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.
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…
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…
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…
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 $B$.
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.
Modelling glow curves of thermoluminescent radiometric devices
Thermoluminescent (TLD) radiation dosimeters enjoy wide usage due to low cost and simplicity of use. They however require complex device modelling in order to extract the measured dose. A new glow peak model and fit method are presented, that offer a more robust fit to the glow-curves and allows operators to enter visually inspectable parameters (rather than physical quantities difficult to estimate from the visual inspection of the glow curves themselves). Fits performed on the GLOCANIN-challenge's RefGlow-002 and RefGlow-009 [2] are presented, highlighting the good performance of the GEMINI C++ code written.
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…
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.
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…
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…
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…
Estimating the magnetic moment of microscopic magnetic sources from their magnetic field distribution in a layer of nitrogen-vacancy (NV) centres in diamond
We have used a synthetic diamond with a layer of nitrogen-vacancy (NV) centres to image the magnetic field distributions of magnetic particles on the surface of the diamond. Magnetic field distributions of 4 µ m and 2 µ m ferromagnetic and 500 nm diameter superparamagnetic particles were obtained by measuring the position of the optically detected magnetic resonance peak in the fluorescence emitted by the NV centres for each pixel. We fitted the results to a model in order to determine the magnetic moment of the particles from the magnetic field image and compared the results to the measured magnetic moment of the particles. The best-fit magnetic moment differed from the value expected base…
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.
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…
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…
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…