Finding the hidden valence band of N  =  7 armchair graphene nanoribbons with angle-resolved photoemission spectroscopy

Senkovskiy, Boris V.; Usachov, Dmitry Yu.; Fedorov, Alexander; Haberer, Danny; Ehlen, Niels; Fischer, Felix R.; Grüneis, A.

doi:10.1088/2053-1583/aabb70

Cited by 24 publications

(76 citation statements)

References 56 publications

(113 reference statements)

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“…As we shall show later, DFT finds that this band corresponds instead to the VB-1 of the pristine rib-bon, which is however not visible in STS due to its nodal-plane structure. 9,34,35 Impurity states of 2B-AGNR. The dI/dV spectra in Fig.…”

Section: Resultsmentioning

confidence: 99%

Electronic Properties of Substitutionally Boron-Doped Graphene Nanoribbons on a Au(111) Surface

et al. 2018

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High quality graphene nanoribbons (GNRs) grown by on-surface synthesis strategies with atomic precision can be controllably doped by inserting heteroatoms or chemical groups in the molecular precursors. Here, we study the electronic structure of armchair GNRs substitutionally doped with diboron moieties at the center, through a combination of scanning tunneling spectroscopy, angle-resolved photoemission, and density functional theory simulations. Boron atoms appear with a small displacement towards the surface signal-ing their stronger interaction with the metal. We find two boron-rich flat bands emerging as impurity states inside the GNR band gap, one of them particularly broadened after its hybridization with the gold surface states. In addition, the boron atoms shift the conduction and valence bands of the pristine GNR away from the gap edge, and leave unaffected the bands above and below, which become the new frontier bands and have negligible boron character. This is due to the selective mixing of boron states with GNR bands according to their symmetry. Our results depict that the GNRs band structure can be tuned by modifying the separation between di-boron moieties.

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Section: Resultsmentioning

confidence: 99%

Electronic Properties of Substitutionally Boron-Doped Graphene Nanoribbons on a Au(111) Surface

et al. 2018

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“…(c) Second derivative with respect to momentum of the ARPES scan (to enhance the contrast) of fused GNRs on Au(788) measured along the GNR axis (k ) with fixed in-plane momentum perpendicular to the axis (k ⊥ ). 20 To maximize the photoemission intensity from VB 1 14-AGNR , we used k ⊥ = 1.1 Å −1 . At this k ⊥ the intensities from VB 2 14-AGNR and VB 2 7-AGNR overlap (Supplementary Section 2).…”

Section: Synthesis and Characterization Of Gnr Heterojunctionsmentioning

confidence: 99%

“…is the barrier height as a function of the coordinate x, Φ b denotes the barrier height at x = 0, and m is the effective mass inside the barrier which we take from ARPES data. 20 The prefactor A is proportional to the number of parallel 1D channels across the source-drain contacts and it was not allowed to vary significantly for all devices and it was kept constant for the L-dependent measurements shown below.…”

Section: Tunneling Barrier Analysis Of Transport Measurementsmentioning

confidence: 99%

“…S7), in agreement with previous work in the high-doping regime where the mismatch in density of states within bulk and contact graphene regions imparts asymmetry to the field effect. 35 identical to the synthesis of densely aligned 7-AGNRs on Au(788) 18,20,22 while the third step is performed at higher temperature and longer annealing time. The annealing temperature and time were optimized to get a maximum amount of 14-AGNRs using in situ studies with UHV Raman spectroscopy (Supplementary Section 4).…”

Section: Tunneling Current Modulation By Adsorbatesmentioning

confidence: 99%

“…S2 was calculated using the dipole approximation for the matrix element with a plane wave as a final state. 20,38 Raman spectroscopy measurements All Raman measurements presented in this work were performed in the back-scattering geometry using a Renishaw inVia setup with a 633 nm laser at room temperature. UHV Raman studies shown in Fig.…”

Section: Tunneling Current Modulation By Adsorbatesmentioning

confidence: 99%

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Tunneling current modulation in atomically precise graphene nanoribbon heterojunctions

Senkovskiy

Nenashev

Alavi

et al. 2020

Preprint

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Lateral heterojunctions of atomically precise graphene nanoribbons (GNRs) hold promise for applications in nanotechnology, yet their charge transport and most of the spectroscopic properties have not been investigated. Here, we synthesize a monolayer of multiple aligned heterojunctions consisting of quasi-metallic and wide-bandgap GNRs, and report characterization by scanning tunneling microscopy, angle-resolved photoemission, Raman spectroscopy, and charge transport. Comprehensive transport measurements as a function of bias and gate voltages, channel length, and temperature reveal that charge transport is dictated by tunneling through the potential barriers formed by wide-bandgap GNR segments. The current-voltage characteristics are in agreement with calculations of tunneling conductance through asymmetric barriers. We fabricate a GNR heterojunctions based sensor and demonstrate greatly improved sensitivity to adsorbates compared to graphene based sensors. This is achieved via a new concept in sensing, namely the modulation of the tunneling barriers by adsorbates.

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Robust Contact by Direct Formation of CAu Bond in Suspended Armchair Graphene Nanoribbon

Hassanien

2024

Physica Rapid Research Ltrs

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The Schottky contact between metal electrode and armchair graphene nanoribbon (AGNR) plays a fundamental role in limiting the current flow as well as the overall device characteristics. To improve device performance, the metal electrode must be engineered to lower barrier height and allow low‐resistance ohmic contact. Nevertheless, in most cases, this gives rise to interfacial states which dictate the contact properties and induce Fermi level pinning. Herein, another strategy to form robust and transparent 7‐atom‐wide‐AGNR (7‐AGNR)/Au contacts in which a direct CAu σ bond is initialized by the tip of scanning tunneling microscope (STM) on a dehydrogenated terminus is demonstrated. This process has led to a total lift‐off of 7‐AGNR from the Au(111) substrate and allowed us to visualize the details of the band structure. Furthermore, it is found that GNR is useful as an STM tip for high‐resolution selective imaging of edge states showing a unique interference pattern with a periodicity that coincides with half of Fermi wavelength of GNR lattice. The combination of imaging and tunneling spectroscopy with GNR‐tip is promising for unraveling intrinsic details in the band structure which are of fundamental importance to understand the transport properties of GNRs devices.

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Finding the hidden valence band of N = 7 armchair graphene nanoribbons with angle-resolved photoemission spectroscopy

Cited by 24 publications

References 56 publications

Electronic Properties of Substitutionally Boron-Doped Graphene Nanoribbons on a Au(111) Surface

Electronic Properties of Substitutionally Boron-Doped Graphene Nanoribbons on a Au(111) Surface

Tunneling current modulation in atomically precise graphene nanoribbon heterojunctions

Robust Contact by Direct Formation of CAu Bond in Suspended Armchair Graphene Nanoribbon

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