A5009542803- 2D Materials and Applications
- Advanced Chemical Physics Studies
- Molecular Junctions and Nanostructures
- Organic Electronics and Photovoltaics
- Perovskite Materials and Applications
- Graphene research and applications
- Chalcogenide Semiconductor Thin Films
- Force Microscopy Techniques and Applications
- Surface and Thin Film Phenomena
- nanoparticles nucleation surface interactions
- Quantum Dots Synthesis And Properties
- Copper-based nanomaterials and applications
- Surface Chemistry and Catalysis
- Catalytic Processes in Materials Science
- Advanced Memory and Neural Computing
- Electronic and Structural Properties of Oxides
- Fullerene Chemistry and Applications
- Semiconductor Quantum Structures and Devices
- Electron and X-Ray Spectroscopy Techniques
- Advanced Electron Microscopy Techniques and Applications
- Chemical and Physical Properties of Materials
- Nanomaterials for catalytic reactions
- Advanced Thermodynamics and Statistical Mechanics
- Machine Learning in Materials Science
- Mechanical and Optical Resonators
Brookhaven National Laboratory
2012-2025
University of Liverpool
2016-2024
Okinawa Institute of Science and Technology Graduate University
2020-2022
Elettra-Sincrotrone Trieste S.C.p.A.
2017-2018
Center for Functional Nanomaterials
2014
Nanomaterials Research (United States)
2014
Tohoku University
2005-2010
Institute for Materials Research, Tohoku University
2005-2007
We report on the evolution of thickness-dependent electronic band structure two-dimensional layered-dichalcogenide molybdenum disulfide (MoS2). Micrometer-scale angle-resolved photoemission spectroscopy mechanically exfoliated and chemical-vapor-deposition-grown crystals provides direct evidence for shifting valence maximum from Γ to K, case MoS2 having more than one layer, single-layer MoS2, as predicted by density functional theory. This bulk few-layer monolayer had earlier been arise...
The first direct measurements are reported of the evolution thickness-dependent electronic band structure monolayers a material much current interest. Angle-resolved photoemission is performed on few-layer single-crystal dichalcogenide WSe${}_{2}$, which in class graphene-like semiconductors with desirable gap visible frequency range. These results strongly support presence predicted transition from an indirect (bulk or bilayer) to (one monolayer) gap. Values obtained for effective mass and...
Resolving the momentum degree of freedom excitons - electron-hole pairs bound by Coulomb attraction in a photoexcited semiconductor, has remained largely elusive goal for decades. In atomically thin semiconductors, such capability could probe forbidden dark excitons, which critically impact proposed opto-electronic technologies, but are not directly accessible via optical techniques. Here, we momentum-state WSe2 monolayer photoemitting their constituent electrons, and resolving them time,...
We visualize the distribution of electron around hole in an exciton and observe its elusive anomalous dispersion.
Thin Bi(001) films grown by ultrahigh vacuum deposition on Si(111)-7×7 surfaces at room temperature, were annealed ∼400K in order to improve their morphology reducing the step density surface. Annealed, well-ordered have been subsequently used as substrates for growth of pentacene (Pn). It has determined using low-energy electron microscope that Pn nucleates into a highly ordered, crystalline layer, with molecules “standing up” Bi surface, and (001) plane front. Moreover, layer is aligned...
Abstract The oxidation of CO is the archetypal heterogeneous catalytic reaction and plays a central role in advancement fundamental studies, control automobile emissions, industrial reactions. Copper‐based catalysts were first that reported to enable at room temperature, but lack stability elevated temperatures are used converters, particular loss most reactive Cu + cations, leads their deactivation. Using combined experimental theoretical approach, it shown how incorporation titanium...
In contrast to the traditional perspective that thermal fluctuations are insignificant in surface dynamics, here we report their influence on reaction dynamics. Using real-time low-energy electron microscopy imaging of NiAl(100) under both vacuum and O2 atmospheres, demonstrate transient temperature variations substantially alter direction atom diffusion between bulk, leading markedly different oxidation outcomes. During heating, substantial outward atoms from bulk results step growth....
Abstract The surface magnetization of Fe 3 GeTe 2 was examined by low-energy electron microscopy (LEEM) using an off-normal incidence beam. We found that the 180 o domain walls are Bloch type. Temperature-dependent LEEM measurements yield a with critical exponent β1 = 0.79±0.02. This result is consistent magnetism in 3D semi-infinite Heisenberg (β1 0.84±0.01) or Ising 0.78±0.02) models, which distinctly different from bulk (β 0.34±0.07). reveal power tilted beam to determine magnetic...
The rapid advancement and stringent requirements of extreme ultraviolet (EUV) lithography technology necessitate the development advanced photoresist systems for next-generation microelectronics. Recent studies have demonstrated that inorganic-based hybrid photoresists offer notable improvements in EUV sensitivity, etch resistance, greater insusceptibility to pattern collapse compared their purely organic counterparts. However, variations synthesis/coating approaches chemistry...
Type-II heterostructures (HSs) are essential components of modern electronic and optoelectronic devices. Earlier studies have found that in type-II transition metal dichalcogenide (TMD) HSs, the dominating carrier relaxation pathway is interlayer charge transfer (CT) mechanism. Here, this report shows that, a HS formed between monolayers MoSe2 ReS2, nonradiative energy (ET) from higher to lower work function material (ReS2 MoSe2) dominates over traditional CT process with without...
A key aspect of how the brain learns and enables decision-making processes is through synaptic interactions. Electrical transmission communication in a network synapses are modulated by extracellular fields generated ionic chemical gradients. Emulating such spatial interactions synthetic networks can be potential use for neuromorphic learning hardware implementation artificial intelligence. Here, we demonstrate that hydrogen-doped perovskite nickelate devices, electric bias across single...
Abstract Materials with field-tunable polarization are of broad interest to condensed matter sciences and solid-state device technologies. Here, using hydrogen (H) donor doping, we modify the room temperature metallic phase a perovskite nickelate NdNiO 3 into an insulating both metastable dipolar space-charge polarization. We then demonstrate transient negative differential capacitance in thin film capacitors. The caused by long-range movement trapping protons dominates when electric field...
High light absorption (∼15%) and strong photoluminescence (PL) emission in monolayer (1L) transition metal dichalcogenides (TMDs) make them ideal candidates for optoelectronic device applications. Competing interlayer charge transfer (CT) energy (ET) processes control the photocarrier relaxation pathways TMD heterostructures (HSs). In TMDs, long-distance ET can survive up to several tens of nm, unlike CT process. Our experiment shows that an efficient occurs from 1Ls WSe2-to-MoS2 with...
We have observed, by use of low-energy electron microscopy, the first direct evidence self-driven polycrystallization evolved from a single nucleus in case epitaxial pentacene growth on Si(111)-H terminated surface. In this Letter we demonstrate that such can develop anisotropic systems (in terms crystal structure and/or intermolecular interactions) when kinetic conditions force alignment intrinsic preferential directions along density gradient diffusing molecules. This finding gives new...
The growth of nonepitaxial as well epitaxial structures (001)-oriented pentacene (${\mathrm{C}}_{22}{\mathrm{H}}_{14}$, Pn) thin films on silicon surfaces has been extensively studied in order to elucidate the intrinsic thin-film mechanism. kinetically driven processes were found be modified significantly by anisotropy crystal structure. In situ real-time low-energy electron microscopy studies diffusion-limited Pn islands...
Abstract The role of molecular reorientation processes in the self‐assembly anisotropic molecules, such as pentacene (Pn) is studied utilizing a unique capability low‐energy electron microscopy (LEEM) for real‐time investigation film growth. In Pn on SiO 2 , layer‐by‐layer growth observed, albeit different from expected Volmer–Weber mode typical systems with lower adhesion (weak interfacial interaction). observed mechanism also than conventional concept layer‐by‐layer, or Frank van der Merwe...
Substrate engineering is a key factor in the synthesis of new complex materials. The substrate surface has to be conditioned order minimize energy threshold for formation desired phase or enhance catalytic activity substrate. mechanism activity, especially technologically relevant oxide surfaces, poorly understood. Here we design and synthesize several distinct stable CeO2 (001) reconstructions which are used grow epitaxial films high-temperature superconductor YBa2Cu3O7. film grown on...
Heterostructures (HSs) formed by the transition-metal dichalcogenide materials have shown great promise in next-generation (opto)electronic applications. An artificially twisted HS allows us to manipulate optical and electronic properties. In this work, we introduce understanding of energy transfer (ET) process governed dipolar interaction a molybdenum diselenide (MoSe
The authors have found that pentacene molecules deposited on SiO2 substrates treated with self-assembled monolayers, such as hexamethyldisilazane or octadecyltrichlorosilane, aggregate spontaneously. In situ, real-time low-energy electron microscopy investigation of the morpho-logical changes in films under ultrahigh vacuum reveals balance between film and substrate surface energies is an origin this aggregation. With situ atomic force - field effect transistor measurements, demonstrate...
The long-range surface structure of the dichalcogenide $\mathrm{Mo}{\mathrm{S}}_{2}$ is probed with nanometer-length spatial resolution using low-energy electron microscopy (LEEM) and microprobe diffraction (\ensuremath{\mu}-LEED). quality two differently prepared types $\mathrm{Mo}{\mathrm{S}}_{2}$, single-layer multilayer exfoliated crystals, as well chemical-vapor-deposition (CVD)--grown examined. effects induced by a supporting interface are examined utilizing different substrates,...
Suppression of nucleation around a gold electrode during pentacene growth on SiO2 channel is found by photoemission electron microscopy. Mass flow driven the difference between molecular orientations and gold. The poor connectivity at channel/electrode boundary causes degradation in performance field-effect transistor, which to be improved self-assembled monolayer treatment (see figure; thickness monolayers (ML)).
Doping catalytically inactive materials with dispersed atoms of an active species is a promising route toward realizing ultradilute binary catalyst systems. Beyond catalysis, strategically placed metal can accelerate wide range solid-state reactions, particularly in hydrogen storage processes. Here we analyze the role atomic Ti catalysts hydrogenation Al-based materials. We show that near Al surface activate gas-phase H(2), key step hydrogenation. By controlling placement Ti, have found...
Gold islands are typically associated with high binding affinity to adsorbates and catalytic activity. Here we present the growth of dispersed nanoscale gold on single layer MoS2, prepared an inert SiO2/Si support by chemical vapor deposition. This study offers a combination process development, optical characterization, photoelectron spectroscopy at submicron spatial resolution, advanced density functional theory modeling for detailed insight into electronic interaction between single-layer...