0000000001307224
AUTHOR
Donats Erts
Institute of Chemical Physics consists of Nanomaterials Lab
The main research directions - investigation of properties and possible applications of nanostructured materials such as nanowires, nanotubes, nanoparticles.
Catalyst-free vapour-solid technique for deposition of Bi2Te3 and Bi2Se3 nanowires/nanobelts with topological insulator properties.
We present a simple two-stage vapour–solid synthesis method for the growth of bismuth chalcogenide (Bi2Te3, Bi2Se3) topological insulator nanowires/nanobelts by using Bi2Se3 or Bi2Te3 powders as source materials. During the first stage of the synthesis process nanoplateteles, serving as “catalysts” for further nanowire/nanobelt growth, are formed. At a second stage of the synthesis, the introduction of a N2 flow at 35 Torr pressure in the chamber induces the formation of free standing nanowires/nanobelts. The synthesised nanostructures demonstrate a layered single-crystalline structure and Bi : Se and Bi : Te ratios 40 : 60 at% for both Bi2Se3 and Bi2Te3 nanowires/nanobelts. The presence of…
Devices based on semiconductor nanowires
Recently, nanoelectromechanical systems (NEMS) have attracted much attention due to their unique properties and possible applications that differ greatly from those of microelectromechanical systems. NEMS operating frequencies may achieve giga- and terahertz levels and their power consumption and heat capacity is extremely low. Moreover, integration levels may reach 1012 devices per cm−2. In this review, we present techniques for integrating semiconductor materials in NEMS. In particular, we examine fabrication, structure, properties and potential applications of two main classes of NEMS, namely, resonators and switches.
High-Density Plasmonic Nanoparticle Arrays Deposited on Nanoporous Anodic Alumina Templates for Optical Sensor Applications
This study demonstrates a new, robust, and accessible deposition technique of metal nanoparticle arrays (NPAs), which uses nanoporous anodic alumina (NAA) as a template for capillary force-assisted convective colloid (40, 60, and 80 nm diameter Au) assembly. The NPA density and nanoparticle size can be independently tuned by the anodization conditions and colloid synthesis protocols. This enables production of non-touching variable-density NPAs with controllable gaps in the 20&ndash
An AC-assisted single-nanowire electromechanical switch
A unique two-source controlled nanoelectromechanical switch has been assembled from individual, single-clamped Ge nanowires. The switching behaviour was achieved by superimposing the control signals of specific frequencies to the electrostatic potential of the output terminals, eliminating the need for an additional gate electrode. Using an in situ manipulation technique inside a scanning electron microscope, we demonstrate that the pull-out force required to overcome adhesion at the contact can be significantly reduced by exciting mechanical resonant modes within the nanowire.
Characterization of thermoelectric and thermogravimetric properties of conductive PEDOT:PSS films blended with SWCNTs and PVA
Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) was blended with polyvinyl alcohol (PVA) and single-walled carbon nanotube (SWCNT) filler to form composites with thermoelectric properties. Studied samples were obtained by drop coating and solution casting methods. Thermoelectric measurements of PEDOT:PSS demonstrated that the addition of 5 wt. % SWCNTs increased the Seebeck coefficient value from 8.0 μV/K to 23.6 μV/K, while in the case of PEDOT:PSS/PVA blended with 5 wt. % SWCNT Seebeck coefficient value of 20.3 μV/K was achieved. Thermogravimetric analysis showed slight SWCNT effect on thermal stability of the investigated systems.
Optical properties of ultrathin Al2O3/ZnO nanolaminates
Abstract Because of their high resistance against ultraviolet and high energy particles, ultrathin amorphous nanolaminates can be very attractive for aerospace application. Here we report on the optical and structural properties of ultrathin Al2O3/ZnO nanolaminates deposited by Atomic Layer Deposition. Structural properties of nanolaminates were studied by GIXRD and AFM. Optical characterization was performed by transmittance, spectroscopic ellipsometry and photoluminescence (PL) spectroscopy. Regression analysis of ellipsometric spectra has shown that absorption peak decreases and blue shifted with the decrease of bilayer thickness in the stack. On the basis of the analysis of structural a…
Sensing properties of assembled Bi2S3nanowire arrays
Bismuth sulfide (Bi2S3) nanowires were grown in porous aluminium oxide template and a selective chemical etching was applied to transfer the nanowires to a solution. Well aligned nanowire arrays were assembled on pre-patterned silicon substrates employing dielectrophoresis. Electron beam lithography was used to connect aligned individual nanowires to the common macroelectrode. In order to evaluate the conductometric sensing performance of the Bi2S3 nanowires, current–voltage characteristics were measured at different relative humidity (RH) levels (5–80%) / argon medium. The response of the Bi2S3 nanowires depending of RH is found to be considerably different from those reported for other ty…
Tuning Optical Properties of Al 2 O 3 /ZnO Nanolaminates Synthesized by Atomic Layer Deposition
Nanolaminates are of great interest for their unique properties such as high dielectric constants and advanced mechanical, electrical, and optical properties. Here we report on the tuning of optical and structural properties of Al2O3/ZnO nanolaminates designed by atomic layer deposition (ALD). Structural properties of nanolaminates were studied by SEM, GIXRD, and AFM. Optical characterization was performed by transmittance and photoluminescence (PL) spectroscopy. Complex study of monolayer properties was performed by ellipsometry. Optical constants for Al2O3 and ZnO monolayer were calculated. The band gap of ZnO single layers and the excitonic PL peak position were shifted to the UV region …
Deformation behavior and interfacial sliding in carbon/copper nanocomposite films deposited by high power DC magnetron sputtering
Abstract Amorphous carbon–copper nanocomposite films with a carbon content from 7 to 40 at.% have been deposited onto steel, silicon and glass substrates using a high power (> 60 W/cm 2 ) and high-rate DC magnetron sputtering technique. XRD, Raman spectroscopy and TEM results confirm that the deposited films consist of copper nanograins (size
Growth mechanisms and related thermoelectric properties of innovative hybrid networks fabricated by direct deposition of Bi2Se3 and Sb2Te3 on multiwalled carbon nanotubes
Abstract Flexible thermoelectric generators are an emerging trend in the field of waste heat conversion, as well as wearable and autonomous devices. However, the energy conversion efficiency of the state-of-the-art flexible thermoelectric devices is too low for their wide application and commercialization. In this work, n- and p-type multiwalled carbon nanotube (MWCNT)-thermoelectric material hybrid networks that may become a promising building block for the fabrication of flexible thermoelectric devices are presented. The hybrid networks were fabricated by direct deposition of thermoelectric material (Bi2Se3, Sb2Te3) on the MWCNT networks using physical vapor deposition technique. Growth m…
Probing of nanocontacts inside a transmission electron microscope
In the past twenty years, powerful tools such as atomic force microscopy have made it possible to accurately investigate the phenomena of friction and wear, down to the nanometer scale. Readers of this book will become familiar with the concepts and techniques of nanotribology, explained by an international team of scientists and engineers, actively involved and with long experience in this field. Edited by two pioneers in the field, 'Fundamentals of Frictions and Wear at the Nanoscale' is suitable both as first introduction to this fascinating subject, and also as a reference for researchers wishing to improve their knowledge of nanotribology and to keep up with the latest results in this …
Ultrathin Anodic Aluminum Oxide Membranes for Production of Dense Sub-20 nm Nanoparticle Arrays
We present a systematic study of membrane structure (pore diameter and arrangement) in anodized aluminum oxide (AAO) layers obtained by anodization voltages 8-20 V in sulfuric and 15-40 V in oxalic acid electrolyte solutions. Anodization of bulk aluminum in sulfuric acid at 10 V potential was found to be optimal for production or ultrathin freestanding membranes with pore diameter in sub-20 nm range. The developed process with slow electrochemical reaction results in AAO membranes with thickness below 70 nm. The minimum required time for formation of continuous AAO membrane was determined and influence of electrolyte concentration on pore diameter in membrane after barrier layer removal ana…
Structure and Doping Determined Thermoelectric Properties of Bi2Se3Thin Films Deposited by Vapour–Solid Technique
In this work, a simple catalyst-free vapour-solid deposition method was applied for controlled deposition of two types (planar and disordered) of continuous Bi 2 Se 3 nanostructured thin films on different (fused quartz/glass, mica, graphene) substrates. Characterisation of electron transport (type, concentration and mobility of the main charge carriers) and thermoelectric properties (Seebeck coefficient and power factor) showed that proposed in this work deposition method allows to obtain Bi 2 Se 3 thin films with power factor comparable and even higher than reported for the Bi 2 Se 3 thin films grown by molecular beam epitaxy technique. Power factor of the best obtained thin films can be …
Bulk-free topological insulator Bi 2 Se 3 nanoribbons with magnetotransport signatures of Dirac surface states
Many applications for topological insulators (TIs) as well as new phenomena require devices with reduced dimensions. While much progress has been made to realize thin films of TIs with low bulk carrier density, nanostructures have not yet been reported with similar properties, despite the fact that size confinement should help reduce contributions from bulk carriers. Here we demonstrate that Bi2Se3 nanoribbons, grown by a simple catalyst-free physical-vapour deposition, have inherently low bulk carrier densities, and can be further made bulk-free by size confinement, thus revealing the high mobility topological surface states. Magneto transport and Hall conductance measurements, in single n…
Dielectrophoretic alignment and electrical characterization of CuO nanowire-based systems
Abstract Dielectrophoresis is used to assemble nanowires between metallic electrodes to form scalable functional interconnects. The dielectrophoresis parameters are investigated for semiconductor copper oxide (CuO) nanowires that are desirable for energy conversion and storage, gas sensors and nanoelectromechanical systems. Experimental yields of multiple- and single-nanowire interconnects are explored at dielectrophoresis frequencies from 500 Hz to 500 kHz. The electrical properties of nanowire-electrode physical contact interfaces formed by dielectrophoresis, metal deposition, and dry mechanical transfer are investigated. The electrical transport mechanism in these interconnects is determ…
Photoluminescence immunosensor based on bovine leukemia virus proteins immobilized on the ZnO nanorods
Bovine leukaemia virus (BLV) proteins gp51, which are serving as antigens for specific antibodies against BLV proteins (anti-gp51), were applied as biological recognition part in the design of immunosensor devoted for the determination of anti-gp51. The efficiency of the immobilization of BLV proteins gp51 on ZnO nanorod (ZnO- NR) modified glass (ZnO-NR/glass) surface was evaluated. The formation of antigen-antibody complex on the ZnO/glass modified by the BLV proteins gp51 (gp51/ZnO-NR/glass) was investigated by the determination of changes in ZnO photoluminescence. The applicability of gp51/ZnO-NR/glass in the design of photoluminescence based immunosensor was evaluated. Bovine serum albu…
High-Mobility Ambipolar Magnetotransport in Topological Insulator Bi2Se3 Nanoribbons
Nanoribbons of topological insulators (TIs) have been suggested for a variety of applications exploiting the properties of the topologically protected surface Dirac states. In these proposals it is crucial to achieve a high tunability of the Fermi energy, through the Dirac point while preserving a high mobility of the involved carriers. Tunable transport in TI nanoribbons has been achieved by chemical doping of the materials so to reduce the bulk carriers' concentration, however at the expense of the mobility of the surface Dirac electrons, which is substantially reduced. Here we study bare ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ nanoribbons transferred on a variety of oxide substrates and dem…
Fabrication and Characterization of Double- and Single-Clamped CuO Nanowire Based Nanoelectromechanical Switches
Electrostatically actuated nanoelectromechanical (NEM) switches hold promise for operation with sharply defined ON/OFF states, high ON/OFF current ratio, low OFF state power consumption, and a compact design. The present challenge for the development of nanoelectromechanical system (NEMS) technology is fabrication of single nanowire based NEM switches. In this work, we demonstrate the first application of CuO nanowires as NEM switch active elements. We develop bottom-up and top-down approaches for NEM switch fabrication, such as CuO nanowire synthesis, lithography, etching, dielectrophoretic alignment of nanowires on electrodes, and nanomanipulations for building devices that are suitable f…
Visible Photoluminescence of Variable-Length Zinc Oxide Nanorods Embedded in Porous Anodic Alumina Template for Biosensor Applications
Zinc oxide (ZnO) and porous anodic aluminum oxide (PAAO) are technologically important materials, rich with features that are of interest in optical applications, for example, in light-emitting and sensing devices. Here, we present synthesis method of aligned ZnO nanorods (NR) with 40 nm diameter and variable length in 150 to 500 nm range obtained by atomic layer deposition (ALD) of ZnO in pores of continuously variable thickness PAAO. The relative intensity of yellow (1.99 eV), green (2.35 eV), and blue (2.82 eV) photoluminescence (PL) components originating from the different types of defects, varied with non-monotonic dependency on the composite film thickness with a Fabry–Pérot like mod…
Cryogenic nanoelectromechanical switch enabled by Bi2Se3 nanoribbons
Abstract Nanoelectromechanical (NEM) switches are potential candidates for memory and logic devices for low standby-current and harsh environment applications. Cryogenic operation of these devices would allow to use them, e.g., in space probes and in conjunction with quantum computers. Herein, it is demonstrated that cryogenic application requirements such as good flexibility and conductivity are satisfied by using Bi2Se3 nanoribbons as active elements in NEM switches. Experimental proof of principle NEM switching at temperatures as low as 5 K is achieved in volatile and non-volatile reversible regimes, exhibiting distinct ON and OFF states, backed by theoretical modelling. The results open…
Evolution of microstructure and related optical properties of ZnO grown by atomic layer deposition.
A study of transmittance and photoluminescence spectra on the growth of oxygen-rich ultra-thin ZnO films prepared by atomic layer deposition is reported. The structural transition from an amorphous to a polycrystalline state is observed upon increasing the thickness. The unusual behavior of the energy gap with thickness reflected by optical properties is attributed to the improvement of the crystalline structure resulting from a decreasing concentration of point defects at the growth of grains. The spectra of UV and visible photoluminescence emissions correspond to transitions near the band-edge and defect-related transitions. Additional emissions were observed from band-tail states near th…
Surface Lattice Resonances in Self-Assembled Arrays of Monodisperse Ag Cuboctahedra
Plasmonic metal nanoparticles arranged in periodic arrays can generate surface lattice plasmon resonances (SLRs) with high Q-factors. These collective resonances are interesting because the associated electromagnetic field is delocalized throughout the plane of the array, enabling applications such as biosensing and nanolasing. In most cases such periodic nanostructures are created via top-down nanofabrication processes. Here we describe a capillary-force-assisted particle assembly method (CAPA) to assemble monodisperse single-crystal colloidal Ag cuboctahedra into nearly defect-free >1 cm2 hexagonal lattices. These arrays are large enough to be measured with conventional ultraviolet-visibl…
Longitudinal spin-relaxation in nitrogen-vacancy centers in electron irradiated diamond
We present systematic measurements of longitudinal relaxation rates ($1/T_1$) of spin polarization in the ground state of the nitrogen-vacancy (NV$^-$) color center in synthetic diamond as a function of NV$^-$ concentration and magnetic field $B$. NV$^-$ centers were created by irradiating a Type 1b single-crystal diamond along the [100] axis with 200 keV electrons from a transmission electron microscope with varying doses to achieve spots of different NV$^-$ center concentrations. Values of ($1/T_1$) were measured for each spot as a function of $B$.
Surface structure promoted high-yield growth and magnetotransport properties of Bi2Se3 nanoribbons
AbstractIn the present work, a catalyst-free physical vapour deposition method is used to synthesize high yield of Bi2Se3 nanoribbons. By replacing standard glass or quartz substrates with aluminium covered with ultrathin porous anodized aluminium oxide (AAO), the number of synthesized nanoribbons per unit area can be increased by 20–100 times. The mechanisms of formation and yield of the nanoribbons synthesized on AAO substrates having different arrangement and size of pores are analysed and discussed. It is shown that the yield and average length of the nanoribbons can base tuned by adjustment of the synthesis parameters. Analysis of magnetotransport measurements for the individual Bi2Se3…
Application of Room Temperature Photoluminescence From ZnO Nanorods for Salmonella Detection
ZnO nanorods grown by gaseous-disperse synthesis are confirmed by XRD analysis to have the wurtzite crystal structure. The obtained crystallites, as found from SEM studies, are 57 +/- 9 nm in diameter and 470 +/- 30 nm long on the average. Two emission bands of photoluminescence from ZnO nanorods observed at room temperature are centered at 376 and 520 nm. A biosensitive layer is prepared by immobilization of anti-Salmonella antibodies from liquid solutions on the ZnO surface. Immobilization of the biosensitive layer onto ZnO nanorods is found to increase the intensity of PL. After further reaction with Salmonella antigens (Ags), the PL intensity is found to decrease proportional to Ag conc…
The influence of localized plasmons on the optical properties of Au/ZnO nanostructures
Optical and structural experiments have been carried out on Si/ZnO thin films modified with ultra-thin gold layers of different thicknesses. ZnO was produced via Atomic Layer Deposition (ALD) and Au via Physical Vapor Deposition (sputtering). The structural properties of nanostructures were studied by XRD and AFM. Optical characterization was performed by absorbance, photoluminescence (PL) and spectroscopic ellipsometry (SE). A transition from cluster-to-thin films with the increase of Au thickness has been revealed from an analysis of optical and structural parameters. The analysis of optical features of the system has shown that slight changes of the localized plasmon absorption peaks in …
Studies of host-guest thin films of corona-poled betaine-type polar molecules by kelvin probe technique and atomic force microscopy
In this work betaine-type molecules were investigated. As a result of the asymmetry of charge distribution, molecules possess in the ground state a considerable permanent dipole moment. The decay of surface potential of poled polymer films is dependent at least on two relaxation processes. The influence of glass transition of PMMA on thermal dependence of the surface potential is shown. The transition temperature, where no changes of the surface potential appeared, is related to glass transition temperature of the host-guest system. The topography of the film surface was obtained by AFM.
Improved Crystalline Structure and Enhanced Photoluminescence of ZnO Nanolayers in Bi2Se3/ZnO Heterostructures
The Bi2Se3/ZnO heterostructure is a new combination of high- and low-band-gap nanomaterials that can be implemented for optoelectronic devices. The influence of the Bi2Se3 substrate on crystallizat...
Studies of the initial oxidation of cobalt in alkaline solutions using scanning electrochemical microscope
Studies of the initial oxidation of cobalt in alkaline solutions using scanning electrochemical microscope
Photoconductivity of Germanium Nanowire Arrays Incorporated in Anodic Aluminum Oxide
Photoconductivity of germanium nanowire arrays of 50 and 100 nm diameter incorporated into Anodic Aluminum Oxide (AAO) membranes illuminated with visible light is investigated. Photocurrent response to excitation radiation with time constants faster than 10−4 s were governed by absorption of incident light by nanowires, while photokinetics with time constants of the order of 10−3 s originates from the photoluminescence of the AAO matrix. Possible applications of nanowire arrays inside AAO as photoresistors are discussed.
Nanoindentation response analysis of Cu-rich carbon–copper composite films deposited by PVD technique
Abstract The micromechanical properties of sputter deposited amorphous carbon–copper (a-C/Cu) composite films with different carbon content (6.8–19.8 at.%) were investigated. Atomic force and electron microscopy studies confirmed that the a-C/Cu films have a two-phase microstructure of amorphous sp 2 /sp 3 -bonded carbon as a composite matrix with embedded copper nanocrystallites encapsulated in a graphene shell. Load–displacement curves obtained in nanoindentation experiments followed Meyer's law with the exponent varying slightly within the interval 2.0–2.2 depending on the penetration depth and carbon content. The reverse indentation size effect was observed which was most likely the res…
Probing the magnetic properties of cobalt–germanium nanocable arrays
We report the synthesis of high density arrays of coaxial nanocables, consisting of germanium nanowires surrounded by cobalt nanotube sheaths, within anodic aluminium oxide membranes. The nanocable arrays were prepared using a supercritical fluid inclusion process, whereby the cobalt nanotubes were first deposited on the pore walls of the nanoporous membranes and subsequently filled with germanium to form coaxial nanocables. The composition and structure of the metal–semiconductor nanostructures was investigated by electron microscopy, energy dispersive X-ray mapping and X-ray diffraction at high angles. The magnetic properties of the co-axial nanocables were probed using a superconducting …
Role of Nanoelectromechanical Switching in the Operation of Nanostructured Bi2Se3 Interlayers between Conductive Electrodes
We demonstrate a simple low-cost method of preparation of layered devices for opto- and thermoelectric applications. The devices consist of a functional Bi2Se3 layer of randomly oriented nanoplates and flexible nanobelts enclosed between two flat indium tin oxide (ITO) electrodes. The number of functional interconnections between the ITO electrodes and correspondingly the efficiency of the device can be increased by gradual nanoelectromechanical (NEM) switching of flexible individual Bi2Se3 nanobelts in the circuit. NEM switching is achieved through applying an external voltage to the device. For the first time, we investigate in situ NEM switching and breakdown parameters of Bi2Se3 nanobel…
Correlation analysis of vibration modes in physical vapour deposited Bi 2 Se 3 thin films probed by the Raman mapping technique
In this work, the Raman spectroscopy mapping technique is used for the analysis of mechanical strain in Bi2Se3 thin films of various (3-400 nm) thicknesses synthesized by physical vapour deposition on amorphous quartz and single-layer graphene substrates. The evaluation of strain effects is based on the correlation analysis of in-plane (E2g) and out-of-plane (A21g) Raman mode positions. For Bi2Se3 films deposited on quartz, experimental datapoints are scattered along the line with a slope of similar to 0.85, related to the distribution of hydrostatic strain. In contrast to quartz/Bi2Se3 samples, for graphene/Bi2Se3 heterostructures with the same thicknesses, an additional negative slope of …
Self-assembly of C60 fullerene molecules in the hexane–xylene solvent system
The behavior of self-assembly of C60 molecules in solutions of C60/hexane/xylene were studied by the methods of refractometry, ultraviolet–visible spectroscopy and dynamic light scattering (DLS). I...
Force interactions and adhesion of gold contacts using a combined atomic force microscope and transmission electron microscope
Force interactions and adhesion of gold contacts using a combined atomic force microscope and transmission electron microscope
High-Density Arrays of Germanium Nanowire Photoresistors
Here we present for the first time a study of the photoresistive properties and dynamics of ordered, high-density arrays of germanium nanowire photoresistors. Germanium is a wellknown semiconducting material with an indirect bandgap, Eg, of approximately 0.66 eV (temperature T = 300 K) and has been widely used for the fabrication of photodetectors, radiation detectors, charged particle and photon tracking devices, far-infrared photoresistors, and numerous other devices. During the last few years there has also been increasing interest in the use of nanostructures (quantum dots and wires) of both germanium and silicon as materials for potential applications in sensors, nanophotonics, and nan…
Tuning of ZnO 1D nanostructures by atomic layer deposition and electrospinning for optical gas sensor applications
We explored for the first time the ability of a three-dimensional polyacrylonitrile/ZnO material—prepared by a combination of electrospinning and atomic layer deposition (ALD) as a new material with a large surface area—to enhance the performance of optical sensors for volatile organic compound (VOC) detection. The photoluminescence (PL) peak intensity of these one-dimensional nanostructures has been enhanced by a factor of 2000 compared to a flat Si substrate. In addition, a phase transition of the ZnO ALD coating from amorphous to crystalline has been observed due to the properties of a polyacrylonitrile nanofiber template: surface strain, roughness, and an increased number of nucleation …
Young’s modulus and indirect morphological analysis of Bi2Se3nanoribbons by resonance measurements
An electrostatically induced resonance behaviour of individual topological insulator Bi2Se3 nanoribbons grown by a catalyst free vapour-solid synthesis was studied in situ by scanning electron microscopy. It was demonstrated that the relation between the resonant frequencies of vibrations in orthogonal planes can be applied to distinguish the nanoribbons with rectangular cross-sections from the nanoribbons having step-like morphology (terraces). The average Young's modulus of the Bi2Se3 nanoribbons with rectangular cross-sections was found to be 44 ± 4 GPa.
Deposition of Cu Nanoparticles on the Surface of Metallic Aluminum
Deposition of Cu particles by electrolysis at constant electrode potential and by internal electrolysis methods was investigated. The composition of deposited material was confirmed by optical and scanning electron microscope methods. Combination of electrolysis at constant electrode potential with internal electrolysis method was found most effective for fabrication of nanoparticle arrays. Single crystalline Cu particles are fabricated by internal electrolysis, while polycrystalline ones obtained by combined chronopotentiometric and internal electrolysis methods. The formation mechanism of Cu nanoparticles is described.
Electrochemically etched sharp aluminium probes with nanoporous aluminium oxide coatings: demonstration of addressed DNA delivery
Electrochemical etching of metal wires is widely used to fabricate sharp probes for use in scanning tunnelling microscopy. In this work an electrochemical fabrication method for sharp aluminium probes coated with nanoporous anodised aluminium oxide (AAO) layer is described. The method presented here involves simultaneous anodisation and etching of aluminium wires. The probe apex radius as well as the nanopore length and diameter depend on the etching mode, which could be direct current (DC), alternating current (AC), or pulsed voltage mode (PVM). The probes, coated with a nanoporous AAO layer, were used to demonstrate addressed DNA delivery.
Polymerization and Damage of C60 Single Crystals under Low Fluency Laser Irradiation
Photo-induced hardening, substructure formation and damage of C 60 single crystals under the 632.8 nm He-Ne laser irradiation in air at a power density of 1.47 mW/mm 2 was investigated by microhardness and AFM methods. Photo-induced formation of the dislocation substructure and crystallographically oriented crack patterns on the (111) face due to lattice contraction on polymerization were observed. Two phototransformed states: soft (400-450 MPa) and hard (650-1000 MPa) are found to appear under laser-irradiation. Hard fullerite is created in the subsurface layer < 1 μm at the saturation stage of phototransformation. It softens to 400-450 MPa at 340 K and reverts to non-polymerized state at …
Conductive films of ordered nanowire arrays
peer-reviewed High-density, ordered arrays of germanium nanowires have been synthesised within the pores of mesoporous thin films (MTFs) and anodized aluminium oxide (AAO) matrices using a supercritical fluid solution-phase inclusion technique. Conductive atomic force microscopy (C-AFM) was utilised to study the electrical properties of the nanowires within these arrays. Nearly all of the semiconductor nanowires contained within the AAO substrates were found to be conducting. Additionally, each individual nanowire within the substrate possessed similar electrical properties demonstrating that the nanowires are continuous and reproducible within each pore. C-AFM was also able to probe the co…
Fabrication of an extremely cheap poly(3,4-ethylenedioxythiophene) modified pencil lead electrode for effective hydroquinone sensing
Hydroquinone (HQ) is one of the major deleterious metabolites of benzene in the human body, which has been implicated to cause various human diseases. In order to fabricate a feasible sensor for the accurate detection of HQ, we attempted to electrochemically modify a piece of common 2B pencil lead (PL) with the conductive poly(3,4-ethylenedioxythiophene) or PEDOT film to construct a PEDOT/PL electrode. We then examined the performance of PEDOT/PL in the detection of hydroquinone with different voltammetry methods. Our results have demonstrated that PEDOT film was able to dramatically enhance the electrochemical response of pencil lead electrode to hydroquinone and exhibited a good linear co…
Photoconductive properties of Bi2S3nanowires
The photoconductive properties of Bi2S3 nanowires synthesized inside anodized alumina (AAO) membrane have been characterized as a function of illuminating photon energy between the wavelengths of 500 to 900 nm and at constant illumination intensity of 1–4 μW·cm−2. Photoconductivity spectra, photocurrent values, photocurrent onset/decay times of individual Bi2S3 nanowires liberated from the AAO membrane were determined and compared with those of arrays of as-produced Bi2S3 nanowires templated inside pores of AAO membrane. The alumina membrane was found to significantly influence the photoconductive properties of the AAO-hosted Bi2S3 nanowires, when compared to liberated from the AAO membrane…
Porous silicon based photoluminescence immunosensor for rapid and highly-sensitive detection of Ochratoxin A.
A rapid and low cost photoluminescence (PL) immunosensor for the determination of low concentrations of Ochratoxin A (OTA) has been developed. This immunosensor was based on porous silicon (PSi) and modified by antibodies against OTA (anti-OTA). PSi layer was fabricated by metal-assisted chemical etching (MACE) procedure. Main structural parameters (pore size, layer thickness, morphology and nanograins size) and composition of PSi were investigated by means of X-Ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy. PL-spectroscopy of PSi was performed at room temperature and showed a wide emission band centered at 680 ± 20nm. Protein A was covalently immobilized …
Synthesis and characterization of highly ordered cobalt-magnetite nanocable arrays.
Magnetically tunable, high-density arrays of coaxial nanocables within anodic aluminum oxide (AAO) membranes have been synthesized. The nanocables consist of magnetite nanowires surrounded by cobalt nanotube sheaths and cobalt nanowires surrounded by magnetite nanotube sheaths. These materials are a combination of separate hard (Co) and soft (Fe3O4) magnetic materials in a single nanocable structure. The combination of two or more magnetic materials in such a radial structure is seen as a very powerful tool for the future fabrication of magnetoresistive, spin-valve and ultrafast spin-injection devices with nonplanar geometries. The nanocable arrays were prepared using a supercritical-fluid …
Determination of Young’s modulus of Sb2S3 nanowires by in situ resonance and bending methods
In this study we address the mechanical properties of Sb2S3 nanowires and determine their Young’s modulus using in situ electric-field-induced mechanical resonance and static bending tests on individual Sb2S3 nanowires with cross-sectional areas ranging from 1.1·104 nm2 to 7.8·104 nm2. Mutually orthogonal resonances are observed and their origin explained by asymmetric cross section of nanowires. The results obtained from the two methods are consistent and show that nanowires exhibit Young’s moduli comparable to the value for macroscopic material. An increasing trend of measured values of Young’s modulus is observed for smaller thickness samples.
Extra tension at electrode-nanowire adhesive contacts in nano-electromechanical devices
Abstract We report a strong tangential component of the reaction force at electrode to nanowire adhesive contact which was previously established using electrostatic attraction. The reaction force tangential component absolute value was found to be comparable to or even bigger than the corresponding normal component. This effect is important for understanding of the mechanics of nano-electromechanical devices. Both the experiment and the corresponding theory are presented. Fitting of the obtained analytical solutions to experimental data was used to measure the reaction force acting at the contact for several nanowire-electrode configurations.
Two-terminal nanoelectromechanical devices based on germanium nanowires.
A two-terminal bistable device, having both ON and OFF regimes, has been demonstrated with Ge nanowires using an in situ TEM-STM technique. The function of the device is based on delicately balancing electrostatic, elastic, and adhesion forces between the nanowires and the contacts, which can be controlled by the applied voltage. The operation and failure conditions of the bistable device were investigated, i.e. the influence of nanowire diameter, the surface oxide layer on the nanowires and the current density. During ON/OFF cycles the Ge nanowires were observed to be more stable than carbon nanotubes, working at similar conditions, due to the higher mechanical stability of the nanowires. …
Electric and elastic properties of conductive polymeric nanocomposites on macro- and nanoscales
Abstract In the past several years, the macroscopic electric and elastic properties of conductive polymeric composites have been studied from the viewpoint of such applications as thermistors and pressure sensors. In particular, we studied carbon black (CB) polymeric nanocomposites on macro- and nanoscales, using polyisoprene as the composite matrix. The filler component was an extra conductive carbon black (PRINTEX XE2, DEGUSSA) with a primary particle diameter of about 30 nm. A very strong reversible tensoresistive effect of electric resistance dependence on uniaxial tension deformation was observed in composites with the 10 carbon black mass parts added to 100 mass parts of polyisoprene.…
Thickness-dependent properties of ultrathin bismuth and antimony chalcogenide films formed by physical vapor deposition and their application in thermoelectric generators
This work was supported by the European Regional Development Fund (ERDF) project No 1.1.1.1/16/A/257. J. A. acknowledges the ERDF project No. 1.1.1.2/1/16/037. Institute of Solid State Physics, University of Latvia, Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017 TeamingPhase2 under grant agreement No. 739508, project CAMART2 . The raw/processed data required to reproduce these findings cannot be shared at this time as the data also form a part of an ongoing study.
Topological insulator nanoribbon Josephson junctions: Evidence for size effects in transport properties
We have used Bi$_2$Se$_3$ nanoribbons, grown by catalyst-free Physical Vapor Deposition to fabricate high quality Josephson junctions with Al superconducting electrodes. In our devices we observe a pronounced reduction of the Josephson critical current density $J_c$ by reducing the width of the junction, which in our case corresponds to the width of the nanoribbon. Because the topological surface states extend over the entire circumference of the nanoribbon, the superconducting transport associated to them is carried by modes on both the top and bottom surfaces of the nanoribbon. We show that the $J_c$ reduction as a function of the nanoribbons width can be accounted for by assuming that on…
Porous Aluminium Oxide Coating for the Development of Spectroscopic Ellipsometry Based Biosensor: Evaluation of Human Serum Albumin Adsorption
An electrochemically synthesised porous anodic aluminium oxide (pAAO) layer has been analysed by means of spectroscopic ellipsometry. The determined thickness of the formed pAAO layer obtained from spectroscopic ellipsometry measurements and modelling was 322.75 ±
High-Yield Growth and Tunable Morphology of Bi2Se3 Nanoribbons Synthesized on Thermally Dewetted Au
The yield and morphology (length, width, thickness) of stoichiometric Bi2Se3 nanoribbons grown by physical vapor deposition is studied as a function of the diameters and areal number density of the Au catalyst nanoparticles of mean diameters 8–150 nm formed by dewetting Au layers of thicknesses 1.5–16 nm. The highest yield of the Bi2Se3 nanoribbons is reached when synthesized on dewetted 3 nm thick Au layer (mean diameter of Au nanoparticles ~10 nm) and exceeds the nanoribbon yield obtained in catalyst-free synthesis by almost 50 times. The mean lengths and thicknesses of the Bi2Se3 nanoribbons are directly proportional to the mean diameters of Au catalyst nanoparticles. In contrast, the me…
Investigating the mechanical properties of GeSn nanowires.
Germanium tin (GeSn) has been proposed as a promising material for electronic and optical applications due to the formation of a direct band-gap at a Sn content >7 at%. Furthermore, the ability to manipulate the properties of GeSn at the nanoscale will further permit the realisation of advanced mechanical devices. Here we report for the first time the mechanical properties of GeSn nanowires (7.1-9.7 at% Sn) and assess their suitability as nanoelectromechanical (NEM) switches. Electron microscopy analysis showed the nanowires to be single crystalline, with surfaces covered by a thin native amorphous oxide layer. Mechanical resonance and bending tests at different boundary conditions were use…
Optical properties of thin metal films with nanohole arrays on porous alumina–aluminum structures
A multilayer system is formed by the deposition of a 10–35 nm thin Au or Ag film with 18–25 nm diameter holes on 75–280 nm thick layers of porous anodized aluminum oxide (AAO) supported by a bulk sheet of aluminum. We present a detailed study of system parameters, which influence the optical response, including the porosity, metal layer thickness and crystallographic orientation of the Al substrate. The spectral properties are mainly governed by the interference of the reflections from the Al substrate and the thin metal film separated by the AAO layer. An enhanced plasmonic attenuation component near 650 nm for the Au films with holes can be observed when the interferometric anti-reflectio…
Space charge limited current mechanism in Bi2S3 nanowires
We report on the charge transport properties of individual Bi2S3 nanowires grown within the pores of anodized aluminum oxide templates. The mean pore diameter was 80 nm. Space charge limited current is the dominating conduction mechanism at temperatures below 160 K. Characteristic parameters of nanowires, such as trap concentration and trap characteristic energy, were estimated from current-voltage characteristics at several temperatures.
Application of Ge Nanowire for Two-Input Bistable Nanoelectromechanical Switch
Recently, several research groups presented bistable two-terminal nanoelectromechanical switches based on individual single-clamped active element. All presented devices had one input electrode. Similar devices having two or more input electrodes have not been yet investigated. In this work we present the two-input bistable controlled nanoelectromechanical switch based on an individual single-clamped Ge nanowire. The switch is realised using in-situ SEM technique and operating due to balancing of electrostatic, adhesion and elastic forces. The operation conditions of the device are investigated and presented. The advantages and drawbacks of the device are discussed. DOI: http://dx.doi.org/1…
Fabrication of a biocompatible and continuous glucose biosensor with the poly(3,4-ethylenedioxythiophene) modified electrode
Abstract In this study, we have explored the potentiality of using GOx/AuNP/PEDOT(BSA)/Pt electrode as an implantable, long-lasting, and sensitive glucose biosensor. We have examined the performance of the electrode for glucose calibration with three electrochemical measurements, such as cyclic voltammetry, linear sweep voltammetry, as well as chronoamperometry, which all exhibited strong linear correlation between resulting signal and glucose concentration. In comparison, linear sweep voltammetry gave the best linear sensitivity, whose average was about 3.124 µA/mM/cm2 within a wide glucose concentration range from 0.416 to 50 mM. Meanwhile, the stability of the electrode was confirmed by …
Application of Tuning Fork Sensors for In-situ Studies of Dynamic Force Interactions Inside Scanning and Transmission Electron Microscopes
Mechanical properties of nanoscale contacts have been probed in-situ by specially developed force sensor based on a quartz tuning fork resonator (TF). Additional control is provided by observation of process in scanning electron microscope (SEM) and transmission electron microscope (TEM). A piezoelectric manipulator allows precise positioning of atomic force microscope (AFM) probe in contact with another electrode and recording of the TF oscillation amplitude and phase while simultaneously visualizing the contact area in electron microscope. Electrostatic control of interaction between the electrodes is demonstrated during observation of the experiment in SEM. In the TEM system the TF senso…
Nanomechanics of individual aerographite tetrapods
Carbon-based three-dimensional aerographite networks, built from interconnected hollow tubular tetrapods of multilayer graphene, are ultra-lightweight materials recently discovered and ideal for advanced multifunctional applications. In order to predict the bulk mechanical behaviour of networks it is very important to understand the mechanics of their individual building blocks. Here we characterize the mechanical response of single aerographite tetrapods via in situ scanning electron and atomic force microscopy measurements. To understand the acquired results, which show that the overall behaviour of the tetrapod is governed by the buckling of the central joint, a mechanical nonlinear mode…
Application of electrochemical impedance for characterising arrays of Bi2S3 nanowires
Abstract Electrochemical Impedance Spectroscopy (EIS) was used to characterise the electrical properties of bismuth sulphide (Bi2S3) nanowires (NWs) templated within anodic aluminium oxide (AAO) membranes. A specially engineered cell, with a nominal electrolyte volume of 0.1–0.2 ml, was used to hold and measure the electrochemical impedance of the fragile NW/AAO samples. An equivalent circuit model was developed to determine the filling density of nanowires within the porous templates. The EIS method can be utilised to probe the nanowire filling density in porous membranes over large sample areas, which is often unobtainable using electron microscopy and conductive atomic force microscopy t…
Size Distribution, Mechanical and Electrical Properties of CuO Nanowires Grown by Modified Thermal Oxidation Methods
Size distribution, Young&rsquo
Review: Electrostatically actuated nanobeam-based nanoelectromechanical switches – materials solutions and operational conditions
This review summarizes relevant research in the field of electrostatically actuated nanobeam-based nanoelectromechanical (NEM) switches. The main switch architectures and structural elements are briefly described and compared. Investigation methods that allow for exploring coupled electromechanical interactions as well as studies of mechanically or electrically induced effects are covered. An examination of the complex nanocontact behaviour during various stages of the switching cycle is provided. The choice of the switching element and the electrode is addressed from the materials perspective, detailing the benefits and drawbacks for each. An overview of experimentally demonstrated NEM swi…
Impact of granularity on transport properties of mechanically stressed La0.67Ca0.33MnO3 films
Abstract (La,Ca)MnO 3 is one of so called collosal magnetoresistive materials and it is of interest to correlate its transport properties to film growth in order to optimize its performance. Two-hundred nanometers thick (100)La 0.67 Ca 0.33 MnO 3 films were grown by laser ablation on (100)SrTiO 3 , (100)LaAlO 3 and (100)(LaAlO 3 ) 0.3 +(Sr 2 AlTaO 6 ) 0.7 substrates. The films were granular in structure with low angle boundaries between the grains. The volume of the unit cell was considerably smaller for films grown on a SrTiO 3 substrate than on LaAlO 3 . At temperatures higher than the one where the spins order, the strongest response of resistivity on temperature ρ ( T ) was measured for…
Impedance and admittance characteristics of Bi2S3 nanowire arrays
Current studies of the electrical impedance and admittance characteristics of the anodised aluminum oxide (AAO) nanoporous arrays and bismuth sulphide (Bi2S3) nanowire within AAO membranes are presented. The influence of potential and frequency scan rate effect produced on the real, imaginary and complex electrochemical impedance and double layer capacitance of the AAO nanopore and the Bi2S3 nanowire arrays were studied.
Tuning of Structural and Optical Properties of Graphene/ZnO Nanolaminates
International audience; Zinc Oxide (ZnO) and graphene (G) have been extensively studied because of their unique physical properties. Here, Graphene-Zinc Oxide (G/ZnO) nanolaminates were fabricated, respectively, by chemical vapor deposition and low temperature atomic layer deposition technique. The number of obtained G/ZnO layers was tuned from 1 to 11 with a total thickness of 100 nm for all prepared nanolaminates. The structure, optical properties and interaction between G and ZnO were studied by X-ray methods, TEM, AFM, Raman and optical spectroscopy. The obtained results were interpreted and analysed taking into account strain and charge effects of graphene in G/ZnO nanostructures. We d…
An impedance study of complex Al/Cu-Al2O3electrode
Electrochemical impedance spectroscopy (EIS) was used to investigate different Cu deposition regimes on Al surface obtained by internal electrolysis and to characterize properties of fabricated electrodes. EIS experimental data confirmed that Cu deposition by internal electrolysis is realized and the complex electrode system is obtained. The main difficulty in preparation of Al/Cu electrodes is to prevent aluminium oxidation before and during electrochemical deposition of Cu particles. In this work NaCl, CH3COONa, K2SO4, mono- and diammonium citrate electrolytes were examined to determine their suitability for impedance measurements. Al/Cu-Al2O3 electrode composition was approved by equival…
Nanowires for NEMS Switches
Nanoelectromechanical systems (NEMS) are a promising novel technology for operation in extreme conditions (e.g. high temperature and radiation levels), where complementary semiconductor technology devices might fail due to electronic instability. An example for a NEMS device is a nanowire-based switch, which employs mechanical deflection of a nanowire to open and close an electrical circuit. To date, assembly and operation of individual nanowire based NEMS switches have been successfully demonstrated at laboratory level, but their further technological development remains a challenge. This chapter gives an insight into the current advances in applications of nanowires for NEMS switches. Syn…
Fabrication of ultra thin anodic aluminium oxide membranes by low anodization voltages
Formation of ultrathin anodised aluminium oxide (AAO) membranes with high aspect ratio by Al anodization in sulphuric and oxalic acids at low potentials was investigated. Low anodization potentials ensure slow electrochemical reaction speeds and formation of AAO membranes with pore diameter and thickness below 20 nm and 70 nm respectively. Minimum time necessary for formation of continuous AAO membranes was determined. AAO membrane pore surface was covered with polymer Paraloid B72TM to transport it to the selected substrate. The fabricated ultra thin AAO membranes could be used to fabricate nanodot arrays on different surfaces.
Direct Identification of Dilute Surface Spins on Al2O3 : Origin of Flux Noise in Quantum Circuits
An on-chip electron spin resonance technique is applied to reveal the nature and origin of surface spins on Al2O3. We measure a spin density of 2.2×1017 spins/m2, attributed to physisorbed atomic hydrogen and S=1/2 electron spin states on the surface. This is direct evidence for the nature of spins responsible for flux noise in quantum circuits, which has been an issue of interest for several decades. Our findings open up a new approach to the identification and controlled reduction of paramagnetic sources of noise and decoherence in superconducting quantum devices.
Relative Humidity Dependent Resistance Switching of Bi2S3Nanowires
Electrical properties of Bi2S3nanowires grown using a single source precursor in anodic aluminum oxide templates are sensitive to the relative humidity in an inert gas environment. Dynamic sensing dependency is obtained and shows presence of spontaneous resistance switching effect between low and high relative humidity states. Employing the thermionic field emission theory, heights of Schottky barriers are estimated from the current-voltage characteristics and in relation to the humidity response. The change of Schottky barrier height is explained by local changes in physically adsorbed water molecules on the surface of the nanowire.
Zinc oxide nanorod based immunosensing platform for the determination of human leukemic cells.
Zinc oxide (ZnO) based nanostructures owing unique physical properties – high photoluminescence, bio- compatibility and other characteristics, therefore, they attract attention as building blocks suitable for biosensor development. In this research as a target we have used human leukemic cell line IM9 (IM9). IM9 was derived from the patient with a multiple myeloma and expressed cluster of differentiation proteins СD19 on the surface of 85–95% here investigated cancer cells. As a control sample healthy human's peripheral blood mononuclear cells (PBMC) were used and the expression of CD19 protein was found only in 5–9% of these cells. Two types of antibodies labeled by f…
Magnetic nanoparticles between electrodes of tunnel junction: anomalous tunnel conductance
Abstract Magnetic particles of microscopic size can be created in the process of Ni, Fe and Co mechanically controllable break junctions fabrication and trapped between the electrodes by magnetic dipole forces. Tunneling between the protruding nanoparticle and the sample electrode shows clear distinctions from the usual junctions: heavy deviation of the current–distance I(z) dependence from the expected exponential behavior at electrode separations z below 4.0– 4.5 A and on numerous occasions a sudden jump-like decrease of the tunnel current at z≈1.5– 2.0 A . Possible mechanisms behind observed anomalies including the short-range magnetic exchange coupling are discussed.
Mechanical and electroconductive properties of spatially distributed double stranded DNA arrays on Au (111)
Abstract Conductive AFM was used to investigate electroconductivity through 10 nm long double stranded DNA molecules in mixed monolayers of thioalkylated-DNA and mercaptohexanol (MCH) on Au (111) surface. The distribution of DNA molecules on the surface was analyzed by tapping mode AFM. Measurements performed in lift mode confirmed that the DNA molecules protrude from the surface rather than lie horizontally adsorbed on the interface. The optimal conductivity measurement time, which is shorter than the mechanical relaxation time of oligonucleotide duplexes, was determined. It was concluded that oligonucleotide duplexes have a resistance of the order of ~ 2 Ω ⁎ m at 1 V.
Light source inner surface changes depending on treatment
Our work is connected with the preparation of different type of electrodeless discharge lamps. In this work we investigate the influence of the SiO2 glass wall treatment procedures on the inner surface of the electrodeless lamps. Three different treatment procedures were applied: vacuum cleaning, vacuum-thermal cleaning and training in the high frequency discharge. The surface modification has been investigated by means of atomic force microscopy. Substantial changes of the SiO2 glass surface have been observed. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Colloidal nanoparticle sorting and ordering on anodic alumina patterned surfaces using templated capillary force assembly
Abstract A new, robust technique of size-selective nanoparticle ordering on porous anodized aluminum oxide (PAAO) templates is presented. Simultaneous particle sorting and array formation is achieved for the first time using a polydisperse suspension of irregularly shaped diamond nanocrystals. The array parameters can be tuned through a balance of evaporation driven particle flux, capillary, electrostatic, and adhesion forces, which are influenced by the asperities of the surface during the capillary and convective assembly dip-coating process. The resulting structures are dense (lower limit approximately 50 nm center separation), isolated (non-touching) nanoparticle arrays with a size dist…
Temperature and electric field dependence of the permittivity of Ba0.9Sr0.1TiO3 films epitaxially grown on cuprate electrodes
Abstract Cuprate, high-temperature superconductors and perovskite ferroelectrics have similar crystal structures and chemical constituents and, therefore, it can be advantageous to deposit epitaxial trilayer capacitors with high-Tc electrodes and operate these at room temperature, well above the transition temperature Tc, in order to achieve a high dielectric constant, tunability, and relatively low microwave loss. Epitaxial heterostructures (200 nm)YBa2Cu3O7−δ/(600 nm)Ba0.9Sr0.1TiO3/(200 nm)YBa2Cu3O7−δ and (200 nm)NdBa2Cu3O7−δ/(600 nm)Ba0.9Sr0.1TiO3/(200 nm)NdBa2Cu3O7−δ were laser deposited on (100)LaAlO3 substrates. The relative dielectric permittivity e/e0 of Ba0.9Sr0.1TiO3 was in the ra…
Magnetotransport Studies of Encapsulated Topological Insulator Bi2Se3 Nanoribbons
This research was funded by the Latvian Council of Science, project “Highly tunable surface state transport in topological insulator nanoribbons”, No. lzp-2020/2-0343, and by the European Union’s Horizon 2020 research and innovation program, Grant Agreement No. 766714/ HiTIMe. Institute of Solid-State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2.
Maxwell and Sharvin conductance in gold point contacts investigated using TEM-STM
We have investigated the conductance of gold point contacts using a scanning tunneling microscope ~STM! inside a transmission electron microscope ~TEM!. Measuring the conductance of these point contacts as a function of radius, we could directly compare it with theories both in the ballistic regime ~Sharvin! as well as in the diffusive regime ~Maxwell!. The width of the contacts were between a single atom and 20 nm. Using an interpolation formula ~Wexler! between the two limits, we obtain a mean free path of 4 nm, which is about ten times shorter than the room-temperature bulk value. The low value indicates an enhanced scattering, which is not due to high temperature in the point contact, i…
Resonance assisted jump-in voltage reduction for electrostatically actuated nanobeam-based gateless NEM switches.
Electrostatically actuated nanobeam-based electromechanical switches have shown promise for versatile novel applications, such as low power devices. However, their widespread use is restricted due to poor reliability resulting from high jump-in voltages. This article reports a new method for lowering the jump-in voltage by inducing mechanical oscillations in the active element during the switching ON process, reducing the jump-in voltage by more than three times. Ge0.91Sn0.09 alloy and Bi2Se3 nanowire-based nanoelectromechanical switches were constructed in situ to demonstrate the operation principles and advantages of the proposed method.
Optical and structural properties of Al 2 O 3 /ZnO nanolaminates deposited by ALD method
International audience; We report on the investigation of optical and structural properties of Al2O3/ZnO nanolaminates. The nanolaminates were deposited on Si and glass substrates by Atomic layer deposition method. Structural properties of nanolaminates were studied by SEM, GIXRD, and AFM. Optical characterization was performed by transmittance and photoluminescence spectroscopy. Complex analysis of monolayer properties was done by ellipsometry. Optical constants for Al2O3 and ZnO monolayer were calculated.
Synthesis and characterisation of ordered arrays of mesoporous carbon nanofibres
A facile and reproducible one-step pathway has been developed for preparing ordered arrays of mesoporous carbon nanostructures within the pores of anodized aluminium oxide (AAO) membranes, through the confined self-assembly of phenol/formaldehyde resol and amphiphilic copolymer templates. The morphology of the mesoporous carbon nanostructures can be controlled by varying the copolymer surfactant, the quantity of the resol–surfactant precursor sol used and the amount of phenol–formaldehyde resol introduced into the resol–surfactant sol. One-dimensional (1-D) carbon nanostructures, such as carbon fibres with a core–shell structure and carbon ribbons with circular mesopores running parallel to…
Variable Thickness Porous Anodic Alumina/Metal Film Bilayers for Optimization of Plasmonic Scattering by Nanoholes on Mirror
Continuously variable thickness porous anodic aluminum oxide (PAAO) films were obtained using electrochemical oxidation of bulk aluminum sheet while both electrodes were simultaneously withdrawn from the electrolyte solution. The thickness gradient was controlled by the withdrawal rate (1–10 mm/min range) and thickness variation demonstrated from below 50 nm to above 1 micrometer. The thickness increased linearly with the sample lateral coordinate, whereas the nanopore structure (diameter and interpore distance) remained unchanged. Effects of the initial pore growth and capillary forces are discussed. The presented method can be used for tuning optimal PAAO thickness for optical and other a…
Structure-determined thermoelectric properties of Bi2Se3 thin films deposited by vapour-solid technique
International audience; In this work, a simple catalyst-free vapour-solid deposition method is applied for controlled obtaining of two types (planar and disordered) continuous Bi2Se3 nanostructured thin films on different (fused quartz/glass, mica, graphene) substrates. Performed for the deposited thin films transport and thermoelectric characterization (type, concentration and mobility of the main charge carriers, Seebeck coefficient and power factor) showed that proposed deposition method allows to fabricate “low-doped” Bi2Se3 thin films with power factor comparable and even higher than reported for the Bi2Se3 thin films fabricated by molecular beam epitaxy technique.
<title>Metallic and semiconducting nanowires: properties and architectures</title>
Nanowires are expected to play an important role in future electronic, optical devices and nanoelectromechanical devices. Measuring the electrical and mechanical properties of nanowires is however a difficult task due to their small dimensions. Here we report the use of an in-situ microscopy technique, which combines transmission electron microscopy (TEM) with scanning probe microscopy (SPM), to investigate the electrical and mechanical properties of metallic and semiconductor nanowires. Additionally, in this paper we describe a novel approach for synthesizing mesoporous silicas with tunable pore diameters, wall thickness and pore spacings that can be used as tempates for the assembly of se…
Electric current induced modification of germanium nanowire NEM switch contact.
We present an investigation of contact properties of a germanium (Ge) nanowire based nanoelectromechanical (NEM) switch in its ON state. The contact stiffness in the ON state was evaluated by detecting the nanowire's resonance frequency. It was found that the resonance frequency increases when electric current flows through the nanowire/counter electrode contact area. The reason for modification in the contact area is referred to as electric-current-induced processes in the native oxide layer covering the nanowires. The presented resonance shift method is a simple way to indicate strengthening of the nanowire/counter electrode contact area without disassembling the contact.
Nanostructure carbon black-polyisoprene composites as prospective strain sensor materials: macro- and nanoscale studies
Nanostructured carbon black-polyisoprene composite is prepared and investigated. A giant reversible tensoresistive effect -- dependence of electrical resistance vs. uniaxial tension deformation - is found. A new application of the conductive atomic force microscope for the carbon black network mapping in a nonconducting matrix is reported.
Preparation and properties of Tl2Ba2CaCu2O8 thin films
Anex situ process has been developed to produce thin superconducting Tl2Ba2CaCu2O8 films. The properties of films grown on different substrates using different annealing regimes were studied. Critical temperatures of 103–107 K were measured on films prepared in a broad range of annealing temperatures on SrTiO3, LaAlO3, and Y-ZrO2 substrates. A critical current density,Jc, of 2×106 A/cm2 at 77 K was measured on LaAlO3. Film morphology was studied by SEM, AFM, and STM.
Photoelectrochemical Bisphenol S Sensor Based on ZnO‐Nanoroads Modified by Molecularly Imprinted Polypyrrole
Molecularly imprinted polymers are important tools for the design of sensors and other molecular recognition based analytical systems. In this paper the development of a photoelectrochemical sensor for selective bisphenol determination is reported. The sensor is based on a glass/ZnO/MIP‐Ppy structure consisting of glass modified by a ZnO layer (glass/ZnO), which is functionalized by molecularly imprinted conducting polymer polypyrrole (MIP‐Ppy). The sensitivity of the sensor to bisphenol is in the range of 0.7–12.5 µm. Selectivity tests to other bisphenolic compounds are performed. Some aspects of a photoinduced response mechanism in glass/ZnO/MIP‐Ppy nanostructures are predicte…
Effect of graphene substrate type on formation of Bi2Se3 nanoplates
AbstractKnowledge of nucleation and further growth of Bi2Se3 nanoplates on different substrates is crucial for obtaining ultrathin nanostructures and films of this material by physical vapour deposition technique. In this work, Bi2Se3 nanoplates were deposited under the same experimental conditions on different types of graphene substrates (as-transferred and post-annealed chemical vapour deposition grown monolayer graphene, monolayer graphene grown on silicon carbide substrate). Dimensions of the nanoplates deposited on graphene substrates were compared with the dimensions of the nanoplates deposited on mechanically exfoliated mica and highly ordered pyrolytic graphite flakes used as refer…
High transparency Bi 2 Se 3 topological insulator nanoribbon Josephson junctions with low resistive noise properties
Bi$_2$Se$_3$ nanoribbons, grown by catalyst-free Physical Vapour Deposition, have been used to fabricate high quality Josephson junctions with Al superconducting electrodes. The conductance spectra (dI/dV) of the junctions show clear dip-peak structures characteristic of multiple Andreev reflections. The temperature dependence of the dip-peak features reveals a highly transparent Al/Bi$_2$Se$_3$ topological insulator nanoribbon interface and Josephson junction barrier. This is supported by the high values of the Bi$_2$Se$_3$ induced gap and of I$_c$R$_n$ (I$_c$ critical current, R$_n$ normal resistance of the junction) product both of the order of 160 $\mu$eV, a value close to the Al gap. T…
A supercritical-fluid method for growing carbon nanotubes
Large‐scale generation of multiwalled carbon nanotubes (MCNTs) is efficiently achieved through a supercritical fluid technique employing carbon dioxide as the carbon source. Nanotubes with diameters ranging from 10 to 20 nm and lengths of several tens of micrometers are synthesized (see figure). The supercritical‐fluid‐grown nanotubes also exhibit field‐emission characteristics similar to MCNTs grown by chemical‐vapor deposition.
Two-terminal nanoelectromechanical bistable switches based on molybdenum–sulfur–iodine molecular wire bundles
We demonstrate the application of Mo(6)S(3)I(6) molecular wire bundles for electrically controllable two-terminal on-off switches. We investigate how changes in the contact electrode material and geometry influence the device characteristics, hysteretic switching behavior and device stability. We also determine the device operating parameters, particularly the Young's moduli (40-270 GPa), operating current densities (3.2 x 10(5)-7 x 10(6) A m(-2)) and force constants. Although qualitatively, the properties of Mo(6)S(3)I(6) nanowires in nanoelectromechanical (NEM) switches are similar to those of carbon nanotubes (CNTs), their lower friction coefficient, higher mechanical stability and highe…
Bi2Se3 Nanostructured Thin Films as Perspective Anodes for Aqueous Rechargeable Lithium-Ion Batteries
This research was funded by the European Regional Development Fund Project (ERDF) No. 1.1.1.1/19/A/139. Y.R. acknowledges the support of post-doctoral ERDF project No. 1.1.1.2/VIAA/4/20/694. V.L. also acknowledges the support of “Strengthening of the capacity of doctoral studies at the University of Latvia within the framework of the new doctoral model”, identification No. 8.2.2.0/20/I/006. A.S. acknowledges the support from the Institute of Solid State Physics, University of Latvia, which, as the Center of Excellence, has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2.
Temperature dependence of magnetization reversal in Co and Fe3O4 nanowire arrays
Abstract In this paper, we investigate the magnetization reversal of cobalt and magnetite nanowires, 4 nm in diameter, synthesized within the pores of mesoporous silica thin films. A SQUID magnetometer was used to study the magnetic properties of the nanowire arrays over a broad temperature interval, T= 1.8–300 K. The magnetization reversal process was found to be strongly temperature dependent. While a coherent rotation may occur at room temperature, a process involving the formation of domain structures takes place as the temperature decreases down to 1.8 K.
Influence of ZnO/graphene nanolaminate periodicity on their structural and mechanical properties
International audience; Structural, electronic and mechanical properties of ZnO/Graphene (ZnO/G) nanolaminates fabricated by low temperature atomic layer deposition (ALD) and chemical vapor deposition (CVD) were investigated. We performed scanning and transmission electron microscopy (SEM/TEM), X-ray diffraction (XRD), electron energy loss spectroscopy (EELS), Raman spectroscopy, X-Ray photoelectron spectroscopy (XPS) and nanoindentation to characterize the ZnO/G nanolaminates. The main structural and mechanical parameters of ZnO/G nanolaminates were calculated. The obtained results were analyzed and interpreted taking into account mechanical interaction and charge effects occurring at the …
Probing DNA conductivity with photoinduced electron transfer and scanning tunneling microscopy.
Abstract The possibility that the stacked DNA bases can mediate vectorial electron transfer has been examined using two different approaches. Experiments on photoinduced electron transfer with intercalated donors and acceptors (either randomly bound or linked dyads of ruthenium complex and viologen) indicate that while DNA may be a better medium than acetonitrile for electron transfer over short distances (2-3-base pair, equivalent to 10-14Å centre-to-centre separation), it is a poor medium for transport over larger separations. Attempts to measure conductivity of individual DNA molecules using scanning tunneling microscopy to image mixed monolayers of mercaptohexanol (MCH) and 30-mer or 10…
Raw data for the publication "Effect of graphene substrate type on formation of Bi2Se3 nanoplates", Sci. Rep. 9, 4791, 2019. https://doi.org/10.1038/s41598-019-41178-1
This dataset contains the raw AFM and SEM measurement data used for the study of stages of formation of Bi2Se3 nanoplates on different substrates and for the statistical analysis of sizes and thicknesses of the nanoplates. The results are published in Sci. Rep. 9, 4791, 2019. https://doi.org/10.1038/s41598-019-41178-1