Morphological characterization and electronic properties of pristine and oxygen-exposed graphene nanoribbons on Ag(110) (original) (raw)
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New Approaches to Edge-Doping Graphene Nanoribbons
Bulletin of the American Physical Society, 2016
TEAM 1 , FISCHER TEAM 2 , LOUIE TEAM 3-Graphene nanoribbons (GNRs) are narrow semiconducting strips of graphene that exhibit novel electronic and magnetic properties. New bottom-up fabrication techniques enable atomic-scale precision in GNR synthesis. The use of these techniques to reliably tune the position and size of GNR band gaps is an important challenge that also has relevance for the question of whether GNRs are viable for future nanotechnologies. We have used scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) to investigate how the geometry of heteroatom incorporation alters the electronic structure of bottom-up fabricated chevron-type GNRs. We find that the addition of nitrogen into the GNR edge via a five-membered ring yields a reduced band gap compared to the behavior of pristine, undoped chevron GNRs.
Superlattices and Microstructures, 2018
Graphene nanoribbon (GNR), a new 2D carbon nanomaterial, has some unique features and special properties that offer a great potential for interconnect, nanoelectronic devices, optoelectronics, and nanophotonics. This paper reports the structural analysis, electronic properties, and band gaps of a GNR considering different chirality combinations obtained using the p z orbital tight binding model. In structural analysis, the analytical expressions for GNRs have been developed and verified using the simulation for the first time. It has been found that the total number of unit cells and carbon atoms within an overall unit cell and molecular structure of a GNR have been changed with the change in their chirality values which are similar to the values calculated using the developed analytical expressions thus validating both the simulation as well as analytical results. Further, the electronic band structures at different chirality values have been shown for the identification of metallic and semiconductor properties of a GNR. It has been concluded that all zigzag edge GNRs are metallic with very small band gaps range whereas all armchair GNRs show both the metallic and semiconductor nature with very small and high band gaps range. Again, the total number of subbands in each electronic band structure is equal to the total number of carbon atoms present in overall unit cell of the corresponding GNR. The semiconductors GNRs can be used as a channel material in field effect transistor suitable for advanced CMOS technology whereas the metallic GNRs could be used for interconnect.
Emergence of Atypical Properties in Assembled Graphene Nanoribbons
Physical Review Letters, 2011
Graphitic nanowiggles are periodic repetitions of non-aligned finite-sized graphitic nanoribbon domains seamlessly stitched together without structural defects. These complex nanostructures have been recently fabricated (Cai et al, Nature 466, 470 (2010)) and are here predicted to possess unusual properties, such as tunable bandgaps and versatile magnetic behaviors. We used first-principles theory to highlight the microscopic origin of the emerging electronic and magnetic properties of the main subclasses of GNWs. Our study establishes a road-map for guiding the design and synthesis of specific GNWs for nanoelectronic, optoelectronic, and spintronic applications.
Analysis of Graphene Nanoribbons Passivated with Gold, Copper and Indium
International Journal of Theoretical and Applied Nanotechnology, 2013
This study investigates the effect of edgepassivation on graphene nanoribbons. The geometry of graphene is simple and regular, and infinite, planar structure can easily be created either by hand or by taking a single layer from the crystal structure of graphene. To create a device-like structure, the infinite sheet must be cut into a suitable shape. Such a shape, at least for electronic applications, and it is called graphene nanoribbon (GNR). A pristine graphene monolayer can be cut into elongated strips to form 1D structure, referred to as graphene nanoribbons (GNRs) which can be either metallic or semiconducting depending on the type and width of edges. On the base of series of simulations it is found that elements from I st , III rd and IV th group are used as passivated elements with Armchair and Zigzag nanoribbons instead of Hydrogen. Best characteristics for zigzag nanoribbons are presented by elements from I st group. All experiments are made with Gold and Copper. For armchair nanoribbons, best characteristic are shown by elements from III rd group. The experiment is made with Indium. For nanoribbon with zigzag shaped edge is used DFT (Density Functional Theory) with LDA (Local Density Approximation). The chiral index of such nanoribbon is (3, 3). For the calculations of armchair nanoribbon is used Extended Hückel method. The chiral index of such nanoribbon is (3, 0). In both cases the k-point are set to 1 x 1 x 100 for na, nb and nc, respectively. For nanoribbons with zigzag shaped edges, DFT calculations show that edge-state bands at Fermi level (EF) rise to a very large Density of States (DOS) at EF, while Density of States of the armchair nanoribbons shows an energy gap around Fermi level. After Band Structure and Density of State, Bloch State is calculated and plot. Bloch States can be used to investigate the symmetry of certain bands and how this may be releated to the transport properties. Looking at the respective Bloch function, the wave function at G and Z are real and there is a distinct difference between valence and conduction band Bloch functions. These findings can be useful for the prospective GNR-based devices.
Direct oriented growth of armchair graphene nanoribbons on germanium
Nature Communications, 2015
Graphene can be transformed from a semimetal into a semiconductor if it is confined into nanoribbons narrower than 10 nm with controlled crystallographic orientation and welldefined armchair edges. However, the scalable synthesis of nanoribbons with this precision directly on insulating or semiconducting substrates has not been possible. Here we demonstrate the synthesis of graphene nanoribbons on Ge(001) via chemical vapour deposition. The nanoribbons are self-aligning 3°from the Geh110i directions, are self-defining with predominantly smooth armchair edges, and have tunable width to o10 nm and aspect ratio to 470. In order to realize highly anisotropic ribbons, it is critical to operate in a regime in which the growth rate in the width direction is especially slow, o5 nm h À 1. This directional and anisotropic growth enables nanoribbon fabrication directly on conventional semiconductor wafer platforms and, therefore, promises to allow the integration of nanoribbons into future hybrid integrated circuits.
Physical Review B, 2012
Angle-resolved two-photon photoemission and high-resolution electron energy loss spectroscopy are employed to derive the electronic structure of a subnanometer atomically precise quasi-one-dimensional graphene nanoribbon (GNR) on Au(111). We resolved occupied and unoccupied electronic bands including their dispersion and determined the band gap, which possesses an unexpectedly large value of 5.1 eV. Supported by density functional theory calculations for the idealized infinite polymer and finite size oligomers, an unoccupied nondispersive electronic state with an energetic position in the middle of the band gap of the GNR could be identified. This state resides at both ends of the ribbon (end state) and is only found in the finite sized systems, i.e., the oligomers.