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- 2018
- energy distribution
- graphene edge
- vacuum transistor
- Field emission
- Optoelectronic Information Science and Engineering
- Naval Research Laboratory
- KeyW Corporation
- Pohang University of Science and Technology (POSTECH)
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Tunnel spectroscopy of localised electronic states in hexagonal boron nitride
摘要： Hexagonal boron nitride is a large band gap layered crystal, frequently incorporated in van der Waals heterostructures as an insulating or tunnel barrier. Localised states with energies within its band gap can emit visible light, relevant to applications in nanophotonics and quantum information processing. However, they also give rise to conducting channels, which can induce electrical breakdown when a large voltage is applied. Here we use gated tunnel transistors to study resonant electron tunnelling through the localised states in few atomic-layer boron nitride barriers sandwiched between two monolayer graphene electrodes. The measurements are used to determine the energy, linewidth, tunnelling transmission probability, and depth within the barrier of more than 50 distinct localised states. A three-step process of electron percolation through two spatially separated localised states is also investigated.
关键词： quantum information processing,hexagonal boron nitride,tunnel spectroscopy,localised electronic states,graphene
更新于2025-09-04 15:30:14
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High-Performance PEDOT:PSS/Hexamethylene Diisocyanate-Functionalized Graphene Oxide Nanocomposites: Preparation and Properties
摘要： Graphene oxide (GO) has emerged as an ideal ?ller to reinforce polymeric matrices owing to its large speci?c surface area, transparency, ?exibility, and very high mechanical strength. Nonetheless, functionalization is required to improve its solubility in common solvents and expand its practical uses. In this work, hexamethylene diisocyanate (HDI)-functionalized GO (HDI-GO) has been used as ?ller of a conductive polymer matrix, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The nanocomposites have been prepared via a simple solution casting method, and have been characterized by scanning electron microscopy (SEM), UV–Vis and Raman spectroscopies, X-ray diffraction (XRD), thermogravimetric analysis (TGA), tensile tests, and four-point probe measurements to get information about how the HDI-GO functionalization degree (FD) and the HDI-GO concentration in the nanocomposite in?uence the ?nal properties. SEM analysis showed a very homogenous dispersion of the HDI-GO nanosheets with the highest FD within the matrix, and the Raman spectra revealed the existence of very strong HDI-GO-PEDOT:PSS interactions. A gradual improvement in thermal stability was found with increasing HDI-GO concentration, with only a small loss in transparency. A reduction in the sheet resistance of PEDOT:PSS was found at low HDI-GO contents, whilst increasing moderately at the highest loading tested. The nanocomposites showed a good combination of stiffness, strength, ductility, and toughness. The optimum balance of properties was attained for samples incorporating 2 and 5 wt % HDI-GO with the highest FD. These solution-processed nanocomposites show considerably improved performance compared to conventional PEDOT:PSS nanocomposites ?lled with raw GO, and are highly suitable for applications in various ?elds, including ?exible electronics, thermoelectric devices, and solar energy applications.
关键词： hexamethylene diisocyanate,PEDOT:PSS,functionalization degree,nanocomposite,optical transmittance,sheet resistance,graphene oxide,mechanical properties
更新于2025-09-04 15:30:14
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Graphene Synthesis by Plasma-Enhanced CVD Growth with Ethanol
摘要： A modified route to synthesize graphene flakes is proposed using the Chemical Vapor Deposition (CVD) technique, by using copper substrates as supports. The carbon source used was ethanol, the synthesis temperature was 950°C and the pressure was controlled along the whole process. In this CVD synthesis process the incorporation of the carbon source was produced at low pressure and 950°C inducing the appearance of a plasma blue flash inside the quartz tube. Apparently, the presence of this plasma blue flash is required for obtaining graphene flakes. The synthesized graphene was characterized by different techniques, showing the presence of non-oxidized graphene with high purity.
关键词： Chemical Vapor Deposition,Raman Spectroscopy,AFM,Plasma-Enhanced,Graphene Flakes
更新于2025-09-04 15:30:14