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- 2018
- energy distribution
- graphene edge
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- Naval Research Laboratory
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- Pohang University of Science and Technology (POSTECH)
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Improved Retention Performance in Graphene-Ferroelectric Memory Device Through Mitigation of the Surface Roughness of the Ferroelectric Layer
摘要： A ferroelectric-gated graphene field-effect transistor was fabricated with a bottom-gate structure. A ferroelectric gate dielectric was formed using the spin-coating method. Two samples were made, one with a single coating and the other with a double coating. It was observed that the data retention times of the two samples were significantly different. When comparing the surface roughness, the surface of the thin film produced by the double coating was much flatter. Based on the observation of the surface morphology, an interfacial layer composed of air was deduced as the origin of both the depolarization and short retention time. That is, when fabricating the graphene-ferroelectric memory device, the importance of the interface treatment could be confirmed. Based on these results, it is expected that a much more reliable device can be realized through surface engineering via a graphene-ferroelectric device process.
关键词： Surface Roughness,Graphene,Ferroelectric,Interface
更新于2025-09-04 15:30:14
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Preparation, Characterization, and Photocatalytic Activity of LaMnO3 Nanorods-reduced Graphene Oxide Composite
摘要： Background: A new type of photocatalyst with a perovskite structure is recently utilized. The one-dimensional nanostructure of photocatalysts holds great charge mobility along the crystal longitudinal dimension and can hence provide the direct pathways of charge carriers. Graphene holds a superior electrical conductivity and high specific surface area. The aims of this paper are to make LaMnO3 nanorods disperse on the graphene surface. The synergistic effect between graphene and LaMnO3 nanorods enhances the photocatalytic performance. Method: LaMnO3 nanorods–graphene is fabricated using cetyltrimethyl ammonium bromide as template by a simple hydrothermal reaction followed by heat treatment. Results: XRD result indicates that the appropriate calcination temperature for the perovskite structure formation is 650°C. Electron microscopy reveals the LaMnO3 nanorods exhibit a good dispersion behavior on the surface of graphene and the specific surface area of LaMnO3 nanorods-graphene is higher than that of LaMnO3 nanorods. The activities of LaMnO3 nanorods–graphene and TiO2 are compared for degradation of Direct Green BE, the decolorizing rates are 99.93% and 79.45%, respectively. Conclusion: The photocatalytic results for Direct Green BE degradation showed that LaMnO3 nanorods–reduced graphene oxide exhibit a superior photocatalytic performance than that of LaMnO3 nanorods and TiO2 powders. The one-dimensional nanorod structure of LaMnO3 can provide a direct pathway for electronic transmission, and the increased aspect ratio is favorable for reducing the recombination probability of the electron and hole. Meanwhile, the photoelectron transport along the graphene sheets can promote the separation of the e?–h+ pairs.
关键词： Perovskite,nanorods,hydrothermal reaction,composite,photocatalysis,graphene
更新于2025-09-04 15:30:14
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Plasmon confinement by carrier density modulation in graphene
摘要： We investigate plasmon resonances in graphene with periodic carrier density modulation. The period is 8 μm, and each period consists of 1.7- and 6.3-μm-wide ribbons with di?erent density. Using terahertz spectroscopy, we show two plasmon modes with their electric ?eld mostly localized in the 1.7- or 6.3-μm-wide ribbon arrays. We also show that plasmons are excited only in one of the micro-ribbon arrays when the Fermi energy of the other micro-ribbon array is set close to the charge neutrality point. These results indicate that plasmons can be con?ned by the carrier density modulation. ? 2018 The Japan Society of Applied Physics
关键词： carrier density modulation,plasmon resonances,graphene,terahertz spectroscopy
更新于2025-09-04 15:30:14
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Improved Electrical Contact Properties of MoS <sub/>2</sub> -Graphene Lateral Heterostructure
摘要： 2D materials have been extensively investigated in view of their excellent electrical/optical properties, with particular attention directed at the fabrication of vertical or lateral heterostructures. Although such heterostructures exhibit unexpected or enhanced properties compared to those of singly used 2D materials, their fabrication is challenged by the difficulty of realizing spatial control and large area integration. Herein, MoS2 is grown on patterned graphene at variable temperatures, combining the concept of lateral heterostructure with chemical vapor deposition to realize large area growth with precise spatial control, and probe the spatial distribution of graphene and MoS2 by a number of instrumental techniques. The prepared MoS2-graphene lateral heterostructure is employed to construct field effect transistors with graphene as the source/drain and MoS2 as the channel, and the performance of these transistors (on/off ratio ≈109, maximum field effect mobility = 8.5 cm2 V?1 s?1) is shown to exceed that of their MoS2-only counterparts.
关键词： chemical vapor deposition,lateral,heterostructure,contact resistance,MoS2,graphene
更新于2025-09-04 15:30:14
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Preparation of carbon dots decorated graphene/polyaniline composites by supramolecular in-situ self-assembly for high-performance supercapacitors
摘要： Supramolecular in-situ self-assembly is achieved to prepare carbon nanodots decorated graphene/polyaniline composites by adding β-cyclodextrin (β-CD) as the bonding agent in this work. With its unique structure, β-CD can form a supramolecular system with graphene oxide layers, generating the inclusion compound with aniline monomers, which makes the in-situ polymerization of polyaniline on the surface of graphene oxide. In the hydrothermal process, β-CD is carbonized to carbon nanodots anchored on the surface of reduced graphene oxide. The scanning electron microscopy (SEM) images show that the prepared reduced graphene oxide/carbon nanodots/polyaniline (RGO@CN/PANI) nanocomposites exhibit the micro morphology of a regular polyaniline particle array on the surface of graphene layers. The electrochemical tests demonstrate that the RGO@CN/PANI nanocomposites exhibit high specific capacitance (up to 871.8 F g-1 at 0.2A g-1), low charge transfer resistance (Rct), and presentable cycling performance (72% capacitance retention after 10000 cycles), indicating the satisfied performance for supercapacitors. The promising performance of RGO@CN/PANI can be attributed to the synergistic effect of RGO, carbon nanodots and PANI, as well as the regular microstructure in which the effective reaction area of polyaniline is increased and the rapid ion transport channel is provided.
关键词： β-cyclodextrin,supramolecular in situ self-assembly,Carbon dots modified Graphene,polyaniline
更新于2025-09-04 15:30:14
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Enhanced Electrocatalysis via Boosted Separation of Hot Charge Carriers of Plasmonic Gold Nanoparticles Deposited on Reduced Graphene Oxide
摘要： The plasmon enhancement on electrocatalysis was investigated on pure Au nanoparticles (AuNPs) and AuNPs-reduced graphene oxide (AuNPs/rGO) hybrid. Upon Localized surface plasmon resonance (LSPR) excitation, hot charge carriers (hot electrons and holes) generate on AuNPs. In the experiments, hot holes are scavenged by glucose, and hot electrons could be efficiently transferred to the external electric circuit under a potential bias, resulting in an observable current enhancement. Then the hot electrons transfer efficiency can be quantitatively compared by the increased current response. It was found that the current density increases more obviously on AuNPs/rGO hybrid compared to pure AuNPs upon light irradiation. Due to the excellent electron mobility of rGO and perfect electron affinity capacity, the hot electrons generated on AuNPs will be efficiently transferred to the closely contacted rGO, then flow into the external circuit generating current. The present study highlights the role of rGO in improving the separation of hot charge carriers to promote the photocatalysis reactions.
关键词： Au nanoparticles (AuNPs),Hot charge carriers,Localized surface plasmon resonance (LSPR),Graphene,Electrochemical method
更新于2025-09-04 15:30:14
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Photocatalytic activities using a nanocomposite of mesoporous SiO2 and CdInSe-graphene nanoparticles under visible light irradiation
摘要： The new novel ternary mesoporous SiO2/CdInSe-graphene composites with diameters of approximately 8.08 nm have been fabricated through a self-assembly method. All physical tests demonstrated that the CdInSe-graphene was successfully uniformly distributed onto the surface of the ordered mesoporous silica particles. The obtained mesoporous SiO2/CdInSe-graphene composites exhibited good photocatalytic activity for degradation of both cationic-anionic organic dye groups, as well as the decomposition of the representative phenol group of the compound under visible light irradiation. Moreover, the photocatalytic evolution of hydrogen was studied for establishing a wider application of the as-fabricated SiO2/CdInSe-graphene catalyst in the case of energy conversion. This work indicated that the combination of the mesoporous silica and CdInSe-graphene enables achievements such as an enhancement photocatalytic performance, which has potential in industrial waste management and energy conversion.
关键词： Dye decomposition,CdInSe nanoparticles,Graphene-based nanocomposite,Gallic acid degradation,Mesoporous silica,Hydrogen production
更新于2025-09-04 15:30:14
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A tunable ultra-broadband linear-to-circular polarization converter containing the graphene
摘要： In this paper, a tunable ultra-broadband linear-to-circular polarization converter (LCPC) in terahertz regime containing the graphene is proposed, which are composed of two "I"-shaped gold resonators, a strip-shaped graphene sheet, two dielectric layer and a bottom gold reflector. The proposed LCPC can convert the linearly polarized wave into circularly polarized wave in an ultra-broadband frequency range which can be expanded to the lower frequencies by decreasing the Fermi energy (??f ) of the graphene in terahertz region. When ??f = 0.4 eV, 0.6 eV, 0.8 eV and 1.0 eV, the axial ratio band of the proposed LCPC which is less than 3 dB are covered 0.9248～2.2880 THz, 0.9408～2.2893 THz, 0.9665～2.2803 THz, and 0.9746～2.2780 THz, whose relative bandwidths are 84.86%, 83.49%, 80.93% and 80.15%, respectively. The maximum 3 dB axial ratio band is located at 0.9248～2.2880 THz and its relative bandwidth is 84.86% at the case of ??f = 0.4 eV. The polarization conversion rate curves, reflection phase curves, surface current and electric field diagrams are analyzed to elucidate the physical characteristics of the presented LCPC. In addition, the effect of parameters a, b and c on the axial ratio band are also discussed, respectively. This design offers an effective way to realize the reconfigurable LCPC, and also has enormous potential value in realizing the THz devices.
关键词： Graphene,Ultra-broadband,Tunable line-to-circular polarization converter
更新于2025-09-04 15:30:14
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Synthesis of Si-based KH560/RGO@Fe3O4 composite for improving electromagnetic properties in 2–18?GHz frequency range
摘要： Silicon coupling reagent is regarded as a common additive on surface treatment of polymer due to its high bonding strength and low cost. In this paper, a series of γ-(2, 3-epoxypropoxy) propyltrimethoxysilane (KH560)-based reduced graphene oxide (RGO)@Fe3O4 (KH560/RGO@Fe3O4) composites with different ratio of Fe3O4 nanoparticles (NPs) are synthesized by a facile hydrothermal method. It is confirmed that the silicon reagent KH560, as a hopeful candidate for increasing the RGO lattice defects, is favorable to improve the electromagnetic wave absorption. Meanwhile, the microwave attenuation mechanism of KH560/RGO@Fe3O4 composite suggests that the dielectric loss mainly causes by multiple Debye dipolar relaxation and its magnetic loss comes from the eddy-current effect of Fe3O4 NPs over the high frequency range. In consequence, the KH560/RGO@Fe3O4 composite endows the excellent absorption performance, the reflection loss (RL) value is optimized to ? 25 dB at 14.1 GHz with a thickness of 3 mm and the maximum frequency bandwidth for RL < ? 10 dB is 4.1 GHz with a thickness of 4 mm.
关键词： Electromagnetic wave absorption,Fe3O4 nanoparticles,Reduced graphene oxide,Hydrothermal method,Silicon coupling reagent
更新于2025-09-04 15:30:14
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Carbohydrate Functionalization of Few-Layer Graphene through Microwave-Assisted Reaction of Perfluorophenyl Azide
摘要： The excellent physical and chemical properties of graphene make it an attractive nanomaterial and a component in high-performance nanocomposite materials. To prepare graphene-based nanocomposite materials, the chemical functionalization is often necessary. Water-soluble ligands such as carbohydrates not only make the functionalized graphene compatible with aqueous media, but also introduce bio-recognition which is important for graphene to be used in biotechnology. In this study, we report the derivatization of few-layer graphene (FLG) with carbohydrates through microwave-assisted reaction of perfluorophenyl azide (PFPA). FLG was first treated with PFPA under microwave radiation. Subsequent conjugation with glycosyl amine gave carbohydrate-presenting FLG. Thermogravimetric analysis showed that microwave radiation gave a higher degree of functionalization compared to conventional heating, with higher weight losses for both PFPA and Man ligands. The carbohydrates (mannose and galactose) retained their bioactivity, as demonstrated by the lectin binding assays. Higher degree of binding towards lectins was obtained for the carbohydrate-functionalized FLG prepared by microwave radiation than the conventional heating.
关键词： microwave radiation,perfluorophenyl azide,graphene,carbohydrate,lectin
更新于2025-09-04 15:30:14