A5045831972- Graphene research and applications
- 2D Materials and Applications
- Advanced Memory and Neural Computing
- MXene and MAX Phase Materials
- Ferroelectric and Negative Capacitance Devices
- Quantum Dots Synthesis And Properties
- Chalcogenide Semiconductor Thin Films
- Surface and Thin Film Phenomena
- Ga2O3 and related materials
- Advanced Battery Technologies Research
- Neuroscience and Neural Engineering
- Electron and X-Ray Spectroscopy Techniques
- Electrocatalysts for Energy Conversion
- Membrane Separation Technologies
- Advanced Electron Microscopy Techniques and Applications
- Boron and Carbon Nanomaterials Research
- Quantum and electron transport phenomena
- Perovskite Materials and Applications
- Nanopore and Nanochannel Transport Studies
- Electronic and Structural Properties of Oxides
- Fuel Cells and Related Materials
- Photoreceptor and optogenetics research
Walker (United States)
2022-2025
The University of Texas at Austin
2022-2025
Material Sciences (United States)
2022
Abstract The ability to scale two-dimensional (2D) material thickness down a single monolayer presents promising opportunity realize high-speed energy-efficient memristors. Here, we report an ultra-fast memristor fabricated using atomically thin sheets of 2D hexagonal Boron Nitride, exhibiting the shortest observed switching speed (120 ps) among memristors and low energy (2pJ). Furthermore, study dynamics these ultra-short (120ps-3ns) voltage pulses, frequency range that is highly relevant...
Threshold switches based on conductive metal bridge devices are useful as selectors to block sneak leakage paths in memristor arrays used neuromorphic computing and emerging nonvolatile memory. We demonstrate that control of Ag-cation concentration Al2O3 electrolyte Ag filament size density play an important role the high on/off ratio self-compliance metal-ion-based volatile threshold switching devices. To diffusion, we inserted engineered defective graphene monolayer between electrode...
Nanopores embedded within monolayer hexagonal boron nitride (h-BN) offer possibilities of creating atomically thin ceramic membranes with unique combinations high permeance (atomic thinness), selectivity (via molecular sieving), increased thermal stability, and superior chemical resistance. However, fabricating size-selective nanopores in h-BN via scalable top-down processes remains nontrivial due to its inertness, characterizing nanopore size distribution over a large area extremely...
In the landscape of proton exchange membrane fuel cells (PEMFCs), there is a strong need for durable, low hydrogen crossover membranes that retain high current output and conductivity during operation. This study presents use UV-Ozone induced defects in graphene to eliminate penalty commonly associated with traditional mitigation strategies. We report defect engineered material demonstrates an increase hydrogen/proton selectivity 27%, decrease H2 24%, limited no impact on output....
Desalination via reverse osmosis (RO) membrane technology is a preferred solution to the ongoing global challenges of freshwater scarcity. The active separation layer RO membranes polyamide thin film (<200 nm), whose morphology critically influences performance. However, conflicting descriptions trends between and performance abound in literature due lack rigorous morphological description these membranes. Notably, comprehensive three-dimensional (3D) characterization has so far been...
Four-dimensional (4D) scanning transmission electron microscopy is used to study the electric fields at edges of 2D semiconducting monolayer MoS2. Sub-nanometer 1D features in field maps are observed outermost region along zigzag and also nanowire MoS-terminated MoS2 edges. Atomic-scale oscillations detected magnitude electromagnetic edge state, with spatial variations that depend on specific periodic reconstructions. Electric reconstructions, integrated differential phase contrast reveal...
Atomically thin 2D materials present the potential for advancing membrane separations via a combination of high selectivity (from molecular sieving) and permeance (due to atomic thinness). However, creation density precise nanopores (narrow-size-distribution) over large areas in remains challenging, nonselective leakage from nanopore heterogeneity adversely impacts performance. Here, we demonstrate protein-enabled size-selective defect sealing (PDS) atomically graphene membranes centimeter...
Defects in crystalline lattices cause modulation of the atomic density, and this leads to variations associated electrostatics at nanoscale. Mapping these spatially varying charge fluctuations using transmission electron microscopy has typically been challenging due complicated contrast transfer inherent conventional phase imaging. To overcome this, we used four-dimensional scanning (4D-STEM) measure electrostatic fields near point dislocations a monolayer. The asymmetry density (1,0) edge...
Two-dimensional (2D) materials form heterostructures in both the lateral and vertical directions when two different are interfaced, but with totally bonding mechanisms of covalent in-plane to van der Waal's layered interactions. Understanding how competition between forces influences epitaxial growth is important for future development complex mixed heterostructures. Here, we use atomic-resolution annular dark-field scanning transmission electron microscopy study detailed atomic arrangements...
Moiré superlattices in graphene arise from rotational twists stacked 2D layers, leading to specific band structures, charge density and interlayer electron excitonic interactions. The periodicities bilayer moiré lattices are given by a simple basis vector that describes periodic oscillations atomic density. addition of third layer form trilayer generates lattice comprised multiple harmonics do not occur systems, nontrivial crystal symmetries. Here, we use resolution 4D-scanning transmission...
Resistive switching in 2D materials such as hexagonal boron nitride (hBN) and Transition Metal Dichalcogenides (TMDs) have been demonstrated recently [1]–[3]. These memory devices with an ultra-thin layer the potential to achieve low operating voltages, variability are also suitable for flexible electronic applications [4]. Here we report first experimental observation of sub-nanosecond hBN based resistive random access (RRAM) devices. This is fastest speed RRAMs, surpassing previously...
Low-temperature large-area growth of two-dimensional (2D) transition-metal dichalcogenides (TMDs) is critical for their integration with silicon chips. Especially, if the temperatures can be lowered below back-end-of-line (BEOL) processing temperatures, Si transistors interface 2D devices (in back end) to enable high-density heterogeneous circuits. Such configurations are particularly useful neuromorphic computing applications where a dense network neurons interacts compute output. In this...
Palladium selenides, relatively unexplored platinum group metal chalcogenides, have been attracting significant interest due to their versatility in different applications and numerous stable phases with crystal structures. Most vapor-based bottom-up growth approaches using furnaces resulted the layered PdSe2 phase reactions occurring a saturated chalcogen vapor environment, which is most phase. Here, we show that precise control over Pd/Se stoichiometry can be achieved through tuning flux,...
Abstract Artificially introduced small twist angles at the interfaces of vertical layered heterostructures (VLHs) have allowed deterministic tuning electronic and optical properties such as strongly correlated phases Moiré excitons. But creating a in van der Waals (vdWs) systems by manual stacking is challenging reproducibility, uniformity, accuracy angle, which hinders future studies. Here, it demonstrated that contrary to commonly believed 0°‐orientation vdWs epitaxy, these VLHs show...