Abstract
Electrical contact to low-dimensional (low-D) materials is a key to their electronic applications. Traditional metal contacts to low-D semiconductors typically create gap states that can pin the Fermi level (EF). However, low-D metals possessing a limited density of states at EF can enable gate-tunable work functions and contact barriers. Moreover, a seamless contact with native bonds at the interface, without localized interfacial states, can serve as an optimal electrode. To realize such a seamless contact, one needs to develop atomically precise heterojunctions from the atom up. Here, we demonstrate an all-carbon staircase contact to ultranarrow armchair graphene nanoribbons (aGNRs). The coherent heterostructures of width-variable aGNRs, consisting of 7, 14, 21, and up to 56 carbon atoms across the width, are synthesized by a surface-assisted self-assembly process with a single molecular precursor. The aGNRs exhibit characteristic vibrational modes in Raman spectroscopy. A combined scanning tunneling microscopy and density functional theory study reveals the native covalent-bond nature and quasi-metallic contact characteristics of the interfaces. Our electronic measurements of such seamless GNR staircase constitute a promising first step toward making low resistance contacts.
Original language | English |
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Pages (from-to) | 6241-6247 |
Number of pages | 7 |
Journal | Nano Letters |
Volume | 17 |
Issue number | 10 |
DOIs | |
State | Published - Oct 11 2017 |
Funding
This research was conducted at the Center for Nanophase Materials Sciences (CNMS), which is a DOE Office of Science User Facility. The electronic characterization was funded by ONR grants N00014-16-1-3213 and N00014-16-1-3153. The simulation work at NCSU was supported by DOE DE-FG02-98ER45685. The supercomputer time was provided by NSF grant ACI-1615114 at the National Center for Supercomputing Applications (NSF OCI-0725070 and ACI-1238993) and by DOE at the Oak Ridge Leadership Computing Facility and at the National Energy Research Scientific Computing Center. L.L. was supported by Eugene P. Wigner Fellowship at the Oak Ridge National Laboratory and by the Center for Nanophase Materials Sciences. Parts of phonon calculations were performed using the resources of the Center for Computational Innovation at Rensselaer Polytechnic Institute.
Keywords
- Electrical contact
- graphene nanoribbon
- heterostructure
- scanning tunneling microscopy
- staircase
- vibrational modes