce hydrodynamic confinement effect. This hydrodynamic confinement will produce nanoparticle patterns that will merely decorate wettable stripes with gold nanorod deposits. Aligned arrays of gold nanorods are observed near the interfacial boundaries. Ribbon-like arrays of face-to-face aligned nanorods are observed in some locations within the deposits. In case of citrate-stabilized gold nanospheres (diameter∼10 nm), bonding sites for nanospheres on the wettable stripes are provided by the self-assembled monolayers of 3-triethoxysilylpropylamine (APTES). The presence of APTES will facilitate gold nanoparticles deposition (monolayer) on the wettable stripes whereas nonwettable stripes demonstrated agglomerated and mobilized bunches of nanoparticles. As such nanoparticle clusters are unstable on the PFDTS surface, hence can be removed by air blowing mechanism. The air rushing across the substrate removes nearly all nanoparticles settled over the nonwettable stripes whereas nanoparticle arrangement on the wettable region remains unaltered.

THE EFFECT OF ANNEALING TEMPERATURE ON OPTICAL AND PHOTOLUMINESCENCE PROPERTIES OF LiNbO3

This paper concerns deposition of nano and micro structures of Lithium Niobate (LiNbO3) on a quartz substrate using sol–gel method. The nanostructure was deposited based on spin coating technique with speed of 3000[Formula: see text]rpm for 30[Formula: see text]s. Samples were exposed for different annealing temperature ranges from 100∘C to 600∘C. The optical properties and the morphological results of the grown films have been investigated using the scanning electron microscope (SEM), atomic force microscopy (AFM), optical study through UV–Visible and Photoluminescence (PL). The results showed that good transmission and bandgap properties can be obtained as the annealing temperature increases. In contrast, the higher annealing temperature results in reduction of the refractive index value, and the grains are regularly distributed within the film as a result of increasing the annealing temperature. This comes from the growing effect of packs density as a result of oxidation process during heating process.

Controlled Electroless Deposition of Noble Metals on Silicon Substrates Using Self-Assembled Monolayers as Molecular Resists To Generate Nanopatterned Surfaces for Electronics and Plasmonics

Electroless deposition of noble metals on silicon has applications in a wide range of fields including electronic circuitry, metal plating industry, lithography, and other fabrication techniques. In addition, studies using self-assembled monolayers (SAMs) as resists for electroless deposition for controlled deposition have significant potential for aiding advancement in the fields of nanoelectronics, sensing applications, and fundamental studies. Herein, we discuss the development of appropriate plating solutions for controlled deposition of metallic gold and silver on Si(111) surfaces in the presence of an organic silane monolayer acting as a resist film for directed metal deposition to produce metal-monolayer hybrid surfaces while investigating microscopic plating trends. For this, plating solutions were optimized to deposit metal on bare silicon surfaces while avoiding deposition on the SAM protected areas. Trends in the electroless deposition of gold and silver on a Si(111) surface as a function of concentration of metal ions, NH4F, citric acid, sodium citrate, polyvinylpyrrolidone (PVP), and deposition time have been monitored under ambient conditions. The resulting surfaces were characterized using atomic force microscopy (AFM), and the stability of plating solutions was investigated by UV–vis spectroscopy. For both gold and silver, we observed an increase in metal deposition when the concentration of NH4F, citric acid, and deposition time increased. The addition of PVP and the pH of the solution were also shown to have a significant effect on the metal deposition. The octadecyltrichlorosilane (OTS) SAM films act as effective nanoscale resists when the NH4F concentration is reduced from typical plating conditions. In particular, NH4F concentrations from 0.02 to 0.50 M and metal ions concentrations from 0.001 to 0.020 M were found to allow deposition of metal nanostructures on a bare Si surface while preserving OTS protected areas.

Copper Electrodeposition on Textile for Wearable Electronics

Two main tasks in fabricating a circuit is to pattern the interconnections and soldering elements to the patterned conductive traces. Using copper growth electrodeposition assisted by hydrogen evolution as a technique for integration of electronic elements and circuits in fabrics and flexible substrates particularly useful for soldering electronic components, representing an advantage over conventional methods and providing a high quality of the deposits requiring relatively inexpensive equipment. This method has shown high rate of deposition and formation of nanostructures, expected to anchor to the fibers of a fabric for enhanced stability of the structure. Moreover, the technique has proven to be reliable for soldering electronic components at room temperature. A copper pattern can be achieved over a MWCNTs coating by the copper growth deposition in the electrochemical cell after electrolysis is reached in the cell with the aqueous solution of Cu2+ and H2SO4. Cu2+ions interact with hydrogen allowing the formation of the reaction product by the application of voltages above 1.0V. The electrodeposition parameters and the quality of the copper being deposited will be analyzed to find the optimum conditions for fast copper deposition and adhesion to the fabric structure and also will be tested for soldering simple electronic elements and it will be studied to be more resilient during laundry.

Potentiostatic deposition of CoNi2Se4 nanostructures on nickel foam as efficient battery-type electrodes for supercapacitors

Bimetallic CoNi2Se4 nanostructures on nickel-foam substrates were fabricated by a potentiostatic deposition method by adjusting the deposition solution pH, and used as electrode materials in battery-type supercapacitors. The electrodeposition solution pH had an important role in the fabrication of the desirable CoNi2Se4 nanostructures. At a deposition solution pH of 2.0, the synthesized product contained CoNi2Se4 nanoparticles. In contrast, a partially converted flake-like morphology was obtained at pH = 2.5. The appropriate flake-like morphology was formed by increasing the deposition solution pH to 3.0. The robust flake-like structure facilitated the electron transport during redox reactions, providing an excellent electrochemical behavior in terms of specific capacity, rate capability, and cyclic stability. A battery-type supercapacitor based on the flake-like CoNi2Se4 structure exhibited a maximum specific capacity of 632.5 C g−1 at a current density of 1 A g−1 and excellent rate performance (capacity retention of 91%) in the range of 1 to 40 A g−1. The material retained 83.31% of its initial capacity after 3000 cycles of charging/discharging at a current density of 40 A g−1, which suggests a high long-term cycling stability. The excellent electrochemical performance of the CoNi2Se4 electrode material make it very promising for application in supercapacitors.

Hydrothermal deposition of CoS nanostructures and its multifunctional applications in supercapattery and water electrolyzer

The development of sustainable energy conversion and storage systems is on demand to ease the energy needs and restrict environmental pollution. Here, we account a unique multifunctional flake-like CoS deposited over the flexible carbon cloth (CoS@CC) by a facile hydrothermal technique. The single-phase hexagonal structured CoS@CC with high crystallinity was identified through the XRD analysis. The morphological feature portrays the uniform distribution of flake-like CoS over carbon cloth. The electrocatalytic properties of the prepared flake-like CoS (CoS@CC) suggests improved electroactivity of requiring minimal overpotentials of 280 mV (OER) and 264 mV (HER) to accomplish a pre-eminent current density of 20 mA cm−2. In addition, a lab-scale water splitting system was projected to achieve a current density of 10 mA cm−2 with a low cell voltage of 1.65 V. In view to driving the fabricated water splitting system, a flexible (CoS@CC||rGO) supercapattery was fabricated to deliver an improved specific energy of 38 Wh kg−1 at a superior specific power of 533 W kg−1. Therefore, the prepared CoS@CC electrode with improved flexibility, useful catalytic activity, expressive kinetics, and resilient strength serves as a multifunctional material for prospective energy conversion and storage systems.

Facile development of highly sensitive femtomolar electrochemical DNA biosensor using gold nanoneedle-modified electrode

In this paper, a simple one-step electrochemical method was employed for the deposition of gold nanostructures. Different morphologies (Au-nanorods and Au-nanoneedles) were obtained using different concentrations of gold chloride (HAuCl4·3H2O) solution. The gold nanostructure-modified surface was used for the fabrication of DNA biosensor, which was characterized by cyclic voltammetry and differential pulse voltammetry. The DNA immobilization and hybridization on Au-nanorods and Au-nanoneedles showed a detection limit of 10 fM and 0.2 fM, respectively, with wide dynamic range of 0.2 fM to 10 nM. The Au-nanoneedle electrode showed improved detection limit, which is fifty times lower than that of the Au-nanorods. The electrochemical DNA biosensor showed a good selectivity and sensitivity towards the detection of target DNA. The enhancement in response of DNA biosensor would be an exciting addition in clinical diagnosis due to an improved detection limit.

Coffee ring effect assisted improved S. aureus screening on a physically restrained gold nanoflower enriched SERS substrate

Proactive water pathogen identification process holds significance in view of increasing bioterrorism prospects, quantification of virulence properties and water supply regulation for human welfare. Strikingly, pathogen concentration is rather low in water bodies to be identified using conventional methods and usually involves three typical steps: 1) concentration 2) purification and 3) characterization and assay. Surface enhanced Raman scattering (SERS) analysis on other hand could easily surpass these steps to give a rather robust identification owing to its exceptionally high specificity and sensing abilities. In this article we use SERS as a diagnostic tool to identify low concentrations of noxious pathogens from water, using a two level confinement that results in a superlative SERS analytical assay, capable of analyte identification down to single molecule level. Unlike the regular dip coat process, we restrict the nanostructure deposition only to a very small area of the larger substrate, by restricting its application volume. In this way, we limit our data processing time, increase our probability of target interaction and also reduce nanostructure/analyte sample quantities for analysis. To enhance the signal intensities further, we use natural three phase pinning or the coffee ring effect to pre-concentrate the analytes on our spatially confined nanostructure pocket, allowing maximal deposition at the edges and subsequently higher signal intensities. The methodology was employed to measure the presence of S. aureus and R6 G in spiked drinking water. LOD achieved for R6 G and S. aureus is 10−12 M and 103 CFU/ml respectively. The increasing signal intensities share a linear relationship with analyte concentration. The acquired signals were reproducible and non-degenerate, overcoming the drawback of irregular data patterns associated with conventional metal nanostructure based SERS systems. Estimated RSD value for physical confinement and coffee ring effect measured was 11.6% and 8.37% respectively. This simple, low cost, robust and reproducible method can be useful for increasing the sensitivity of SERS based detection devices with capability to be developed into a micro total analysis system (μTAS).

Lossy mode resonance sensors based on lateral light incidence in nanocoated planar waveguides

The deposition of an indium oxide (In2O3) thin film on conventional planar waveguides (a coverslip and a glass slide) allows generating lossy mode resonances (LMR) by lateral incidence of light on the waveguide and by registering the optical spectrum in a spectrometer. This novel sensing system becomes an alternative to optical fibre, the substrate where LMR-based sensors have been developed so far, since it is easier to handle and more robust. An additional advantage is that cost effective waveguides, such as slides or coverslips, can be used in a platform that resembles surface plasmon resonance-based sensors in the Kretschmann configuration but without the need for a coupling prism and with the advantage of being able to generate TE and TM LMR resonances with metallic oxide or polymer thin films. The results are corroborated with simulations, which provide in-depth understanding of the phenomena involved in the sensing system. As a proof-of-concept for the optical platform, two refractometers were developed, one with low sensitivity and for a wide range of refractive indices, and the other with higher sensitivity but for a narrower refractive index range. The sensors presented here open up the path for the development of LMR-based chemical sensors, environmental sensors, biosensors, or even the generation of other optical phenomena with the deposition of multilayer structures, gratings or nanostructures, which is much easier in a planar waveguide than in an optical fibre.

Discharge regimes and emission characteristics of capacitively coupled radio frequency argon plasma with a square wave input

This work presents a computational and experimental investigation of capacitively coupled radio frequency argon plasma in a roll-to-roll chemical vapor deposition system for carbon nanostructure growth. The system operates at moderate pressures (less than 30 mbar) with an 80 kHz square wave voltage input. The computational model aids the understanding of plasma properties and α–γ transition parameters which strongly influence the nanostructure deposition characteristics in the system. A 1D plasma model is developed to characterize the effects of input voltage, gas pressure, frequency, and waveform on the plasma properties. A hybrid mode which displays the characteristics of both α and γ discharges is found to exist for the low cycle frequency 80 kHz square wave voltage input due to the high frequency harmonics associated with a square waveform. The modeled gas temperatures are 22.5% higher than the experimentally measured values due to the presence of molecular species in the experiments. Collision radiative modeling is performed to predict the argon emission intensity in the discharge gap. The results are found to lie within 16% of the optical emission spectroscopy measurements with better agreement at the center of the discharge, where the measurement uncertainty is low and the emission by ions is not significant.