A5076194717- Advanced Chemical Physics Studies
- Near-Field Optical Microscopy
- Plasmonic and Surface Plasmon Research
- Spectroscopy and Laser Applications
- Spectroscopy Techniques in Biomedical and Chemical Research
- Thermal Radiation and Cooling Technologies
- Molecular Spectroscopy and Structure
- Quantum Dots Synthesis And Properties
- Graphene research and applications
- Spectroscopy and Quantum Chemical Studies
- Mechanical and Optical Resonators
- 2D Materials and Applications
- Gold and Silver Nanoparticles Synthesis and Applications
- High-pressure geophysics and materials
- Photonic and Optical Devices
- Geological and Geochemical Analysis
- Force Microscopy Techniques and Applications
- Metamaterials and Metasurfaces Applications
- Topological Materials and Phenomena
- Advancements in Battery Materials
- Astro and Planetary Science
- Electron and X-Ray Spectroscopy Techniques
- Transition Metal Oxide Nanomaterials
- Quantum and electron transport phenomena
- Acoustic Wave Resonator Technologies
Lawrence Berkeley National Laboratory
2015-2024
Berkeley College
2018
Massachusetts Institute of Technology
2005-2015
Advanced Light Source
2012
Paul Scherrer Institute
2010
Swiss Light Source
2010
Canadian Light Source (Canada)
2010
University of Saskatchewan
2010
Stanford University
2000-2006
Northwestern University
2005
Semiconductor heterostructures are the fundamental platform for many important device applications such as lasers, light-emitting diodes, solar cells, and high-electron-mobility transistors. Analogous to traditional heterostructures, layered transition metal dichalcogenide can be designed built by assembling individual single layers into functional multilayer structures, but in principle with atomically sharp interfaces, no interdiffusion of atoms, digitally controlled components, lattice...
Electrons moving in graphene behave as massless Dirac fermions, and they exhibit fascinating low-frequency electrical transport phenomena. Their dynamic response, however, is little known at frequencies above one terahertz (THz). Such knowledge important not only for a deeper understanding of the electron quantum transport, but also applications ultrahigh speed THz electronics IR optoelectronics. In this paper, we report first measurement high-frequency conductivity from to mid-IR different...
Characterizing and ultimately controlling the heterogeneity underlying biomolecular functions, quantum behavior of complex matter, photonic materials, or catalysis requires large-scale spectroscopic imaging with simultaneous specificity to structure, phase, chemical composition at nanometer spatial resolution. However, as any ultrahigh resolution microscopy technique, associated demand for an increase in both spectral bandwidth often leads a decrease desired sensitivity. We overcome this...
As a typical transition metal dichalcogenide, MoS2 offers numerous advantages for nanoelectronics and electrochemical energy storage due to its unique layered structure tunable electronic properties. When used as the anode in lithium-ion cells, undergoes intercalation conversion reactions sequence upon lithiation, reversibility of reaction is an important but still controversial topic. Here, we clarify unambiguously that not reversible, formed Li2S converted sulfur first charge process....
Solid-state batteries possess the potential to significantly impact energy storage industries by enabling diverse benefits, such as increased safety and density. However, challenges persist with physicochemical properties processes at electrode/electrolyte interfaces. Thus, there is great need characterize interfaces in situ, unveil scientific understanding that catalyzes engineering solutions. To address this, we conduct multiscale situ microscopies (optical, atomic force, infrared...
In this paper, we present a comprehensive, correlative study of the structural, transport, optical and thermoelectric properties high-quality VO2 thin films across its metal-insulator phase transition. Detailed x-ray diffraction shows that it's textured polycrystalline along [010]M1, with in-plane lattice orienting three equivalent crystallographic directions. Across transition, conductivity increases by more than 3 orders magnitude value 3.8 × 103 S/cm in metallic phase. This increase is...
Phonon polaritons are quasiparticles resulting from strong coupling of photons with optical phonons. Excitation and control these in 2D materials offer the opportunity to confine transport light at nanoscale. Here, we image phonon polariton (PhP) spectral response thin hexagonal boron nitride (hBN) crystals as a representative material using amplitude- phase-resolved scattering scanning near-field microscopy (s-SNOM) broadband mid-IR synchrotron radiation. The large bandwidth enables...
Advanced analytical capabilities of synchrotron IR spectromicroscopy meet the demands modern biological research for studying molecular reactions in individual living cells. (To listen to a podcast about this article, please go Analytical Chemistry multimedia page at pubs.acs.org/page/ancham/audio/index.html.).
The spectroscopic characterization of biomolecular structures requires nanometer spatial resolution and chemical specificity. We perform full spatio-spectral imaging dried purple membrane patches purified from Halobacterium salinarum with infrared vibrational scattering-type scanning near-field optical microscopy (s-SNOM). Using spectral phase contrast based on the Amide I resonance protein backbone, we identify distribution 20 nm few-protein sensitivity. This demonstrates general...
The physics and chemistry of liquid solutions play a central role in science, our understanding life on Earth. Unfortunately, key tools for interrogating aqueous systems, such as infrared soft X-ray spectroscopy, cannot readily be applied because strong absorption water. Here we use gas-dynamic forces to generate free-flowing, sub-micron, sheets which are two orders magnitude thinner than anything previously reported. Optical, infrared, spectroscopies used characterize the sheets, found...
Infrared spectroscopy of VO${}_{2}$ thin films at high spatial resolution shows new electronic and lattice states due to epitaxial strain that differ fundamentally from those in the bulk. This is first ultra-broadband infrared near-field study a correlated electron material, made possible by newly developed synchrotron method (SINS) on Advanced Light Source Lawrence Berkeley National Laboratory.
Scattering scanning near-field optical microscopy (s-SNOM) has emerged as a powerful imaging and spectroscopic tool for investigating nanoscale heterogeneities in biology, quantum matter, electronic photonic devices. However, many materials are defined by wide range of fundamental molecular states at far-infrared (FIR) resonant frequencies currently not accessible s-SNOM. Here we show ultrabroadband FIR s-SNOM nanoimaging spectroscopy combining synchrotron infrared radiation with novel fast...
Abstract Infrared-responsive doped metal oxide nanocrystals are an emerging class of plasmonic materials whose localized surface plasmon resonances (LSPR) can be resonant with molecular vibrations. This presents a distinctive opportunity to manipulate light–matter interactions redirect chemical or spectroscopic outcomes through the strong local electric fields they generate. Here we report technique for measuring single nanocrystal absorption spectra nanocrystals, revealing significant...
Abstract Silk protein fibres produced by silkworms and spiders are renowned for their unparalleled mechanical strength extensibility arising from high-β-sheet crystal contents as natural materials. Investigation of β-sheet-oriented conformational transitions in silk proteins at the nanoscale remains a challenge using conventional imaging techniques given limitations chemical sensitivity or limited spatial resolution. Here, we report on electron-regulated polymorphic revealed near-field...
We present a new methodology that enables studies of the molecular structure graphene-liquid interfaces with nanoscale spatial resolution. It is based on Fourier transform infrared nanospectroscopy (nano-FTIR), where (IR) field plasmonically enhanced near tip apex an atomic force microscope (AFM). The graphene seals liquid electrolyte reservoir while acting also as working electrode. photon transparency IR spectroscopy its interface liquids, including water, propylene carbonate, and aqueous...
Modern scattering-type scanning near-field optical microscopy (s-SNOM) has become an indispensable tool in material research. However, as the s-SNOM technique marches into far-infrared (IR) and terahertz (THz) regimes, emerging experiments sometimes produce puzzling results. For example, "anomalies" contrast have been widely reported. In this Letter, we systematically investigate a series of extreme subwavelength metallic nanostructures via imaging GHz to THz frequency range. We find that is...
Calcium silicate perovskite, CaSiO3, is arguably the most geochemically important phase in lower mantle, because it concentrates elements that are incompatible upper including heat-generating thorium and uranium, which have half-lives longer than geologic history of Earth. We report CaSiO3-perovskite as an approved mineral (IMA2020-012a) with name davemaoite. The natural specimen davemaoite proves existence compositional heterogeneity within mantle. Our observations indicate also hosts...