A5018143233- Graphene research and applications
- 2D Materials and Applications
- Mechanical and Optical Resonators
- MXene and MAX Phase Materials
- Carbon Nanotubes in Composites
- Force Microscopy Techniques and Applications
- Advanced MEMS and NEMS Technologies
- Nanopore and Nanochannel Transport Studies
- Molecular Junctions and Nanostructures
- Diamond and Carbon-based Materials Research
- Nanowire Synthesis and Applications
- Advanced Sensor and Energy Harvesting Materials
- Central Venous Catheters and Hemodialysis
- Laser-Matter Interactions and Applications
- Advanced Fiber Laser Technologies
- Membrane Separation Technologies
- Thermal properties of materials
- Advanced biosensing and bioanalysis techniques
- Photonic and Optical Devices
- Vascular Procedures and Complications
- Homelessness and Social Issues
- Advanced Welding Techniques Analysis
- Quantum-Dot Cellular Automata
- DNA and Biological Computing
- Community Health and Development
Colorado State University
2025
Boston University
2013-2024
California State University, San Bernardino
2023
Washington State University Spokane
2022
NuVasive (United States)
2022
University of Massachusetts Boston
2019
Materials Science & Engineering
2019
University of Colorado Boulder
2010-2014
Cornell University
2003-2008
Universidad Autónoma de Madrid
2007
Nanoelectromechanical systems were fabricated from single- and multilayer graphene sheets by mechanically exfoliating thin graphite over trenches in silicon oxide. Vibrations with fundamental resonant frequencies the megahertz range are actuated either optically or electrically detected interferometry. We demonstrate room-temperature charge sensitivities down to 8 x 10(-4) electrons per root hertz. The thinnest resonator consists of a single suspended layer atoms represents ultimate limit...
We demonstrate that a monolayer graphene membrane is impermeable to standard gases including helium. By applying pressure difference across the membrane, we measure both elastic constants and mass of single layer graphene. This pressurized world's thinnest balloon provides unique separation barrier between 2 distinct regions only one atom thick.
We demonstrate the continuous and reversible tuning of optical band gap suspended monolayer MoS2 membranes by as much 500 meV applying very large biaxial strains. By using chemical vapor deposition (CVD) to grow crystals that are highly impermeable gas, we able apply a pressure difference across induce observe effect strain on energy intensity peaks in photoluminescence (PL) spectrum, find linear rate 99 meV/%. This method is then used study PL spectra bilayer trilayer devices under strain,...
We perform low-temperature electrical transport measurements on gated, quasi-2D graphite quantum dots. In devices with low contact resistances, we use longitudinal and Hall resistances to extract carrier densities of 9.2-13 x 10(12) cm(-2) mobilities 200-1900 cm(2)/V.s. high resistance contacts, observe Coulomb blockade phenomena infer the charging energies capacitive couplings. These experiments demonstrate that electrons in mesoscopic pieces are delocalized over nearly whole piece down...
We measured the work of separation single and few-layer MoS2 membranes from a SiOx substrate using mechanical blister test, found value 220 +- 35 mJ/m^2. Our measurements were also used to determine 2D Young's modulus layer be 160 40 N/m. then studied delamination mechanics pressurized bubles, demonstrating both stable unstable transitions between bubbles' laminated delaminated states as bubbles inflated. When they deflated, we observed edge pinning snap-in transition which are not accounted...
We have studied molecular adsorption onto stable metallic nanowires fabricated with an electrochemical method. Upon the adsorption, quantized conductance decreases, typically, to a fractional value, which may be attributed scattering of conduction electrons by adsorbates. The further change occurs when nanowire is exposed another molecule that has stronger strength. Because determined few atoms at narrowest portion each nanowire, enough conductance, used for chemical sensors.
In this paper, a method is presented to create and characterize mechanically robust, free standing, ultrathin, oxide films with controlled, nanometer-scale thickness using Atomic Layer Deposition (ALD) on graphene. Aluminum were deposited onto suspended graphene membranes ALD. Subsequent etching of the left pure aluminum only few atoms in thickness. A pressurized blister test was used determine that these ultrathin have Young's modulus 154 \pm 13 GPa. This comparable much thicker alumina ALD...
We created graphene blisters that cover and seal an annular cylinder-shaped microcavity in a SiO2 substrate filled with gas. By controlling the pressure difference between gas inside outside of microcavity, we switch membrane multiple stable equilibrium configurations. carried out experiments starting from situation where is set equal to prescribed charging pressure, p0 covers cavity like drum, adhered central post surrounding due van der Waals forces. decrease value, pe which causes it...
We study the electrical conductance of gold nanoconstrictions by controlling electrochemical potential. At positive potentials, is quantized near integer multiples G0(2e(2)/h) as shown well-defined peaks in histogram. Below a certain potential, however, additional 0.5G(0) and 1. 5G(0) appear The fractional steps are stable well defined steps. experimental data discussed terms electrochemical-potential-induced defect scattering Fermi energy shift, but complete theory phenomenon yet to be developed.
We study the mechanics of pressurized graphene membranes using an experimental configuration that allows determination elasticity and adhesion energy between a substrate (or other two-dimensional solid) membrane. The test consists monolayer membrane adhered to by surface forces. is patterned with etched microcavities prescribed volume and, when they are covered monolayer, it traps fixed number (N) gas molecules in microchamber. By lowering ambient pressure thus changing difference across...
Large arrays of 3-terminal nanoelectromechanical graphene switches are fabricated. The switch is designed with a novel geometry that leads to low actuation voltages and improved mechanical integrity, while reducing adhesion forces, which improves the reliability switch. A finite element model including non-linear electromechanics used simulate switching behavior deduce scaling relation between voltage device dimensions.
We report on a modified transfer technique for atomically thin materials integrated into microelectromechanical systems (MEMS) studying strain physics and creating strain-based devices. Our method tolerates the non-planar structures fragility of MEMS while still providing precise positioning crack-free flakes. Furthermore, our used polymer to anchor 2D crystal MEMS, which reduces fabrication time increases yield, allowed us exploit strong mechanical coupling between system. successfully...
With the ability to selectively control ionic flux, biological protein ion channels perform a fundamental role in many physiological processes. For practical applications that require functionality of channel, graphene provides promising solid-state alternative, due its atomic thinness and mechanical strength. Here, we demonstrate nanopores introduced into membranes, as large 50 nm diameter, exhibit inter-cation selectivity with ~20x preference for K+ over divalent cations can be modulated...
Using a blister test, we measured the work of separation between MoS$_2$ membranes from metal, semiconductor, and graphite substrates. We found ranging 0.11 +- 0.05 J/m^2 for chromium to 0.39 0.1 In addition, adhesion over these substrates observed dramatic difference which attribute hysteresis. Due prominent role that adhesive forces play in fabrication functionality devices made 2D materials, an experimental determination as provided here will help guide their development.
The field of two-dimensional (2D) materials has witnessed several significant advancements in a short period time. There have been extensive research efforts dedicated to this and an expanding community researchers built around the same. focus review article is on most recent milestones aspects 2D with emphasis transition metal dichalcogenides, such as improved synthesis property engineering, approaching from both experimental theoretical viewpoints. also attempt at highlighting some...
We present a unique experimental configuration that allows us to determine the interfacial forces on nearly parallel plates made from thinnest possible mechanical structures, single and few layer graphene membranes. Our approach consists of using pressure difference across membrane bring within ~10-20 nm above circular post covered with SiOx or Au until critical point is reached whereby snaps into adhesive contact post. Continuous measurements deforming an AFM coupled theoretical model allow...
Molecular transport measurements through isolated nanopores can greatly inform our understanding of how such systems select for molecular size and shape. In this work, we present a detailed analysis experimental gas permeation data single layer graphene membranes under batch depletion conditions parametric in starting pressure He, H2, Ne, CO2 between 100 670 kPa. We show mathematically that the observed intersections membrane deflection curves are indicative time dependent permeance...