A5073291364- Molecular Junctions and Nanostructures
- Electrochemical Analysis and Applications
- Nanowire Synthesis and Applications
- Quantum Dots Synthesis And Properties
- Quantum and electron transport phenomena
- Organic Electronics and Photovoltaics
- Semiconductor materials and devices
- Gold and Silver Nanoparticles Synthesis and Applications
- Electrochemical sensors and biosensors
- Electrocatalysts for Energy Conversion
- Quantum-Dot Cellular Automata
- Graphene research and applications
- Carbon Nanotubes in Composites
- Advanced Memory and Neural Computing
- Analytical Chemistry and Sensors
- Organic Light-Emitting Diodes Research
- Carbon and Quantum Dots Applications
- Photonic and Optical Devices
- Luminescence and Fluorescent Materials
- Advanced MEMS and NEMS Technologies
- Tribology and Wear Analysis
- Electrowetting and Microfluidic Technologies
- Nanocluster Synthesis and Applications
- Advanced Physical and Chemical Molecular Interactions
- Chemical Safety and Risk Management
National Institute for Nanotechnology
2013-2024
National Research Council Canada
2009-2024
University of British Columbia
2022-2024
Okanagan University College
2024
University of Alberta
2007-2020
Alberta Hospital Edmonton
2019-2020
Iowa State University
2005-2008
Ames National Laboratory
2005-2008
The Ohio State University
2007
University of Utah
2007
Molecular electronics seeks to incorporate molecular components as functional elements in electronic devices. There are numerous strategies reported date for the fabrication, design, and characterization of such devices, but a broadly accepted example showing structure-dependent conductance behavior has not yet emerged. This progress report focuses on experimental methods making both single-molecule ensemble junctions, highlights key results from these efforts. Based some general objectives...
A simple benchtop method of fabricating glass-sealed nanometer-sized Au and Pt disk electrodes, glass nanopore membranes is reported. The synthesis all three structures initiated by sealing the tips electrochemically sharpened microwires into at end a soda lime or lead capillary. nanodisk electrodes are obtained hand polishing using high-input impedance metal oxide semiconductor field effect transistor (MOSFET)-based circuit to monitor radius disk. Proper biasing MOSFET circuit, based on...
In this work, we bridge the gap between short-range tunneling in molecular junctions and activated hopping bulk organic films, greatly extend distance range of charge transport electronic devices. Three distinct mechanisms were observed for 4.5-22-nm-thick oligo(thiophene) layers carbon contacts, with operative when d < 8 nm, > 16 nm high temperatures low bias, a third mechanism consistent field-induced ionization highest occupied orbitals or interface states to generate carriers = 8-22 nm....
The promise of molecular electronic devices stems from the possibilities offered by rich structure organic molecules. use molecules as functional components in microelectronic has long been envisioned to augment or even replace silicon. However, understanding what controls charge transport these involves complexities stemming numerous variables that are often interactive and exert a controlling influence on transport, confounding role component. This perspective discusses various aspects...
Molecular junctions are essentially modified electrodes familiar to electrochemists where the electrolyte is replaced by a conducting “contact.” It generally hypothesized that changing molecular structure will alter system energy levels leading change in transport barrier. Here, we show conductance of seven different aromatic molecules covalently bonded carbon implies modest range (< 0.5 eV) observed barrier despite widely free molecule HOMO energies (> 2 eV range). These results...
This Article explores the idea of using nonmetallic contacts for molecular electronics. Metal-free, all-carbon electronic junctions were fabricated by orienting a layer organic molecules between two carbon conductors with high yield (>90%) and good reproducibility (rsd current density at 0.5 V <30%). These devices exhibit density-voltage (J-V) behavior similar to those metallic Cu top contacts. However, display enhanced stability bias extremes greatly improved thermal stability. Completed...
Molecular junctions that have a non-linear current–voltage characteristic consistent with quantum mechanical tunneling are demonstrated as analog audio clipping elements in overdrive circuits widely used electronic music, particularly electric guitars. The performance of large-area molecular fabricated at the wafer level is compared to currently standard semiconductor diode clippers, showing difference sound character. harmonic distributions resulting from use traditional and reported...
This paper reports the electron transport characteristics of carbon/molecule/Cu molecular junctions, where aromatic molecules (azobenzene or AB and nitroazobenzene NAB) are employed as component. It is shown that these devices can be made with high yield (>90%), display excellent reproducibility, withstand at least 1.5 × 109 potential cycles temperatures 180 °C. Transport mechanisms investigated by analysis current density/voltage (J−V) curves a function layer thickness temperature. Results...
Successful integration of proteins in solid-state electronics requires contacting them a non-invasive fashion, with solid conducting surface for immobilization as one such contact. The contacts can affect and even dominate the measured electronic transport. Often substrates, substrate treatments, protein immobilization, device geometries differ between laboratories. Thus question arises how far results from different laboratories platforms are comparable to distinguish genuine transport...
This paper presents results showing that the design of substrates used for surface-enhanced Raman spectroscopy (SERS) can impact apparent enhancement factors (EFs) obtained due to optical interference effects are distinct from SERS, providing additional intensity. Thus, a combination SERS and substrate designed maximize interference-based is demonstrated give intensity above observed alone. The system explored 4-nitroazobenzene (NAB) biphenyl (BP) chemisorbed on nanostructured silver film by...
Graphene quantum dots with tunable photoluminescence and hydrophobicity were synthesized from an abundant natural carbon source containing nitrogen, sulfur, oxygen heteroatoms.
Evaporation of Cu metal onto thin (less than 5 nm) molecular layers bonded to conductive carbon substrates results in electronic junctions with an ensemble molecules sandwiched between two conductors. The resulting devices have previously been characterized through analysis current density-voltage (j-V) curves for several different and as a function layer thickness. approach represents 'ensemble' rather 'single molecule' technique, which the response that large number (10(6)-10(12)) parallel...
Molecular electronics seeks to build circuitry using organic components with at least one dimension in the nanoscale domain. Progress field has been inhibited by difficulty determining energy levels of molecules after being perturbed interactions conducting contacts. We measured photocurrent spectra for large-area aliphatic and aromatic molecular tunnel junctions partially transparent copper top Where no absorption takes place, is dominated internal photoemission, which exhibits thresholds...
This paper presents a method to derivatize wide variety of substrate materials that are frequently used in spectroscopic characterizations with molecular layers through the reduction aromatic diazonium reagents. The relies on an ultrathin (5 nm) layer reactive metal (e.g., Ti or Al) deposited as primer subsequently mediates reagents from acetonitrile solution. Following surface modification, can be oxidized provide passivated support surface. Raman, Infrared, UV-vis and X-ray photoelectron...
This review discusses the analytical characterization of molecular electronic devices and structures relevant thereto. In particular, we outline methods for probing junctions, which contain an ensemble molecules between two contacts. We discuss that aid in fabrication beginning with confirmation placement a layer on conductive or semiconductive substrate. emphasize provide information about junction techniques to ensure integrity after complete device. addition, derived during actual device...
Abstract Reproducible carbon/molecule/Cu molecular junctions are made with high yield using diazonium reduction of aromatic molecules on carbon direct evaporation Cu as a top contact. This report investigates the stability these devices in response to fabrication steps. Raman spectroscopy through transparent support shows that deposition Au or causes little change layer structure, while Ti and Pt cause significant damage molecules. AFM, Raman, XPS examination Au, Cu, after removal deposited...
Visible light emission was observed for molecular junctions containing 5–19 nm thick layers of aromatic molecules between carbon contacts and correlated with their current–voltage behaviors. Their compared to that from Al/AlOx/Au tunnel junctions, which has been previously attributed transport carriers across the AlOx layer yield "hot carriers" emit as they relax within Au contact. The maximum emitted photon energy is equal applied bias case coherent tunneling, such behavior thin (<5 nm)...
The photocurrent spectra for large-area molecular junctions are reported, where partially transparent copper top contacts permit illumination by UV-vis light. effect of variation the structure and thickness discussed. Internal photoemission (IPE), a process involving optical excitation hot carriers in followed transport across internal system barriers, is dominant when component does not absorb IPE spectrum contains information regarding energy level alignment within complete, working...
Carbon has always been an important electrode material for electrochemical applications, and the relatively recent development of carbon nanotubes graphene as electrodes significantly increased interest in field. solids, both sp(2) sp(3) hybridized, are unique their combination electronic conductivity ability to form strong bonds a variety other elements molecules. The Faraday Discussion included broad concepts applications materials electrochemistry, including analysis, energy storage,...
Integrated sensing can be realized in a digital microfluidic (DMF) system not by adding components or materials to the DMF system, but judiciously removing portions of ground plane create microwave-resonant structures.
Pyrolysis of diluted commercial photoresist spun onto quartz slides yields optically transparent graphitic films. Transparent carbon electrodes approximately 6 nm thick can be reproducibly prepared, with a maximum absorbance in the ultraviolet-visible (UV-vis) range 0.25 at 270 nm. These are sufficiently conductive for electrochemistry, enabling modification surface via diazonium ion reduction and spectroelectrochemistry. Good quality absorption spectra covalently bonded molecular layers...
Large-area molecular electronic junctions consisting of 5-carbon wide graphene ribbons (GR) with lengths 2–12 nm between carbon electrodes were fabricated by electrochemical reduction diazotized 1,8-diaminonaphthalene. Their conductance greatly exceeds that observed for other similar thicknesses, a factor >1 × 104 compared to polyphenylenes and 107 alkane chains. The remarkable increase the GR nanolayer results from (i) uninterrupted planarity fused-arene structure affording extensive...
Emission of visible light from large area molecular junctions provides a direct measure the energy carriers when they encounter conducting contact and stimulate photon emission. For carbon/molecule/carbon containing aromatic layers with thicknesses less than 5 nm, transport is elastic, maximum emitted (i.e., “cut‐off” energy, hv co ) equal to eV app , where V bias across junction. increases monotonically symmetric polarity, but weakly dependent on nature material. Light emission oligomeric...
This paper discusses the electronic properties of molecular devices made using covalently bonded layers on carbon surfaces with evaporated silicon top contacts. The Cu "top contact" previously reported carbon/molecule/Cu was replaced e-beam deposited Si in order to avoid oxidation or electromigration, and provide further insight into electron transport mechanisms. fabrication characterization is detailed, including a spectroscopic assessment layer integrity after contact deposition....