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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） ▾

  • Homogeneous Large-area Quasi-freestanding Monolayer and Bilayer Graphene on SiC

    摘要： In this study, we first show that the argon flow during epitaxial graphene growth is an important parameter to control the quality of the buffer and the graphene layer. Atomic force microscopy (AFM) and low-energy electron diffraction (LEED) measurements reveal that the decomposition of the SiC substrate strongly depends on the Ar mass flow rate while pressure and temperature are kept constant. Our data are interpreted by a model based on the competition of the SiC decomposition rate, controlled by the Ar flow, with a uniform graphene buffer layer formation under the equilibrium process at the SiC surface. The proper choice of a set of growth parameters allows the growth of defect-free, ultra-smooth and coherent graphene-free buffer layer and bilayer-free monolayer graphene sheets which can be transformed into large-area high-quality quasi-freestanding monolayer and bilayer graphene by hydrogen intercalation. AFM, scanning tunneling microscopy, Raman spectroscopy and electronic transport measurements underline the excellent homogeneity of the resulting quasi-freestanding layers. Electronic transport measurements in four-point probe configuration reveal a homogeneous low resistance anisotropy on both μm- and mm scales.

    关键词： SiC terrace steps,polymer assisted sublimation growth,Epitaxial graphene,freestanding bilayer graphene,argon gas flow,graphene buffer layer,monolayer graphene,resistance anisotropy,large-scale graphene growth,freestanding monolayer graphene

    更新于2025-09-23 15:22:29

  • Three-Dimensional Graphene Interconnected Structure, Fabrication Methods and Applications: Review

    摘要： Enormous amounts of research and development are currently underway in the arena of improving three-dimensional graphene and graphene oxide networks for use as foams, sponges and aerogels for a wide range of applications. The underlying reason for the interest in 3D graphene can be attributed to the splendid intrinsic and extrinsic properties brought as a result of the 3D porous structures which has given rise to high specific surface areas, good mechanical strength, fast mass and electron movement. Therefore a review about the present modes of fabrication, material properties and the applications of 3D graphene with strong emphasis on highly efficient graphene sponges and graphene foams is expounded. Following on from this, a concrete understanding of the fabrication of functionalized graphene aerogel for use in oil water separation will be addressed. To add on, the superiority of three-dimensional (3D) graphene based macro porous architectures, as an absorbent in comparison to various sorbent materials will be scrutinized. Furthermore, it was concluded that although large amounts of research and developments have been achieved thus far, there is still some room for improvement. In fact the benefits of these improvements will be applicable in a wide range of applications ranging from: high sensitivity gas detectors, super capacitors, lithium ion batteries, oil-water separators to name a few.

    关键词： GS (Graphene sponge),GO (Graphene oxide),GF (Graphene foam)

    更新于2025-09-23 15:22:29

  • Chemical Vapor Deposition for Nanotechnology || Atmospheric Pressure Chemical Vapor Deposition of Graphene

    摘要： Recently, graphene has gained significant interest owing to its outstanding conductivity, mechanical strength, thermal stability, etc. Among various graphene synthesis methods, atmospheric pressure chemical vapor deposition (APCVD) is one of the best syntheses due to very low diffusivity coefficient and a critical step for graphene-based device fabrication. High-temperature APCVD processes for thin film productions are being recognized in many diversity technologies such as solid state electronic devices, in particular, high quality epitaxial semiconductor films for silicon bipolar and metal oxide semiconductor (MOS) transistors. Graphene-based devices exhibit high potential for applications in flexible electronics, optoelectronics, and energy harvesting. In this chapter, recent advances of APCVD-based graphene synthesis and their related applications will be addressed.

    关键词： large-scale,atmospheric pressure chemical vapor deposition (APCVD),graphene,bilayer graphene (BLG),single-layer graphene (SLG),atmosphere pressure

    更新于2025-09-23 15:22:29

  • Tunable Phase Shifter Based on Few-Layer Graphene Flakes

    摘要： This letter presents a voltage-controlled tunable phase shifter based on few-layer graphene. The phase shifter consists of a stub-loaded line, composed of a microstrip line with a stub attached to it through a taper and graphene pad. The bias voltage applied to the graphene pad determines a variation of graphene resistance, which eventually causes the phase change. Without any voltage bias, graphene exhibits high resistance, thus isolating the stub and leading to a low phase shift. As the bias voltage is increased, graphene resistance is lowered, the effect of the stub is more pronounced, and the phase shift is increased. A prototype operating in the frequency range from 5 to 6 GHz has been designed and tested. The measured maximum phase shift obtained is 40°, and the corresponding degradation of the insertion loss is 3 dB.

    关键词： tunable microwave devices,graphene,phase shifter,Few-layer graphene

    更新于2025-09-23 15:22:29

  • Raman Spectroscopy || Graphene Nanocomposites Studied by Raman Spectroscopy

    摘要： The goal of this chapter is to provide a general introduction about graphene nanocomposites studied by Raman spectroscopy. The chapter will therefore begin with a brief description of the major Raman bands of carbon allotropes. In the following chapter a concise comparison between single walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), fullerenes and graphene is exposed. The characteristic features in Raman spectra of carbon allotropes, namely the intense signals D and G are investigated. In particular, the chapter will outline the Raman spectrum of graphene and different types of graphene oxide. The last part of the chapter is devoted to graphene nanocomposites.

    关键词： carbon nanotubes,graphene Raman bands,graphene oxide,polymeric nanocomposites,carbon allotropes

    更新于2025-09-23 15:22:29

  • Electroburning of few-layer graphene flakes, epitaxial graphene, and turbostratic graphene discs in air and under vacuum

    摘要： Graphene-based electrodes are very promising for molecular electronics and spintronics. Here we report a systematic characterization of the electroburning (EB) process, leading to the formation of nanometer-spaced gaps, on different types of few-layer graphene (namely mechanically exfoliated graphene on SiO2, graphene epitaxially grown on the C-face of SiC and turbostratic graphene discs deposited on SiO2) under air and vacuum conditions. The EB process is found to depend on both the graphene type and on the ambient conditions. For the mechanically exfoliated graphene, performing EB under vacuum leads to a higher yield of nanometer-gap formation than working in air. Conversely, for graphene on SiC the EB process is not successful under vacuum. Finally, the EB is possible with turbostratic graphene discs only after the creation of a constriction in the sample using lithographic patterning.

    关键词： graphene,graphene based electrodes,molecular electronics,molecular spintronics

    更新于2025-09-23 15:22:29

  • Effects of nitrogen-dopant bonding states on liquid-flow-induced electricity generation of graphene: A comparative study

    摘要： We fabricate, measure and compare the effects of the bonding states of dopant nitrogen atoms in graphene devices, specifically on the liquid-flow-induced electricity by these devices. We find that nitrogen doping enhances the voltage induced by liquid flow regardless of the nitrogen bonding state. However, different nitrogen bonding states affect graphene’s conductivity differently: while graphitic nitrogen is suitable for electricity-generation applications, pyridinic nitrogen is hopeless for this purpose, due to the formation of symmetry-breaking defects of the latter.

    关键词： Water-graphene interface,Nitrogen doped graphene,Flow-induced electricity generation

    更新于2025-09-23 15:22:29

  • On the Singular Effects in the Relativistic Landau Levels in Graphene with a Disclination

    摘要： The effect of a pseudo Aharonov-Bohm (AB) magnetic field generated by a disclination on a two-dimensional electron gas in graphene is addressed in the continuum limit within the geometric approach. The influence of the coupling between the spinor fields and the singular conical curvature is investigated, which shows that singularities have pronounced impact in the Hall conductivity. Moreover, the degeneracy related to the Dirac valleys is broken for negative values of the angular momentum quantum numbers, ?, including ? = 0. In this case, a Hall plateau develops at the null filling factor. Obtaining the Hall conductivity by summing over the positive and the negative ?'s, the null Landau level is recovered and the plateau at the null filling factor disappears. In any case, the standard plateaus, which are seen in a flat graphene are not obtained with these curvature and singular effects.

    关键词： Elastic deformations,Graphene,Landau Levels,Hall conductivity

    更新于2025-09-23 15:22:29

  • Accurate Graphene-Metal Junction Characterization

    摘要： A reliable method is proposed for measuring specific contact resistivity (ρC) for graphene-metal contacts, which is based on a contact end resistance measurement. We investigate the proposed method with simulations and confirm that the sheet resistance under the metal contact (RSK) plays an important role, as it influences the potential barrier at the graphene-metal junction. Two different complementary metal-oxide-semiconductor-compatible aluminum-based contacts are investigated to demonstrate the importance of the sheet resistance under the metal contact: the difference in RSK arises from the formation of insulating aluminum oxide (Al2O3) and aluminum carbide (Al4C3) interfacial layers, which depends on the graphene pretreatment and process conditions. Auger and X-Ray photoelectron spectroscopy (XPS) support electrical data. The method allows direct measurements of contact parameters with one contact pair and enables small test structures. It is further more reliable than the conventional transfer length method (TLM) when the sheet resistance of the material under the contact is large. The proposed method is thus ideal for geometrically small contacts where it minimizes measurement errors and it can be applied in particular to study emerging devices and materials.

    关键词： TLM,graphene,electrical contacts

    更新于2025-09-23 15:22:29

  • A Fluorescence Sensing Determination of 2, 4, 6-Trinitrophenol Based on Cationic Water-Soluble Pillar[6]arene Graphene Nanocomposite

    摘要： We describe a selective and sensitive fluorescence platform for the detection of trinitrophenol (TNP) based on competitive host–guest recognition between pyridine-functionalized pillar[6]arene (PCP6) and a probe (acridine orange, AO) that used PCP6-functionalized reduced graphene (PCP6-rGO) as the receptor. TNP is an electron-deficient and negative molecule, which is captured by PCP6 via electrostatic interactions and π–π interactions. Therefore, a selective and sensitive fluorescence probe for TNP detection is developed. It has a low detection limit of 0.0035 μM (S/N = 3) and a wider linear response of 0.01–5.0 and 5.0–125.0 for TNP. The sensing platform is also used to test TNP in two water and soil samples with satisfying results. This suggests that this approach has potential applications for the determination of TNP.

    关键词： reduced graphene,trinitrophenol,host–guest recognition,cationic pillar[6]arene

    更新于2025-09-23 15:22:29