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oe1(光电查) - 科学论文

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出版时间
  • 2018
研究主题
  • energy distribution
  • graphene edge
  • vacuum transistor
  • Field emission
应用领域
  • Optoelectronic Information Science and Engineering
机构单位
  • Naval Research Laboratory
  • KeyW Corporation
  • Pohang University of Science and Technology (POSTECH)
1443 条数据
?? 中文（中国） ▾

  • Layer-by-Layer Graphene Growth on <i>β</i> -SiC/Si(001)

    摘要： The mechanism of few-layer graphene growth on the technologically-relevant cubic-SiC/Si(001) substrate is uncovered using high-resolution core-level and angle-resolved photoelectron spectroscopy, low-energy electron microscopy, and micro-spot low-energy electron diffraction. The thickness of the graphitic overlayer supported on the silicon carbide substrate and related changes in the surface structure are precisely controlled by monitoring the progress of the surface graphitization in-situ during high-temperature graphene synthesis, using a combination of micro-spectroscopic techniques. The experimental data reveal gradual changes in the preferential graphene lattice orientations at the initial stages of the few-layer graphene growth on SiC(001) and can act as reference data for controllable growth of single-, double-, and triple-layer graphene on silicon carbide substrates.

    关键词： LEEM,ARPES,μ-LEED,β-SiC,XPS,nanodomains,graphene

    更新于2025-09-04 15:30:14

  • Improve spectroscopic structural and AC electrical conductivity of PC/PEO blend using graphene

    摘要： Nanocomposites of polycarbonate (PC) and polyethylene oxide (PEO) embedded with graphene oxide (GO) nanopowder have been prepared using casting method. Prepared nanocomposites are studied and investigated using di?erent characterization techniques. The X-ray di?raction (XRD) pattern reveals the semi-crystalline nature of PC/PEO blend. There are no signi?cant peaks characterizing pure graphene. The intensity of the main X-ray peak characterizing the blend is decreased with the increase of graphene content con?rming a mod- i?cation in the blend due to an addition of graphene oxide. The FT-IR spectra display the main characteristic IR bands due to vibrational function groups for the components. The Optical absorption spectra are measured as a function of wavelength in the range of 190–1100 nm. The UV/V spectra show two absorption bands at 290 and 620 nm due to electronic transitions. The value of Eg is obtained using indirect transition and its decrease with increasing the amount of graphene. The behavior of ε′ and ε″ decreased with the increase of frequencies is observed. After adding graphene, the frequency is increased due to the dipole moment. The decrease of ε″ with increases of both the frequency and the temperature attributed to the origin of ε″ is the conduction losses. The decrease of dissipation factor (tan δ) is ascribed to the internal polarization mechanism related to applied fre- quencies. The maximum value of the peak at M″ relation explained as being the result of the distribution of relaxation time.

    关键词： Graphene nanopowder,AC conductivity,FT-IR,XRD,PC/PEO blend

    更新于2025-09-04 15:30:14

  • Detection of binary amino acid in aqueous solution using double gate graphene nano-ribbon field effect transistor

    摘要： The study proposes an amperometric biosensor which provides a new approach to the detection of binary amino acid using Graphene Nanoribbon Field Effect Transistor. The high dielectric properties of the binary amino acids groups (L-proline, glycine, L-alanine, and L-serine) in aqueous solution pave the way for precise detection of these molecules using the proposed nano biosensor. High dielectrics as gate insulation materials result in a change of one-dimensional electron density of the device. As a result, the presence of the amino acid groups can be realized through the change in the subthreshold swing of the nanobiosensor. The implementation of this method in Graphene nanobiosensor can be further extended in cases of other non-polar, non-charged biomolecules and acids.

    关键词： Dielectric modulation,Field effect transistor,Graphene nanoribbon,Biosensor,Binary amino acid

    更新于2025-09-04 15:30:14

  • Nitrogen-Doping Chemical Behavior of Graphene Materials with Assistance of Defluorination

    摘要： Heteroatom-doping reactions are essential to achieve advanced graphene-based materials for energy and biological areas. Unfortunately, considerably less is known regarding the detailed reaction pathways up to now. Here, we focus on investigating the nitrogen (N) doping process of fluorinated graphene (FG) under the assistance of defluorination based on modified in situ fourier transform infrared spectroscopy. It was demonstrated FG possesses a higher and more effective reactivity with ammonia in comparison with other graphene derivatives, which enable N-doping to proceed efficiently with assistance of defluorination even at a lower temperature (16.8 at % of N at 300 °C, 19.9 at % of N at 400 °C). Combining with Density functional theory, it was proved that, at the initial reaction step of N-doping, ammonia molecule attacked and substituted the C-F of FG by the new C-NH2. Sequentially, amino group was cyclized to the three-membered ring of ethylenimine. More importantly, the dissociation and migration of C-F bonds facilitates the dissociating of C-C bonds and the recombining of C-N bonds, thus significantly promoting the N atom in ethylenimine ring to transform to the pyridinic-N or graphitic-N in graphene skeleton.

    关键词： Fluorinated graphene,Reaction pathway,Defluorination,Nitrogen doping,Two-dimensional chemistry

    更新于2025-09-04 15:30:14

  • Hybridization of graphene oxide into nanogels to acquire higher photothemal effects for therapeutic delivery

    摘要： Although the special architecture of two-dimensional (2D) nanomaterials endows them with unique properties, their poor colloidal stability remains a main bottleneck to fully exploit their applications in the biomedical field. Herein, this study aims to develop a simple and effective approach to in situ incorporate 2D graphene oxide (GO) nanopletlets into thermosensitive matrix to acquire hybrid nanogels with good stability and photothermal effect. In order to improve its stability, GO firstly underwent silanization to its surface with double bonds, followed by intercalation with N-isopropylacrylamide (NIPAM) in the presence of disulfide-containing crosslinker via an emulsion method. Radical polymerization was then initiated to accelerate direct GO exfoliation in PNIPAM nanogels by forming covalent bonds between them. The well-dispersed GO nanopletlets in the nanogels not only displayed an enhanced photothermal effect, but also improved the encapsulation efficiency of an anticancer drug. The hybrid nanogels accelerate drug release under conditions mimicking the acidic/reducible solid tumor and intracellular microenvironments, most importantly, it can be further enhanced via remote photothermal treatment. The multifunctional nanogels potentiate their synergistic anticancer bioactivity as an ideal nanoplatform for cancer treatment.

    关键词： Graphene Oxide,Anticancer Drug Delivery,Photothermal Effect,Silanization,Thermosensitive Nanogels

    更新于2025-09-04 15:30:14

  • /epitaxial graphene van der Waals heterostructure

    摘要： We report on direct observation of interface superconductivity in single-unit-cell SnSe2 films grown on graphitized SiC(0001) substrate. The tunneling spectrum in the superconducting state reveals a rather conventional character with a fully gapped order parameter. The occurrence of superconductivity is further confirmed by the observation of vortices under external magnetic field. Through interface engineering, we unravel the mechanism of superconductivity that originates from a two-dimensional electron gas formed at the interface of SnSe2 and graphene. Our finding opens up novel strategies to hunt for and understand interface superconductivity based on van der Waals heterostructures.

    关键词： two-dimensional electron gas,interface superconductivity,van der Waals heterostructure,SnSe2,graphene

    更新于2025-09-04 15:30:14

  • Tuning of Graphene Work Function by Alkyl Chain Length in Amine-Based Compounds

    摘要： In this study, the effect of alkyl chain length in amine-based compounds on the work function of graphene was investigated. The graphene was synthesized by the chemical vapor deposition method. The graphene layers were functionalized by amine-based groups using a simple spin-coating method. The amine-based compounds were composed of phenyl amine and methyl-, ethyl-, propyl-, n/t-butyl-, and octyl-phenyl amine groups. Materials were confirmed by X-ray photoelectron spectroscopy to show the C and N bonding. The work function of the doped graphene layers decreased because of the effect of the doping agents. Among the doped graphene samples, t-butyl-phenyl amine functionalized graphene achieved the lowest work function of 3.89 eV (compared with 4.43 eV for pristine graphene). Further, the sheet resistance of n-doped graphene increased, confirming the high concentration of n-doping agents on the graphene layers. These results suggest the best alkyl chain is the t-butyl group to reduce the work function of graphene, and promise the use of these materials as cathodes for opto-electronic applications.

    关键词： n-doping,Graphene,Work function,Amine-based compounds

    更新于2025-09-04 15:30:14

  • Adsorption properties of O2 on the unequal amounts of binary co-doped graphene by B/N and P/N: A density functional theory study

    摘要： Graphene acts as an advanced substrate material, and it has been used as an electrode in fuel cells because it can efficiently adsorb oxygen molecules. In this study, density functional theory (DFT) calculation has been performed to exactly simulate the adsorption and dissociation of oxygen molecules on the XY3-co-doped graphene. The results show that the positively charged P and B atoms act as active sites for oxygen adsorption on the surface of graphene. In addition, PN3-G and NP3-G exhibit higher catalytic activity than the other samples because of the facile transfer of electrons from the highest occupied molecular orbital (HOMO) of O2 to the orbital above the Fermi level in the samples. More interestingly, excessive adsorption leads to the direct dissociation of oxygen molecules and making further dissociation difficult. In conclusion, the adsorption of oxygen molecules at the hollow sites on the PN3-G and NP3-G occurs via the formation of a triangular ring or trans-formation into O2? is proposed as the optimal strategy because these routes are thermodynamically favorable and the associated energy barrier is low. Furthermore, after dissociation, it was found that the oxygen atoms preferably approach the P atom. This work may be useful as a reference for future experimental studies to develop effective metal-free catalysts for fuel-cell cathodes.

    关键词： Density functional theory (DFT),XY3 co-doping,Graphene,Electron transfer,Adsorption

    更新于2025-09-04 15:30:14

  • [IEEE 2018 IEEE 13th Annual International Conference on Nano/Micro Engineered and Molecular Systems (NEMS) - Singapore, Singapore (2018.4.22-2018.4.26)] 2018 IEEE 13th Annual International Conference on Nano/Micro Engineered and Molecular Systems (NEMS) - A Novel Method for Fabricating Graphene Sensors in Channel for Biomedical Applications

    摘要： Graphene is a 2D material possessing extraordinary electrical, mechanical and optical properties which paves way for fabricate biomedical applications. A well-known method graphene-based devices is depositing graphene using chemical vapor deposition and transferring it to any substrate using polymer support like PDMS (Polydimethylsiloxane). In this process multiple wetting and drying steps are required which compromises the quality of graphene. Also, PMMA leaves residues that are difficult to remove. Here, we report a novel method to fabricate graphene sensors inside PDMS channels. In this method graphene/copper stack is bonded on a PDMS surface using mechanical pressure and temperature. This PDMS layer is then bonded to another PDMS substrate containing microchannel. Etchant is flown through the microchannel to etch the copper and obtain graphene on PDMS. The graphene obtained on PDMS is characterized using optical images, scanning electron microscopy and Raman spectroscopy. This is an easy, simple to use and scalable method to obtain graphene sensors inside microchannels for biomedical applications.

    关键词： Chemical Vapor Deposition,Biomedical Applications,Microchannel,Graphene,PDMS

    更新于2025-09-04 15:30:14

  • [IEEE 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Austin, TX, USA (2018.9.24-2018.9.26)] 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Efficient Modeling of Electron Transport with Plane Waves

    摘要： We present a method to simulate ballistic quantum transport in one-dimensional nanostructures, such as extremely scaled transistors, with a channel of nanowires or nanoribbons. In contrast to most popular approaches, we develop our method employing an accurate plane-wave basis at the atomic scale while retaining the numerical ef?ciency of a localized (tight-binding) basis at larger scales. At the core of our method is a ?nite-element expansion, where the ?nite element basis is enriched by a set of Bloch waves at high-symmetry points in the Brillouin zone of the crystal. We demonstrate the accuracy and ef?ciency of our method with the self-consistent simulation of ballistic transport in graphene nanoribbon FETs.

    关键词： graphene nanoribbon FETs,Bloch waves,finite-element expansion,plane-wave basis,ballistic quantum transport

    更新于2025-09-04 15:30:14