Quantum Dots in Graphene Nanoribbons

Abstract

Graphene quantum dots (GQDs) hold great promise for applications in electronics, optoelectronics, and bioelectronics, but the fabrication of widely tunable GQDs has remained elusive. Here, we report the fabrication of atomically precise GQDs consisting of low-bandgap N = 14 armchair graphene nanoribbon (AGNR) segments that are achieved through edge fusion of N = 7 AGNRs. The so-formed intraribbon GQDs reveal deterministically defined, atomically sharp interfaces between wide and narrow AGNR segments and host a pair of low-lying interface states. Scanning tunneling microscopy/spectroscopy measurements complemented by extensive simulations reveal that their energy splitting depends exponentially on the length of the central narrow bandgap segment. This allows tuning of the fundamental gap of the GQDs over 1 order of magnitude within a few nanometers length range. These results are expected to pave the way for the development of widely tunable intraribbon GQD-based devices.

Electrical spin manipulation in graphene nanostructures

“…This has been established using either density functional theory (DFT) and/or mean field Hubbard model calculations in the case of infinitely long graphene ribbons with zigzag edges [24,35] as well as the small nanoribbons considered here [18,40] and for hydrogenated graphene [26,30,38,50]. The emergence of local moments in the case of undoped topological junctions is explored here.…”

“…The exploration with STM of some of the graphene nanostructures studied here has been demonstrated [17,18,30]. With this approach, the application of an off-plane electric field significantly larger than in conventional field effect transistor geometries is possible.…”

“…Interestingly, a class of graphene nanostructures that can be synthesized with bottom-up techniques [17,18] provides naturally, without the need of electrical control of the number of carriers, exchange-coupled unpaired spin electron duets in an environment with a low density of carbon nuclear spins. In Fig.…”

“…1(b). Recent progress in the fabrication of graphene ribbon heterojunctions [18,40] shows that fabrication of this type of structure is not out of reach of the state of the art in nanographene synthesis.…”

Design of Atomically Precise Nanoscale Negative Differential Resistance Devices

“…[2][3][4][5][6][7][8][9][10][11][12][13] The recent development of graphene and graphene nanoribbons (GNRs) offers new opportunities to design nanoscale devices and to test NDR at the atomic scale. [15][16][17][18][19][20][21][22][23] In particular, controllable polymer-to-GNR conversion reaction was demonstrated using charge injection from a scanning tunneling microscope (STM) tip. [15][16][17][18][19][20][21][22][23] In particular, controllable polymer-to-GNR conversion reaction was demonstrated using charge injection from a scanning tunneling microscope (STM) tip.…”