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Light absorption and pseudospin density generation in graphene nanoribbons
摘要： Light absorption in graphene nanoribbons is studied analytically and numerically. Due to size quantization, the electronic states in the nanoribbon form a set of one-dimensional subbands modifying remarkably the absorption coefficient. The electronic subbands are calculated using the Berry-Mondragon boundary conditions at the nanoribbon edges, which are applicable for nanoribbons of the armchair type. Numerical results on pseudospin (sublattice) density generation by light absorption are presented and discussed.
关键词： pseudospin density,graphene nanoribbons,light absorption,Berry-Mondragon boundary conditions,armchair type
更新于2025-09-23 15:19:57
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Solution and on-surface synthesis of structurally defined graphene nanoribbons as a new family of semiconductors
摘要： Graphene nanoribbons (GNRs) are quasi-one-dimensional subunits of graphene and have open bandgaps in contrast to the zero-bandgap graphene. The high potential of GNRs as a new family of carbon-based semiconductors, e.g. for nanoelectronic and optoelectronic applications, has boosted the research attempts towards fabrication of GNRs. The predominant top-down methods such as lithographical patterning of graphene and unzipping of carbon nanotubes cannot prevent defect formation. In contrast, bottom-up chemical synthesis, starting from tailor-made molecular precursors, can achieve atomically precise GNRs. In this account, we summarize our recent research progress in the bottom-up synthesis of GNRs through three different methods, namely (1) in solution, (2) on-surface under ultrahigh vacuum (UHV) conditions, and (3) on-surface through chemical vapour deposition (CVD). The solution synthesis allows fabrication of long (>600 nm) and liquid-phase-processable GNRs that can also be functionalized at the edges. On the other hand, the on-surface synthesis under UHV enables formation of zigzag GNRs and in situ visualization of their chemical structures by atomic-resolution scanning probe microscopy. While the on-surface synthesis under UHV is typically costly and has limited scalability, the industrially viable CVD method can allow lower-cost production of large GNR films. We compare the three methods in terms of the affordable GNR structures and the resulting control of their electronic and optical properties together with post-processing for device integration. Further, we provide our views on future perspectives in the field of bottom-up GNRs.
关键词： semiconductors,CVD,on-surface synthesis,UHV,Graphene nanoribbons,optoelectronics,bottom-up synthesis,solution synthesis
更新于2025-09-19 17:15:36
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[Communications in Computer and Information Science] VLSI Design and Test Volume 892 (22nd International Symposium, VDAT 2018, Madurai, India, June 28-30, 2018, Revised Selected Papers) || Performance Analysis of Graphene Based Optical Interconnect at Nanoscale Technology
摘要： In the modern technology era, interconnect is the key element for designing integrated circuits that provides on-chip and off-chip communication path for various systems. The primary challenges for modeling interconnect are reduced propagation delay, power dissipation, and its power delay product at advanced technology. This paper critically addresses the performance of optical interconnects using equivalent electrical model that comprises of different composite materials. Using industry standard HSPICE, the propagation delay and power dissipation characteristics of graphene nanoribbon have been compared with other composite materials. It has been observed that the propagation delay for graphene nanoribbon can be improved by 99.91% as compared to other composite materials. The power delay product of the proposed graphene based interconnect model is 59.73% lesser compared to other composite materials at 22 nm technology node.
关键词： Power delay product (PDP),Graphene nanoribbons,Propagation delay,Optical interconnect,Power dissipation
更新于2025-09-19 17:15:36
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Plasmonic Gas Sensing with Graphene Nanoribbons
摘要： The main challenge to exploiting plasmons for gas vibrational mode sensing is the extremely weak infrared absorption of gas species. In this work, we explore the possibility of trapping free-gas molecules via surface adsorption, optical, or electrostatic fields to enhance gas-plasmon interactions and to increase plasmon-sensing ability. We discuss the relative strengths of these trapping forces and find gas adsorption in a typical nanoribbon array plasmonic setup produces measurable dips in optical extinction of magnitude 0.1% for a gas concentration of about the parts per thousand level.
关键词： Optical extinction,Infrared absorption,Graphene nanoribbons,Gas-plasmon interactions,Plasmonic gas sensing
更新于2025-09-19 17:13:59
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The detection of sub-terahertz radiation using graphene-layer and graphene-nanoribbon FETs with asymmetric contacts
摘要： We report on the detection of sub-terahertz radiation using single layer graphene and graphene-nanoribbon FETs with asymmetric contacts (one is the Schottky contact and one – the Ohmic contact). We found that cutting graphene into ribbons a hundred nanometers wide leads to a decrease of the response to sub-THz radiation. We show that suppression of the response in the graphene nanoribbons devices can be explained by unusual properties of the Schottky barrier on graphene-vanadium interface.
关键词： detector,THz region,graphene,terahertz radiation,graphene nanoribbons,optoelectronics
更新于2025-09-16 10:30:52
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Transport in armchair graphene nanoribbons and in ordinary waveguides
摘要： We study dc and ac transport along armchair graphene nanoribbons using the k (cid:1) p spectrum and eigenfunctions and general linear-response expressions for the conductivities. Then, we contrast the results with those for transport along ordinary waveguides. In all cases, we assess the influence of elastic scattering by impurities, describe it quantitatively with a Drude-type contribution to the current previously not reported, and evaluate the corresponding relaxation time for long- and short-range impurity potentials. We show that this contribution dominates the response at very low frequencies. In both cases, the conductivities increase with the electron density and show cusps when new subbands start being occupied. As functions of the frequency, the conductivities in armchair graphene nanoribbons exhibit a much richer peak structure than in ordinary waveguides: in the former, intraband and interband transitions are allowed, whereas in the latter, only the intraband ones occur. This difference can be traced to that between the corresponding spectra and eigenfunctions.
关键词： transport,elastic scattering,armchair graphene nanoribbons,intraband and interband transitions,conductivities,relaxation time,Drude-type contribution
更新于2025-09-11 14:15:04
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Exploration of Interfacial Porphine Coupling Schemes and Hybrid Systems by Bond-Resolved Scanning Probe Microscopy
摘要： The templated synthesis of porphyrin-based oligomers and heterosystems is of considerable interest for materials with tunable electronic gaps, photovoltaics, or sensing device elements. In this work, temperature-induced dehydrogenative coupling between unsubstituted free-base porphine units and their attachment to graphene nanoribbons on a well-defined Ag(111) support are scrutinized by bond-resolved scanning probe microscopy techniques. The detailed inspection of covalently fused porphine dimers obtained by in vacuo on-surface synthesis clearly reveals atomistic details of coupling motifs, whereby also putative reaction intermediates are identified. Moreover, the covalent attachment of porphines at preferred locations of atomically precise armchair-type graphene nanoribbons is demonstrated.
关键词： porphyrins,graphene nanoribbons,scanning probe microscopy,surface chemistry,C–C coupling
更新于2025-09-10 09:29:36
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Exploration of Interfacial Porphine Coupling Schemes and Hybrid Systems by Bond-Resolved Scanning Probe Microscopy
摘要： The templated synthesis of porphyrin-based oligomers and heterosystems is of considerable interest for materials with tunable electronic gaps, photovoltaics, or sensing device elements. In this work, temperature-induced dehydrogenative coupling between unsubstituted free-base porphine units and their attachment to graphene nanoribbons on a well-defined Ag(111) support are scrutinized by bond-resolved scanning probe microscopy techniques. The detailed inspection of covalently fused porphine dimers obtained by in vacuo on-surface synthesis clearly reveals atomistic details of coupling motifs, whereby also putative reaction intermediates are identified. Moreover, the covalent attachment of porphines at preferred locations of atomically precise armchair-type graphene nanoribbons is demonstrated.
关键词： porphyrins,graphene nanoribbons,scanning probe microscopy,surface chemistry,C–C coupling
更新于2025-09-10 09:29:36
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Termini effects on the optical properties of graphene nanoribbons
摘要： We investigate from first principles the optical response of finite-length armchair-edged graphene nanoribbons (AGNRs) within the framework of many-body perturbation theory. As a result of the explicit inclusion of zigzag extremities, we identify low-energy and low-intensity excitations that are expected to be almost independent of the GNR length. These excitations coexist with bulk-like excitations, which have the same origin as the ones characterizing infinite AGNRs. Our results are used to rationalize termini effects on the optical response of GNRs and to shed light on recent photoluminescence data.
关键词： graphene nanoribbons,optical properties,photoluminescence,many-body perturbation theory,zigzag extremities
更新于2025-09-10 09:29:36
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Strain engineering of chevron graphene nanoribbons
摘要： In this work, we theoretically investigate the material and transport properties of strained chevron graphene nanoribbons (CGNRs) which can be easily synthesized by the bottom-up fabrication technology. Because of the unique atomic structures, the energy and pressure of the CGNRs vary asymmetrically along compressive and tensile strains. Under the two strain directions, the CGNRs’ bandgaps and carrier effective masses in the conduction band minimum and the valence band maximum are all reduced. The transport properties are promoted accordingly, except some negative differential conductance behaviors caused by energy state localizations. When the tensile strains exceed a criterion value, the C–C bonds in the inner sides of the CGNR corners will be broken in sequence. Meanwhile, the CGNRs can restore their initial unstrained states rapidly when the strains are removed. However, if the broken bonds are saturated by foreign atoms, such as H, a novel kind of stable carbon structure will be obtained. The investigations suggest possible applications of strain engineered CGNRs in transport devices.
关键词： carrier effective masses,strain engineering,transport properties,chevron graphene nanoribbons,bandgap
更新于2025-09-04 15:30:14