Width-Dependent Band Gap in Armchair Graphene Nanoribbons Reveals Fermi Level Pinning on Au(111)
نویسندگان
چکیده
We report the energy level alignment evolution of valence and conduction bands of armchair-oriented graphene nanoribbons (aGNR) as their band gap shrinks with increasing width. We use 4,4″-dibromo-para-terphenyl as the molecular precursor on Au(111) to form extended poly-para-phenylene nanowires, which can subsequently be fused sideways to form atomically precise aGNRs of varying widths. We measure the frontier bands by means of scanning tunneling spectroscopy, corroborating that the nanoribbon's band gap is inversely proportional to their width. Interestingly, valence bands are found to show Fermi level pinning as the band gap decreases below a threshold value around 1.7 eV. Such behavior is of critical importance to understand the properties of potential contacts in GNR-based devices. Our measurements further reveal a particularly interesting system for studying Fermi level pinning by modifying an adsorbate's band gap while maintaining an almost unchanged interface chemistry defined by substrate and adsorbate.
منابع مشابه
On-surface synthesis of rylene-type graphene nanoribbons.
The narrowest armchair graphene nanoribbon (AGNR) with five carbons across the width of the GNR (5-AGNR) was synthesized on Au(111) surfaces via sequential dehalogenation processes in a mild condition by using 1,4,5,8-tetrabromonaphthalene as the molecular precursor. Gold-organic hybrids were observed by using high-resolution scanning tunneling microscopy and considered as intermediate states u...
متن کاملElectronic properties of hydrogenated porous Graphene based nanoribbons: A density functional theory study
The structural and electronic properties of the hydrogenated porous graphene nanoribbons were studied by using density functional theory calculations. The results show that the hydrogenated porous graphene nanoribbons are energetically stable. The effects of ribbon type and ribbon width on the electronic properties of these nanoribbons were investigated. It was found that both armchair and zigz...
متن کاملElectronic and Optical Properties of the Graphene and Boron Nitride Nanoribbons in Presence of the Electric Field
Abstract: In this study, using density functional theory and the SIESTA computationalcode, we investigate the electronic and optical properties of the armchair graphenenanoribbons and the armchair boron nitride nanoribbons of width 25 in the presence of atransverse external electric field. We have observed that in the absence of the electricfield, these structures are se...
متن کاملEffect of Substrate on Bottom- Up Fabrication and Electronic Properties of Graphene Nanoribbons
Simonov, K. 2016. Effect of Substrate on Bottom-Up Fabrication and Electronic Properties of Graphene Nanoribbons. Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 1385. 101 pp. Uppsala: Acta Universitatis Upsaliensis. ISBN 978-91-554-9610-4. Taking into account the technological demand for the controlled preparation of atomically precise graphe...
متن کاملElectronic structure changes during the surface-assisted formation of a graphene nanoribbon.
High conductivity and a tunability of the band gap make quasi-one-dimensional graphene nanoribbons (GNRs) highly interesting materials for the use in field effect transistors. Especially bottom-up fabricated GNRs possess well-defined edges which is important for the electronic structure and accordingly the band gap. In this study we investigate the formation of a sub-nanometer wide armchair GNR...
متن کامل