A5087559449- Graphene research and applications
- Quantum and electron transport phenomena
- Advancements in Semiconductor Devices and Circuit Design
- Surface and Thin Film Phenomena
- 2D Materials and Applications
- Semiconductor Quantum Structures and Devices
- Semiconductor materials and devices
- Physics of Superconductivity and Magnetism
- Topological Materials and Phenomena
- Quantum Dots Synthesis And Properties
- Perovskite Materials and Applications
- Plasmonic and Surface Plasmon Research
- Advanced Memory and Neural Computing
- Chalcogenide Semiconductor Thin Films
- Nanowire Synthesis and Applications
- ZnO doping and properties
- MXene and MAX Phase Materials
- Thermal properties of materials
- Carbon Nanotubes in Composites
- Electron and X-Ray Spectroscopy Techniques
- Electronic and Structural Properties of Oxides
- Magnetic and transport properties of perovskites and related materials
- Molecular Junctions and Nanostructures
- Graphene and Nanomaterials Applications
- Magnetic properties of thin films
Sungkyunkwan University
2016-2025
Korea Advanced Nano Fab Center
2016-2022
University of Maryland, College Park
2010-2020
Joint Quantum Institute
2014-2019
Northwestern University
2016
Suwon Research Institute
2014
Samsung (South Korea)
2014
Kyung Hee University
2012
Kavli Institute for Particle Astrophysics and Cosmology
2009
Kumoh National Institute of Technology
1992
A broad review of fundamental electronic properties two-dimensional graphene with the emphasis on density and temperature-dependent carrier transport in doped or gated structures is provided. salient feature this a critical comparison between semiconductor systems (e.g., heterostructures, quantum wells, inversion layers) so that unique features arising from its gapless, massless, chiral Dirac spectrum are highlighted. Experiment theory, as well semiclassical transport, discussed synergistic...
The dynamical dielectric function of two-dimensional graphene at arbitrary wave vector $q$ and frequency $\ensuremath{\omega}$, $ϵ(q,\ensuremath{\omega})$, is calculated in the self-consistent-field approximation. results are used to find dispersion plasmon mode electrostatic screening Coulomb interaction (2D) layer within random-phase At long wavelengths $(q\ensuremath{\rightarrow}0)$, shows local classical behavior ${\ensuremath{\omega}}_{\mathit{cl}}={\ensuremath{\omega}}_{0}\sqrt{q}$,...
Carrier transport in gated 2D graphene monolayers is considered the presence of scattering by random charged impurity centers with density ${n}_{i}$. Excellent quantitative agreement obtained (for carrier $n>{10}^{12}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}2}$) existing experimental data. The conductivity scales linearly $n/{n}_{i}$ theory. We explain experimentally observed asymmetry between electron and hole conductivities, high-density saturation for highest mobility samples....
We demonstrate theoretically that most of the observed transport properties graphene sheets at zero magnetic field can be explained by scattering from charged impurities. find that, contrary to common perception, these are not universal but depend on concentration impurities n(imp). For dirty samples (250 x 10(10) cm(-2) < n(imp) 400 cm(-2)), value minimum conductivity low carrier density is indeed 4e(2)/h in agreement with early experiments, weak dependence impurity concentration. cleaner...
The conductivity of graphene samples with various levels disorder is investigated for a set specimens mobility in the range 1-20x10(3) cm2/V sec. Comparing experimental data theoretical transport calculations based on charged impurity scattering, we estimate that concentration varies from 2-15x10(11) cm(-2). In low carrier density limit, exhibits values 2-12e2/h, which can be related to residual induced by inhomogeneous charge distribution samples. shape curves indicates high contain some...
A high-performance novel photodetector is demonstrated, which consists of graphene and CH3 NH3 PbI3 perovskite layers. The resulting hybrid exhibits a dramatically enhanced photo responsivity (180 A/W) effective quantum efficiency (5× 10(4) %) over broad bandwidth within the UV visible ranges.
We theoretically calculate the phonon scattering limited electron mobility in extrinsic (i.e., gated or doped with a tunable and finite carrier density) two-dimensional graphene layers as function of temperature $(T)$ density $(n)$. find temperature-dependent phonon-limited resistivity ${\ensuremath{\rho}}_{\mathit{ph}}(T)$ to be linear for $T\ensuremath{\gtrsim}50\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ room-temperature intrinsic reaching values above...
For the application of graphene quantum dots (GQDs) to optoelectronic nanodevices, it is critical importance understand mechanisms which result in novel phenomena their light absorption/emission. Here, we present size-dependent shape/edge-state variations GQDs and visible photoluminescence (PL) showing anomalous size dependences. With varying average (da) from 5 35 nm, peak energy absorption spectra monotonically decreases, while that PL unusually shows nonmonotonic behaviors having a...
In spite of recent significant research into various two-dimensional (2D) materials after the emergence graphene, development a new 2D material that provides both high mobility and an appropriate energy band gap (which are crucial for device applications) remains elusive. this report, we demonstrate carrier transport behaviour Ti2CTx, which belongs to family transition metal carbides nitrides, can be tuned by modifying surface group Tx (–OH, –F, –O). Our results show Ti2C(OH)xFy Ti2COx films...
We survey the electronic structure and magnetic properties of two-dimensional (2D) $M\mathrm{P}{X}_{3}$ ($M=\text{V},\text{Cr},\text{Mn},\text{Fe},\text{Co},\text{Ni},\text{Cu},\text{Zn}$, $X=\text{S},\text{Se},\text{Te}$) transition-metal chalcogenophosphates to shed light on their potential role as single-layer van der Waals materials that possess order. Our ab initio calculations predict most these are antiferromagnetic semiconductors. The band gaps states decrease atomic number chalcogen...
We fabricated dye-sensitized MoS2 photodetectors that utilized a single-layer treated with rhodamine 6G (R6G) organic dye molecules (with an optical band gap of 2.38 eV or 521 nm). The proposed photodetector showed enhanced performance broad spectral photoresponse and high photoresponsivity compared the properties pristine photodetectors. R6G deposited onto layer increased photocurrent by order magnitude due to charge transfer photoexcited electrons from layer. Importantly, photodetection...
We study the effect of electron-acoustic phonon interactions in twisted bilayer graphene on resistivity high-temperature transport and superconductivity low-temperature phase diagram. theoretically show that should have an enhanced strongly twist-angle dependent linear-in-temperature metallic regime with magnitude increasing as twist angle approaches magic angle. The slope versus temperature could approach one hundred ohms per kelvin a strong dependence, but rather weak dependence carrier...
Colloidal Ag(In,Ga)S2 nanocrystals (AIGS NCs) with the band gap tunability by their size and composition within visible range have garnered surging interest. High absorption cross-section narrow emission linewidth of AIGS NCs make them ideally suited to address challenges Cd-free in wide-ranging photonic applications. However, shown relatively underwhelming photoluminescence quantum yield (PL QY) date, primarily because coherent heteroepitaxy has not been realized. Here, we report for...
We calculate magnetization in magnetically doped semiconductors assuming a local exchange model of carrier-mediated ferromagnetic mechanism and using number complementary theoretical approaches. In general, we find that the results our mean-field calculations, particularly dynamical mean field theory results, give excellent qualitative agreement with experimentally observed systems itinerant charge carriers, such as Ga_{1-x}Mn_xAs 0.03 < x 0.07, whereas percolation-theory-based calculations...
We calculate the temperature-dependent conductivity of graphene in presence randomly distributed Coulomb impurity charges arising from screening disorder without any phonons. The purely electronic temperature dependence our theory arises two independent mechanisms: explicit finite-temperature dielectric function $\ensuremath{\epsilon}(q,T)$ and energy averaging transport scattering time. find that calculated is nonmonotonic, decreasing with at low temperatures, increasing high temperatures....
We consider theoretically the electron-electron interaction induced many-body effects in undoped (``intrinsic'') and doped (``extrinsic'') two-dimensional (2D) graphene layers. find that (1) intrinsic is a marginal Fermi liquid with imaginary part of self-energy, $\mathrm{Im}\phantom{\rule{0.2em}{0ex}}\ensuremath{\Sigma}(\ensuremath{\omega})$, varying linearly energy $\ensuremath{\omega}$ for small $\ensuremath{\omega}$, implying quasiparticle spectral weight vanishes at Dirac point as...
We derive the plasmon dispersion in doped double-layer graphene (DLG), made of two parallel monolayers with carrier densities ${n}_{1}$ and ${n}_{2}$, respectively, an interlayer separation $d$. The linear chiral gapless single-particle energy leads to DLG properties several unexpected experimentally observable characteristic features such as a nontrivial influence undoped $({n}_{2}=0)$ layer on strange second even weak-coupling $d\ensuremath{\rightarrow}\ensuremath{\infty}$ limit. At long...
We develop a theory for the long-wavelength plasma oscillation of collection charged massless Dirac particles in solid, as occurring, example, doped graphene layers, interacting via long-range Coulomb interaction. find that plasmon frequency such is explicitly nonclassical all dimensions with being proportional to 1/sqrt[variant Planck's over 2pi]. also show D-dimensional superlattice made from does not agree corresponding D + 1-dimensional bulk frequency. compare and contrast plasmons...
We calculate within the Boltzmann equation approach charged impurity-scattering-limited low-temperature electronic resistivity of low-density $n$-type inversion layers in Si MOSFET structures. find a rather sharp quantum to classical crossover transport behavior $0--5\mathrm{K}$ temperature range, with low-density, mobility showing strikingly strong nonmonotonic dependence, which may qualitatively explain recently observed anomalously dependent high-mobility MOSFETs.
We theoretically calculate and compare the single particle relaxation time $({\ensuremath{\tau}}_{s})$ defining quantum level broadening transport scattering $({\ensuremath{\tau}}_{t})$ Drude conductivity in two-dimensional (2D) graphene layers presence of screened charged impurity short-range defect scattering. find that ratio ${\ensuremath{\tau}}_{t}∕{\ensuremath{\tau}}_{s}$ strongly increases with increasing ${k}_{F}{z}_{i}$ $\ensuremath{\kappa}$, where ${k}_{F}$, ${z}_{i}$,...
Motivated by a recent experiment reporting on the possible application of graphene as sensors, we calculate transport properties two-dimensional monolayers in presence adsorbed molecules. We find that molecules, acting compensators partially neutralize random charged impurity centers substrate, enhance mobility without much change carrier density. predict subsequent field-effect measurements should preserve this higher for both electrons and holes, but with voltage induced electron-hole...
Motivated by recent experiments [1-3] we calculate the thermopower of graphene incorporating energy dependence various transport scattering times. We find that screened charged impurities gives a reasonable explanation for measured thermopower. The calculated behaves as 1/\sqrt{n} at high densities, but saturates low densities. also scales with normalized temperature T/T_F and does not depend on impurity strongly depends fine structure constant r_s location impurities. discuss deviation from...