A5010268119- Surface and Thin Film Phenomena
- Advanced Chemical Physics Studies
- Graphene research and applications
- Advanced Electron Microscopy Techniques and Applications
- Crystallography and Radiation Phenomena
- nanoparticles nucleation surface interactions
- Electron and X-Ray Spectroscopy Techniques
- Magnetic properties of thin films
- Chalcogenide Semiconductor Thin Films
- Topological Materials and Phenomena
- Advanced Thermoelectric Materials and Devices
- Advanced Materials Characterization Techniques
- 2D Materials and Applications
- Quantum and electron transport phenomena
- Molecular Junctions and Nanostructures
- Catalytic Processes in Materials Science
- Physics of Superconductivity and Magnetism
- Semiconductor materials and interfaces
- X-ray Diffraction in Crystallography
- Machine Learning in Materials Science
- Color Science and Applications
- Phase-change materials and chalcogenides
- Boron and Carbon Nanomaterials Research
- Electronic and Structural Properties of Oxides
- Nanocluster Synthesis and Applications
University of Chinese Academy of Sciences
2025
Institute of Atomic and Molecular Sciences, Academia Sinica
2015-2024
Institute of Physics, Academia Sinica
2006-2024
Academia Sinica
1995-2019
National Taiwan University
1992-2018
National Yang Ming Chiao Tung University
2007-2010
National Chung Cheng University
2009
Australian National University
2008
National Taiwan Normal University
2008
National Taiwan University of Science and Technology
2008
We investigate the structural, electronic, and optical properties of hydrogen-passivated silicon nanowires along [110] [111] directions with diameter $d$ up to 4.2 nm from first principles. The size orientation dependence band gap is investigated local-density corrected $GW$ approximation. Quantum confinement becomes significant for $d<2.2\text{ }\mathrm{nm}$, where dielectric function exhibits strong anisotropy new low-energy absorption peaks start appear in imaginary part polarization wire axis.
We have carried out first-principles calculations of Pb (111) films up to 25 monolayers study the oscillatory quantum size effects exhibited in surface energy and work function. These oscillations are correlated with thickness dependence energies confined electrons, which can be properly modeled by an energy-dependent phase shift electronic wave function upon reflection at interface. It is found that a quantitative description these requires full consideration crystal band structure.
We have used the dynamical theory of low-energy electron diffraction to analyze data Si(111)7×7 surface and determined atomic structure. The method includes use symmetrized wave functions in real reciprocal spaces. Individual coordinates for first five planes (containing 200 atoms) are determined. optimized structure shows an oscillatory relaxation: with stretched bonds followed by compressed bonds. Geometric displacements from bulk dimer–adatom–stacking fault model presented.
We present first-principles calculations of silicene/graphene and germanene/graphene bilayers. Various supercell models are constructed in the order to reduce strain lattice-mismatched bilayer systems. Our energetics analysis electronic structure results suggest that graphene can be used as a substrate synthesize monolayer silicene germanene. Multiple phases single crystalline germanene with different orientations relative could coexist at room temperature. The weak interaction between...
Abstract Phase transition in thermoelectric (TE) material is a double‐edged sword—it undesired for device operation applications, but the fluctuations near an electronic instability are favorable. Here, Sb doping used to elicit spontaneous composition fluctuation showing uphill diffusion GeTe that otherwise suspended by diffusionless athermal cubic‐to‐rhombohedral phase at around 700 K. The interplay between these two transitions yields exquisite and coexistence of cubic rhombohedral phases...
Atomically uniform Pb films are successfully prepared on Si(111), despite a large lattice mismatch. Angle-resolved photoemission measurements of the electronic structure show layer-resolved quantum well states which can be correlated with dramatic variations in thermal stability. The odd film thicknesses N = 5, 7, and 9 monolayers sharp states. even 6 8 do not, but much more stable than thicknesses. This correlation is discussed terms total energy calculation Friedel-like oscillations properties.
Using density functional calculations, we demonstrate a catalytic reaction path with activation barriers of less than 0.5eV for CO oxidation on the neutral and unsupported icosahedral nanoclusters Au55, Ag55, Au25Ag30. Both O2 adsorb more strongly these clusters corresponding bulk surfaces. The consists an intermediate involving OOCO complex through which coadsorption energy is expected to play important role in reaction. Based studies Au Ag nanoclusters, model alloy nanocluster Au25Ag30 was...
Utilizing<italic>ab initio</italic>random structure searching, we investigated Li adsorption on MoS<sub>2</sub>and hydrogen molecules Li-decorated MoS<sub>2</sub>.
To exploit Rashba effect in a 2D electron gas on silicon surface for spin transport, it is necessary to have reconstruction with spin-split metallic surface-state bands. However, metals strong spin-orbit coupling (e.g., Bi, Tl, Sb, Pt) induce reconstructions almost exclusively insulating We propose strategy create bands using dense alloy layer containing metal and another modify the reconstruction. Here we report two examples, i.e., alloying Na Tl/Si(111)1 × 1 Pb. The provides new paradigm...
We invert high-energy (E\ensuremath{\ge}400 eV) photoelectron and Auger-electron interference patterns to construct 3D images of surface interface atoms. A new scheme is introduced correct the phase shift image. Image reconstruction demonstrated for Si(111) \ensuremath{\surd}3 \ifmmode\times\else\texttimes\fi{} -B, a system in which multiple-scattering effects are small all source waves equivalent. Using diffraction results from slab calculations, we achieve spatial resolution 1.0--1.3...
We present a method for spatially resolved imaging of energy-dependent photoelectron diffraction. Energy-dependent photoelectron-diffraction spectra are individually Fourier transformed to three-dimensional vector space. The complex amplitudes summed over span \ensuremath{\varphi} angles or polar angles. images are, respectively, well in the radial and azimuthal directions, directions. intersections these real-space maps fix atomic coordinates. show how intensity loci from single multiple...
The 13-atom metal clusters of fcc elements (Al, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au) were studied by density functional theory calculations. global minima searched for the ab initio random structure searching method. In addition to some new lowest-energy structures Pd13 and Au13, we found that effective coordination numbers would increase with ratio dimer-to-bulk bond length. This correlation, together electronic clusters, divides these into two groups (except which prefers a two-dimensional due...
Abstract In this work, a high thermoelectric figure of merit, zT 1.9 at 740 K is achieved in Ge 1−x Bi x Te crystals through the concurrent Seebeck coefficient enhancement and thermal conductivity reduction with dopants. The substitution for not only compensates superfluous hole carriers pristine GeTe but also shifts Fermi level ( E F ) to an eligible region. Experimentally, moderate 6–10% dopants, carrier concentration drastically decreased from 8.7 × 10 20 cm −3 3–5 boosted three times 75...
Photodriven dipole reordering of the intercalated organic molecules in halide perovskites has been suggested to be a critical degree freedom, potentially affecting physical properties, device performance, and stability hybrid perovskite-based optoelectronic devices. However, thus far direct atomically resolved mapping under operation condition, that is, illumination, is lacking. Here, we map simultaneously molecule orientation pattern electrostatic potential with atomic resolution using...
Single-crystalline SnSe has attracted much attention because of its record high figure-of-merit ZT ≈ 2.6; however, this been associated with the low mass density samples which leaves intrinsic fully dense pristine in question. To end, we prepared high-quality single crystals and performed detailed structural, electrical, thermal transport measurements over a wide temperature range along major crystallographic directions. Our were purity as confirmed via statistics 119Sn Mössbauer...
The work function of atomically uniform Ag films grown on Fe(100) is measured as a film thickness. It shows layer-resolved variations result quantum confinement the valence electrons. A first-principles calculation reproduces observed except for very thin (one and two monolayers), differences can be attributed, in part, to strain effects caused by lattice mismatch between Fe. These results illustrate close interaction interface surface properties.
Real-time in situ x-ray studies of continuous Pb deposition on Si(111)-(7x7) at 180 K reveal an unusual growth behavior. A wetting layer forms first to cover the entire surface. Then islands a fairly uniform height about five monolayers form top and grow fill The then switches layer-by-layer mode upon further deposition. This behavior alternating island can be attributed spontaneous quantum phase separation based first-principles calculation system energy.
Abstract— Field‐sequential color (FSC) is a potential technique for low‐power liquid‐crystal displays (LCDs). However, it still experiences serious visual artifact, break‐up (CBU), which degrades image quality. Consequently, the “Stencil Field‐Sequential‐Color (Stencil‐FSC)” method, applies local color‐backlight‐dimming technology at 240‐Hz field rate to FSC‐LCDs, proposed. Using Stencil‐FSC method not only suppressed CBU efficiently but also enhanced contrast ratio by using low average...
We use ab initio density-functional theory supplemented with the embedded-atom method to study self-diffusion of small clusters on (111) surface eight fcc metals. A zigzag motion is found be important in dimer and tetramer diffusions. The diffuses by a concerted motion. trimer three-atom through where only two atoms move simultaneously each step. Thus, instead increasing, migration energy lowered (or stays constant) for as compared that trimer. This novel break upwards trend predicted...
We show how the intensity enhancement of angle-resolved x-ray photoelectrons along emitter-scatterer internuclear directions can be used to monitor layer-by-layer growth Co on Cu(111). Specifically, we technique distinguish between fcc or hcp and determine precisely thickness at which stacking switches hcp. also interference patterns around each forward-focusing direction produce real-space images nearest-neighbor atoms in atomic plane above emitting atom.
Step-by-step structural information has been obtained for the growth of a metallic film on semiconductor substrate: Pb/Ge(111). Complete three-dimensional atomic coordinates have determined each equilibrium phase formed in process, from submonolayer to multilayer coverages. The quantitative model explains first time observed 30\ifmmode^\circ\else\textdegree\fi{} rotation overlayer basis vectors 1\ifmmode\times\else\texttimes\fi{}1 epitaxial Pb those two low-coverage phases.
We have carried out quantum Monte Carlo (QMC) calculations to study the interlayer interaction in a boron nitride (BN) bilayer. The binding energy, 81 meV/2BN after finite-size corrections, was found be larger than that obtained by density functional theory (DFT) with local approximation, and smaller those using van der Waals functionals, both considerable amounts. QMC calculated beyond equilibrium separation longer-range behavior all available DFT schemes.
Transition metal dichalcogenides such as the semiconductor MoS2 are a class of two-dimensional crystals. The surface morphology and quality grown by chemical vapor deposition examined using atomic force scanning tunneling microscopy techniques. By analyzing moiré patterns from several triangular islands, we find that there exist at least five different superstructures relative rotational angles between adlayer graphite substrate lattices typically less than 3°. We conclude since grows...