| 1. |
- Aprojanz, Johannes, et al.
(författare)
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Ballistic tracks in graphene nanoribbons
- 2018
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- High quality graphene nanoribbons epitaxially grown on the sidewalls of silicon carbide (SiC) mesa structures stand as key building blocks for graphene-based nanoelectronics. Such ribbons display 1D single-channel ballistic transport at room temperature with exceptionally long mean free paths. Here, using spatially-resolved two-point probe (2PP) measurements, we selectively access and directly image a range of individual transport modes in sidewall ribbons. The signature of the independently contacted channels is a sequence of quantised conductance plateaus for different probe positions. These result from an interplay between edge magnetism and asymmetric terminations at opposite ribbon edges due to the underlying SiC structure morphology. Our findings demonstrate a precise control of transport through multiple, independent, ballistic tracks in graphene-based devices, opening intriguing pathways for quantum information device concepts.
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| 2. |
- Aprojanz, Johannes, et al.
(författare)
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Nanoscale imaging of electric pathways in epitaxial graphene nanoribbons
- 2019
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Ingår i: Nano Research. - : Springer Science and Business Media LLC. - 1998-0124 .- 1998-0000. ; 12:7, s. 1697-1702
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Tidskriftsartikel (refereegranskat)abstract
- Graphene nanoribbons (GNRs) are considered as major building blocks in future carbon-based electronics. The electronic performance of graphene nanostructures is essentially influenced and determined by their edge termination and their supporting substrate. In particular, semi-conducting, as well as metallic GNRs, can be fabricated by choosing the proper template which is favorable for device architecture designs. This study highlights the impact of microscopic details of the environment of the GNRs on the charge transport in GNRs. By means of lateral force, conductive atomic force and nanoprobe measurements, we explore the charge propagation in both zig-zag and armchair GNRs epitaxially grown on SiC templates. We directly image transport channels on the nanoscale and identify SiC substrate steps and nano-instabilities of SiC facets as dominant charge scattering centers. [Figure not available: see fulltext.].
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| 3. |
- Karakachian, Hrag, et al.
(författare)
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One-dimensional confinement and width-dependent bandgap formation in epitaxial graphene nanoribbons
- 2020
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Ingår i: Nature Communications. - : NATURE RESEARCH. - 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- The ability to define an off state in logic electronics is the key ingredient that is impossible to fulfill using a conventional pristine graphene layer, due to the absence of an electronic bandgap. For years, this property has been the missing element for incorporating graphene into next-generation field effect transistors. In this work, we grow high-quality armchair graphene nanoribbons on the sidewalls of 6H-SiC mesa structures. Angle-resolved photoelectron spectroscopy (ARPES) and scanning tunneling spectroscopy measurements reveal the development of a width-dependent semiconducting gap driven by quantum confinement effects. Furthermore, ARPES demonstrates an ideal one-dimensional electronic behavior that is realized in a graphene-based environment, consisting of well-resolved subbands, dispersing and non-dispersing along and across the ribbons respectively. Our experimental findings, coupled with theoretical tight-binding calculations, set the grounds for a deeper exploration of quantum confinement phenomena and may open intriguing avenues for new low-power electronics. Here, the authors investigate armchair graphene nanoribbons by angle-resolved photoelectron spectroscopy, and show the development of a width-dependent semiconducting gap driven by quantum confinement effects, and an ideal one-dimensional electronic behaviour.
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| 4. |
- Nguyen, Thi Thuy Nhung, et al.
(författare)
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Topological Surface State in Epitaxial Zigzag Graphene Nanoribbons
- 2021
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 21:7, s. 2876-2882
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Tidskriftsartikel (refereegranskat)abstract
- Protected and spin-polarized transport channels are the hallmark of topological insulators, coming along with an intrinsic strong spin-orbit coupling. Here we identified such corresponding chiral states in epitaxially grown zigzag graphene nanoribbons (zz-GNRs), albeit with an extremely weak spin-orbit interaction. While the bulk of the monolayer zz-GNR is fully suspended across a SiC facet, the lower edge merges into the SiC(0001) substrate and reveals a surface state at the Fermi energy, which is extended along the edge and splits in energy toward the bulk. All of the spectroscopic details are precisely described within a tight binding model incorporating a Haldane term and strain effects. The concomitant breaking of time-reversal symmetry without the application of external magnetic fields is supported by ballistic transport revealing a conduction of G = e2/h.
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| 5. |
- Stöhr, Alexander, et al.
(författare)
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Graphene Ribbon Growth on Structured Silicon Carbide
- 2017
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Ingår i: Annalen der Physik. - : Wiley. - 0003-3804. ; 529:11
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Tidskriftsartikel (refereegranskat)abstract
- Structured Silicon Carbide was proposed to be an ideal template for the production of arrays of edge specific graphene nanoribbons (GNRs), which could be used as a base material for graphene transistors. We prepared periodic arrays of nanoscaled stripe-mesas on SiC surfaces using electron beam lithography and reactive ion etching. Subsequent epitaxial graphene growth by annealing is differentiated between the basal-plane mesas and the faceting stripe walls as monitored by means of atomic force microscopy (AFM). Microscopic low energy electron diffraction (μ-LEED) revealed that the graphene ribbons on the facetted mesa side walls grow in epitaxial relation to the basal-plane graphene with an armchair orientation at the facet edges. The π-band system of the ribbons exhibits linear bands with a Dirac like shape corresponding to monolayer graphene as identified by angle-resolved photoemission spectroscopy (ARPES).
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| 6. |
- Zakharov, Alexei, et al.
(författare)
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Wafer Scale Growth and Characterization of Edge Specific Graphene Nanoribbons for Nanoelectronics
- 2019
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Ingår i: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 2:1, s. 156-162
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Tidskriftsartikel (refereegranskat)abstract
- One of the ways to use graphene in field effect transistors is to introduce a band gap by quantum confinement effect. That is why narrow graphene nanoribbons (GNRs) with width less than 50 nm are considered to be essential components in future graphene electronics. The growth of graphene on sidewalls of SiC(0001) mesa structures using scalable photolithography was shown to produce high quality GNRs with excellent transport properties. Such epitaxial graphene nanoribbons are very important in fundamental science but if GNRs are supposed to be used in advanced nanoelectronics, high quality thin (<50 nm) nanoribbons should be produced on a large (wafer) scale. Here we present a technique for scalable template growth of high quality GNRs on Si-face of SiC(0001) and provide detailed structural information along with transport properties. For the first time we succeeded now to avoid SiC-facet instabilities in order to grow high quality GNRs along both [11̅00] and [112̅0] crystallographic directions on the same substrate. The quality of the grown nanoribbons was confirmed by comprehensive characterization with atomic resolution STM, dark field LEEM, and transport measurements. This approach generates an entirely new platform for both fundamental and application driven research of quasi one-dimensional carbon based magnetism and spintronics.
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