A5057585402- Molecular Junctions and Nanostructures
- Semiconductor materials and devices
- Nanowire Synthesis and Applications
- Graphene research and applications
- Advanced Memory and Neural Computing
- Organic Electronics and Photovoltaics
- Force Microscopy Techniques and Applications
- Semiconductor materials and interfaces
- 2D Materials and Applications
- Nanofabrication and Lithography Techniques
- Quantum and electron transport phenomena
- Perovskite Materials and Applications
- Electron and X-Ray Spectroscopy Techniques
- Electronic and Structural Properties of Oxides
- Surface and Thin Film Phenomena
- Ferroelectric and Negative Capacitance Devices
- Analytical Chemistry and Sensors
- Quantum Dots Synthesis And Properties
- Conducting polymers and applications
- Organic and Molecular Conductors Research
- Chalcogenide Semiconductor Thin Films
- Advancements in Semiconductor Devices and Circuit Design
- Gas Sensing Nanomaterials and Sensors
- Advancements in Battery Materials
- Machine Learning in Materials Science
National Institute of Standards and Technology
2015-2024
Physical Measurement Laboratory
2011-2024
Theiss Research
2019-2022
United States Naval Research Laboratory
2022
Nova Research Company (United States)
2022
National Institute of Standards
2004-2018
University of Maryland, College Park
2009
Physical Sciences (United States)
2009
State Street (United States)
2008
Purdue University West Lafayette
2008
We present the results of a thorough study wet chemical methods for transferring vapor deposition grown graphene from metal growth substrate to device-compatible substrate. On basis these results, we have developed "modified RCA clean" transfer method that has much better control both contamination and crack formation does not degrade quality transferred graphene. Using this method, high device yields, up 97%, with narrow performance metrics distribution were achieved. This demonstration...
A rewriteable low-power operation nonvolatile physically flexible memristor device is demonstrated. The active component of the inexpensively fabricated at room temperature by spinning a TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> sol gel on commercially available polymer sheet. exhibits memory behavior consistent with memristor, demonstrates an on/off ratio greater than 10 000 : 1, for over 1.2 times <sup...
We report reduced contact resistance of single-layer graphene devices by using ultraviolet ozone (UVO) treatment to modify the metal/graphene interface. The were fabricated from mechanically transferred, chemical vapor deposition (CVD) grown, single layer graphene. UVO in regions as defined photolithography and prior metal was found reduce interface contamination originating incomplete removal poly(methyl methacrylate) (PMMA) photoresist. Our control experiment shows that exposure times up...
Developing processes to controllably dope transition-metal dichalcogenides (TMDs) is critical for optical and electrical applications. Here, molecular reductants oxidants are introduced onto monolayer TMDs, specifically MoS
The organic charge‐transfer complex dibenzotetrathiafulvalene–7,7,8,8‐tetracyanoquinodimethane is found to crystallize in two polymorphs when grown by physical vapor transport: the known α‐polymorph and a new structure, β‐polymorph. Structural elemental analysis via selected area electron diffraction, X‐ray photoelectron spectroscopy, polarized IR spectroscopy reveal that complexes have same stoichiometry with 1:1 donor: acceptor ratio, but exhibit unique unit cells. structural variations...
In this work, high-performance top-gated nanowire molecular flash memory has been fabricated with redox-active molecules. Different molecules one and two redox centers have tested. The clean solid/molecule dielectric interfaces, due to the pristine self-assembly device self-alignment fabrication process. cells exhibit discrete charged states at small gate voltages. Such multi-bit in cell is favorable for high-density storage. These devices fast speed, low power, long retention, exceptionally...
Controlling the morphology of metal halide perovskite layers during processing is critical for manufacturing optoelectronics. Here, a strategy to control microstructure solution-processed layered Ruddlesden-Popper-phase films based on phenethylammonium lead bromide ((PEA)
Aliphatic alcohols and aldehydes were reacted with the Si(111)-H surface to form Si-O-C interfacial bonds from dilute solution by using ultraviolet light. The resulting monolayers characterized transmission infrared spectroscopy, spectroscopic ellipsometry, contact angle measurements. effect of different solvents on monolayer quality is presented. best formed CH(2)Cl(2). optimized thoroughly determine film structure stability. UV-promoted, alcohol-functionalized, aldehyde-functionalized are...
Organic field-effect transistor (OFET) performance is dictated by its composition and geometry, as well the quality of organic semiconductor (OSC) film, which strongly depends on purity microstructure. When present, impurities defects give rise to trap states in bandgap OSC, lowering device performance. Here, 2,8-difluoro-5,11-bis(triethylsilylethynyl)-anthradithiophene used a model system study mechanism responsible for degradation OFETs due isomer coexistence. The density trapping...
MoS2 is known to show stubborn n-type behavior due its intrinsic band structure and Fermi level pinning. Here, we investigate the combined effects of molecular doping contact engineering on transport properties monolayer (ML) devices. Significant p-type (hole-transport) was only observed for chemically doped devices with high work function palladium (Pd) contacts, while low metal contacts made from titanium showed ambipolar electron favored even after prolonged p-doping treatment. ML...
Polymer passivation has been leveraged to improve photodetection in two-dimensional transition metal dichalcogenide field-effect transistors. The relative effects of common polymers, however, are not well understood. In this work, the interface monolayer MoS2 and three parylene N (Pa-N), polymethyl methacrylate (PMMA), polyvinylidene difluoride trifluoroethylene (PVDF-TrFE), is assessed with multiple spectroscopic methods. Raman photoluminescence spectroscopy demonstrate that Pa-N PMMA...
We report the fabrication of molecular electronic test structures consisting Au-molecule-Si junctions by first forming omega-functionalized self-assembled monolayers on ultrasmooth Au a flexible substrate and subsequently bonding to Si(111) with flip-chip lamination using nanotransfer printing (nTP). Infrared spectroscopy (IRS), spectroscopic ellipsometry (SE), water contact angle (CA), X-ray photoelectron (XPS) verified were dense, relatively defect-free, -COOH was exposed surface. The acid...
Resist residue from the device fabrication process is a significant source of contamination at metal/graphene contact interface. Ultraviolet Ozone (UVO) treatment proven here, by X-ray photoelectron spectroscopy and Raman measurement, to be an effective way cleaning Electrical measurements devices that were fabricated using UVO region show stable reproducible low resistance contacts are obtained electrical properties graphene channel remain unaffected.
A comprehensive analysis of the compositional heterogeneity and carrier dynamics in novel rubidium-doped 3D/2D perovskites is investigated, showing a PCE over 20% improved stability at ≈50% relative humidity without encapsulation.
The interactions between pentacene and the Si(001)-(2 × 1) surface have been investigated using Fourier transform infrared spectroscopy (FTIR), ultraviolet photoelectron (UPS), X-ray (XPS). molecules in first layer react with Si atoms through CC double bonds via cleavage of C−H bonds. This chemisorption is accompanied by disruption conjugated π electron system. disrupted interfacial stable throughout deposition evaporation thicker films. Pentacene layers beyond adsorb molecularly yield...
Vibrationally resonant sum-frequency generation (VR-SFG) and spectroscopic ellipsometry (SE) have been used to characterize self-assembled monolayer films of unsubstituted mononitro-substituted oligo(phenylene−ethynylene) molecules on vapor-deposited Au substrates. When combined with quantum chemical calculations the relevant transition moment directions, orientation distributions electronic excitation spectra are obtained. The distribution from VR-SFG is in good agreement previous IR...
A simple technique for vibrational spectroscopy of metal/monolayer/silicon structures is applied to study the interaction Au, Al, and Ti with alkane monolayers, either assembled onto thin oxides or directly attached Si. The results are correlated current−voltage capacitance−voltage measurements. Alkane films on found be robust respect deposition Au Al partially consumed during Ti. In contrast, alkoxy H-terminated Si via an ether linkage displaced by all three metals. data positively...
Reduction-oxidation (redox) active molecules hold potential for memory devices due to their many unique properties. We report the use of a novel diruthenium-based redox molecule incorporated into non-volatile Flash-based device architecture. The capacitor structure consists Pd/Al2O3/molecule/SiO2/Si structure. bulky ruthenium is attached surface by using 'click' reaction and monolayer characterized x-ray photoelectron spectroscopy verify Ru attachment molecular density. particularly...
The charge-transfer (CT) state arising as a hybrid electronic at the interface between charge donor and acceptor molecular units is important to wide variety of physical processes in organic semiconductor devices. exact nature this depends heavily on co-facial overlap acceptor; however, altering usually accompanied by extensive confounding variations properties due extrinsic factors, such microstructure. As consequence, establishing reliable relationships donor/acceptor structures, their...
Semiconductor-molecule-metal junctions consisting of alkanethiol monolayers self-assembled on both p(+) and n(-) type highly doped Si(111) wires contacted with a 10 µm Au wire in crossed-wire geometry are examined. Low temperature transport measurements reveal that molecule-induced semiconductor interface states control charge across these systems. Inelastic electron tunneling spectroscopy also highlights the strong contribution induced to observed transport.
Monolayer epitaxial graphene (EG), grown on the Si face of SiC, is an advantageous material for a variety electronic and optical applications. EG forms as single crystal over millimeter-scale areas consequently, large scale can be utilized template growth other materials. In this work, we present use to form amorphous hexagonal boron nitride (a-BN h-BN) films. The a-BN formed with pulsed laser deposition h-BN triethylboron (TEB) NH3 precursors, making it first metal organic chemical vapor...