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Preparation of graphene nanoribbons (GNRs) from twisted structure carbon nanotubes using unzipping technique
摘要： This work deals with the preparation of graphene nano ribbons (GNRs), which are small bars or strips of graphene with narrow range width less than 50 nm and one atom thick sheet (approximately 140 °A). This material has many applications in electronics, polymer composite, contrast agent bio-imaging and others. This material was prepared from twisted structure of carbon nanotubes CNTs using oxidation process by acids and breaking down by high frequency ultrasonication (sonochemical unzipping). Pre-prepared twisted CNTs were characterized by scanning electron microscope (HRSEM) before treatment. The size, morphology, crystallinity of prepared graphene nanoribbons was also investigated using transmission electron microscope, high resolution transmission electron microscope, and X-ray diffraction and particle size analyzer. The results showed of formation of GNRs with narrow width as lower than 29 nm and uniform sizes. X-ray diffraction reveals Bragg reflections corresponding to the lattice planes (002), (100), (101), (004), and (110) matched with hexagonal system of graphite.
关键词： sonochemical unzipping,Twisted carbon nanotubes,graphene nanoribbons
更新于2025-09-23 15:23:52
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Edge-dependent reflection and inherited fine structure of higher-order plasmons in graphene nanoribbons
摘要： We investigate higher-order plasmons in graphene nanoribbons, and we present how electronic edge states and wave-function fine structure influence the graphene plasmons. Based on nearest-neighbor tight-binding calculations, we find that a standing-wave model based on nonlocal bulk plasmon dispersion is surprisingly accurate for armchair ribbons of widths even down to a few nanometers, and we determine the corresponding phase shift upon edge reflection and an effective ribbon width. Wider zigzag ribbons exhibit a similar phase shift, whereas the standing-wave model describes few-nanometer zigzag ribbons less satisfactorily, to a large extent because of their edge states. We directly confirm that also the larger broadening of plasmons for zigzag ribbons is due to their edge states. Furthermore, we report a prominent fine structure in the induced charges of the ribbon plasmons, which for armchair ribbons follows the electronic wave-function oscillations induced by intervalley coupling. Interestingly, the wave-function fine structure is also found in our analogous density-functional theory calculations, and both these and tight-binding numerical calculations are explained quite well with analytical Dirac theory for graphene ribbons.
关键词： plasmons,edge states,tight-binding,density-functional theory,Dirac theory,graphene nanoribbons
更新于2025-09-23 15:23:52
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Femtosecond Electron Dynamics in Graphene Nanoribbons - A Nonequilibrium Green Functions Approach Within an Extended Hubbard Model
摘要： A new approach to study the correlated femtosecond electron dynamics in finite graphene clusters, such as nanoribbons, is presented here. The systems are described by an extended Hubbard model that takes into account the overlap of adjacent orbitals and hopping between up to third-nearest neighbors. The model is solved by the nonequilibrium Green functions approach combined with different self-energy approximations, including the second-Born and GW self-energy, to take into account electronic correlations. The description allows us to predict the correlated nonequilibrium dynamics of excited graphene nanostructures of arbitrary geometry containing up to 100 carbon atoms for up to 25 fs.
关键词： correlated dynamics,nonequilibrium Green functions,Hubbard model,graphene nanoribbons
更新于2025-09-23 15:23:52
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Transport properties of doped zigzag graphene nanoribbons
摘要： Numerous studies on materials have driven the development of modern nanoelectronic devices. And research also shown that the integrated circuits have entered the era of the nanoelectronic scales from the scale of microelectronics. But the limitations of copper as a traditional connection, such as the resistivity increases a lot, further causing a lot of heat in the interconnect, have been highlighted. Therefore, we need new materials as the substitution of copper. The metallic properties exhibited by the zigzag graphene nanoribbons (ZGNRs) can be controlled by the edge states, doping and different widths of the nanoribbons. In this paper, we applied simulation to dope copper atom chains on ZGNRs. We found an energetic phenomenon that after doping the nanoribbons conductivity have increased significantly than the original. In addition, the transmission channels are mainly concentrated near the doping position, and the width used for transmission is greatly reduced after doping. It is expected to be used as an inter-connect application in nano-integrated circuits in the future.
关键词： Density functional theory,Interconnect,Electronic transport property,Non-equilibrium Green's function,Zigzag graphene nanoribbons,Doping
更新于2025-09-23 15:23:52
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Toward Longer Phenacenes
摘要： Toward Longer Phenacenes. Polyacene and polyphenacene represent the simplest graphene nanoribbons, but whereas acenes are unstable beyond seven units, longer phenacenes have been successfully synthesized. The authors describe the synthesis of tetracarboxy- and imide-functionalized [8]-, [10]-, [12]-, and [14]phenacenes, the longest reported to date. Comment: Perkin condensation of the appropriate arylene diglyoxylic acids and arylacetic acids, followed by esterification, furnishes the bismaleates, which are converted into the phenacenes by oxidative photocyclization. Optical and electrochemical properties are studied, with the imides exhibiting significantly lower band gaps than the esters.
关键词： phenacenes,graphene nanoribbons,polycyclic aromatic hydrocarbons
更新于2025-09-23 15:21:21
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1D ballistic transport channel probed by invasive and non-invasive contacts
摘要： Epitaxially grown sidewall graphene nanoribbons show a robust quantum conductance of e2/h. By means of in-situ transport measurements with a nanoprobe system, we realized invasive and non-invasive 4-point-probe configurations. The invasiveness correlates with the contact resistance of the voltage probes. In particular, we achieved now non-invasive voltage probes revealing an almost zero resistance in a collinear 4 point-probe measurement. This proofs the ballistic nature of our epitaxially grown sidewall nanoribbons on SiC(0001) mesa structures.
关键词： quantum conductance,graphene nanoribbons,ballistic transport,non-invasive contacts,invasive contacts
更新于2025-09-23 15:21:21
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Electronic structure of graphene nanoribbons on hexagonal boron nitride
摘要： Hexagonal boron nitride is an ideal dielectric to form two-dimensional heterostructures due to the fact that it can be exfoliated to be just a few atoms thick and its very low density of defects. By placing graphene nanoribbons on high quality hexagonal boron nitride it is possible to create ideal quasi-one-dimensional systems with very high mobility. The availability of high quality one-dimensional electronic systems is of great interest also given that when in proximity to a superconductor they can be effectively engineered to realize Majorana bound states. In this work we study how a boron nitride substrate affects the electronic properties of graphene nanoribbons. We consider both armchair and zigzag nanoribbons. Our results show that for some stacking configurations the boron nitride can significantly affect the electronic structure of the ribbons. In particular, for zigzag nanoribbons, due to the lock between spin and sublattice degree of freedom at the edges, the hexagonal boron nitride can induce a very strong spin splitting of the spin-polarized, edge states. We find that such spin splitting can be as high as 40 meV.
关键词： heterostructures,graphene nanoribbons,hexagonal boron nitride,spin splitting,electronic structure
更新于2025-09-23 15:21:21
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Controlled Quantum-Dot Formation in Atomically-Engineered Graphene Nanoribbons Field-Effect Transistors
摘要： Graphene nanoribbons (GNRs) have attracted a strong interest from researchers worldwide, as they constitute an emerging class of quantum-designed materials. The major challenges towards their exploitation in electronic applications include reliable contacting, complicated by their small size (< 50 nm), as well as the preservation of their physical properties upon device integration. In this combined experimental and theoretical study, we report on the quantum dot (QD) behavior of atomically precise GNRs integrated in a device geometry. The devices consist of a film of aligned 5-atoms wide GNRs (5-AGNRs) transferred onto graphene electrodes with a sub 5-nm nanogap. We demonstrate that the narrow-bandgap 5-AGNRs exhibit metal-like behavior at room temperature and single-electron transistor behavior for temperatures below 150 K. By performing spectroscopy of the molecular levels at 13 K, we obtain addition energies in the range of 200-300 meV. DFT calculations predict comparable addition energies and reveal the presence of two electronic states within the bandgap of infinite ribbons when the finite length of the 5-AGNRs is accounted for. By demonstrating the preservation of the 5-AGNRs molecular levels upon device integration, as demonstrated by transport spectroscopy, our study provides a critical step forward in the realisation of more exotic GNR-based nano-electronic devices.
关键词： graphene nanoribbons,Coulomb blockade,molecular spectroscopy,device integration,Raman spectroscopy
更新于2025-09-23 15:21:01
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Substrate-Controlled Synthesis of 5-Armchair Graphene Nanoribbons
摘要： 5-Armchair graphene nanoribbons (5-AGNRs) have been successfully synthesized through on-surface reaction of 1, 4, 5, 8-tetrabromonaphthalene (TBN) on Ag(111) and characterized by scanning tunneling microscopy. Silver-naphthalene chains are observed as intermediate states toward the formation of 5-AGNRs. Similar reaction of TBN has been conducted on Cu(111), but no 5-AGNRs are obtained. Disordered amorphous products prevail on Cu(111) upon high temperature annealing (600 K), which is tentatively explained by the strong aryl-Cu bonds. Scanning tunneling spectroscopy measurements of 5-AGNRs on Ag(111) reveal three prominent peaks at bias voltages of -0.3, 1.0 and 1.5V, determining that the apparent band gap is 1.3 eV.
关键词： Ag(111),scanning tunneling microscopy,scanning tunneling spectroscopy,5-Armchair graphene nanoribbons,Cu(111),on-surface synthesis
更新于2025-09-23 15:21:01
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Effects of different tailoring graphene electrodes on the rectification and negative differential resistance of molecular devices
摘要： The electronic transport properties of oligo p-phenylenevinylene (OPV) molecule sandwiched with symmetrical or asymmetric tailoring graphene nanoribbons (GNRs) electrodes are investigated by nonequilibrium Green’s function in combination with density functional theory. The results show that different tailored GNRs electrodes can modulate the current–voltage characteristic of molecular devices. The rectifying behavior can be observed with respect to electrodes, and the maximum rectification ratio can reach to 14.2 in the asymmetric AC–ZZ GNRs and ZZ–AC–ZZ GNRs electrodes system. In addition, the obvious negative differential resistance can be observed in the symmetrical AC-ZZ GNRs system.
关键词： negative differential resistance,Graphene nanoribbons electrodes,nonequilibrium Green’s function method,rectifying behavior
更新于2025-09-23 15:21:01