Graphene Strained by Defects

Robinson, Jeremy T.; Zalalutdinov, Maxim; Cress, Cory D.; Culbertson, James C.; Friedman, Adam L.; Merrill, Andrew; Landi, Brian J.

doi:10.1021/acsnano.7b00923

Cited by 26 publications

(25 citation statements)

References 32 publications

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“…Here we show methods to fabricate nanostructures and access buried interfaces with the precision of a single atomic layer by using graphene as impermeable etch masks and etch stops 16 , 17 . These techniques, which we call GES (graphene etch stops), represent a straightforward method to selectively expose and contact embedded graphene layers within 2D heterostructures.…”

Section: Introductionmentioning

confidence: 99%

“…In contrast, graphene reacts with XeF 2 to form fluorographene (FG) 21 – 24 , a wide band-gap semiconducting monolayer 21 , 22 with composition C 4 F, in the case that only one side is exposed 22 . There have been several demonstrations that take advantage of this selectivity to use graphene as an etch mask for shaping MoS 2 16 , as a mask to etch underlying silicon 25 – 27 , and to create a sacrificial release layer to suspend graphene membranes on silicon on insulator 17 , 22 . Our innovation has been to apply this etch selectivity to access buried graphene layers embedded within the heterostructures and as masks for patterning the underlying layers.…”

Section: Introductionmentioning

confidence: 99%

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Atomically precise graphene etch stops for three dimensional integrated systems from two dimensional material heterostructures

et al. 2018

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Atomically precise fabrication methods are critical for the development of next-generation technologies. For example, in nanoelectronics based on van der Waals heterostructures, where two-dimensional materials are stacked to form devices with nanometer thicknesses, a major challenge is patterning with atomic precision and individually addressing each molecular layer. Here we demonstrate an atomically thin graphene etch stop for patterning van der Waals heterostructures through the selective etch of two-dimensional materials with xenon difluoride gas. Graphene etch stops enable one-step patterning of sophisticated devices from heterostructures by accessing buried layers and forming one-dimensional contacts. Graphene transistors with fluorinated graphene contacts show a room temperature mobility of 40,000 cm2 V−1 s−1 at carrier density of 4 × 1012 cm−2 and contact resistivity of 80 Ω·μm. We demonstrate the versatility of graphene etch stops with three-dimensionally integrated nanoelectronics with multiple active layers and nanoelectromechanical devices with performance comparable to the state-of-the-art.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Atomically precise graphene etch stops for three dimensional integrated systems from two dimensional material heterostructures

et al. 2018

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“…In the horizontal axis, 0 eV indicates the fermi level energy. (a) Graphenylene based nanotube with chiral indexes (8,2) with no strain (e = 0%). It is important to note that the green curve (2s orbitals contribution) is close to zero, and practically coincides with the horizontal axis in black and cannot be seen clearly.…”

Section: Discussionmentioning

confidence: 99%

“…Fig. 10(a) shows our results for PG based nanotubes where one can see that, starting with e ¼ 0, higher strain values correspond to smaller gap values with a monotonic decrease for (6, 0) and (8,2) tubes. On the other hand, the (4, 4) tube presents a minimum at e $ 0:1 and the gap opening increases again for higher deformations, although the values still smaller than 3.2 eV up to the maximum strain considered.…”

Section: Electronic Structurementioning

confidence: 91%

“…1) which presents unusual and interesting electronic and mechanical properties [2]. Because of these properties it may be used in diverse applications, for example electronics [3,4], water separation [5], nanomechanical resonators [6][7][8], chemical sensors [9], or in producing exotic materials [10][11][12][13][14]. However, in its pristine form, graphene is a gapless semiconductor.…”

Section: Introductionmentioning

confidence: 99%

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Porous graphene and graphenylene nanotubes: Electronic structure and strain effects

Fabris

Junkermeier

Paupitz

2017

Computational Materials Science

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a b s t r a c tThe unusual and unique mechanical and electronic properties of nanostructured carbon materials make them useful in the construction of nanodevices. We investigate a new class of structures, called porous nanotubes, which are constructed from two recently synthesized two-dimensional materials, namely the porous graphene (PG) and the two-dimensional carbon allotrope known as graphenylene, also known as Biphenylene Carbon (BPC). We investigate this class of quasi-one-dimensional materials using the density functional tight-binding (DFTB) method to optimize geometries and to calculate electronic structure features of these systems. For each type of porous nanotube, calculations were performed on tubes with several diameters and chiralities. Our results show that the PG nanotubes have a wide band-gap, $ 3:3 eV, and the graphenylene nanotubes have a semiconductor behavior with a band gap around 0.7 eV. They also show that as the diameter of a PG nanotube increases the band-gap decreases, while for the graphenylene nanotube the band gap increases. In both cases, the observed gap variation with increasing diameter is towards the value found for the respective two-dimensional membrane. Calculations on axially strained porous nanotubes show a decrease on the band gap of $ 10% for some chiralities of the PG nanotube and an increase for the graphenylene nanotubes gap that can become as high as 100%. These results are in contrast with the expected behavior for carbon nanotubes, which show a linear dependence between gap opening and applied strain under similar conditions.

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Engineering Carbon Materials for Electrochemical Oxygen Reduction Reactions

Lin

Miao

Wallace

et al. 2021

Advanced Energy Materials

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exchange membrane fuel cells (PEMFCs) and metal-air batteries, the ORR starts from the adsorption of O 2 molecules at the cathode, electrochemical activation of the OO bond, and then the formation of O-containing groups such as OOH*, O*, and OH*. In this way, O 2 is reduced by the electrons (Figure 1a). [4] The efficiency of these energy devices is usually determined by that of the ORR process. However, the strong bond energy of OO (498 kJ mol −1 ) means that the ORR at the electrode is not easy, especially compared to the hydrogen oxidation reaction (HOR: H 2 →2H + + 2e − ) at the anode of hydrogen-oxygen fuel cells (Figure 1a). Improvement of OO bond activation and cleavage with catalysts is therefore highly important in developing efficient energy storage and conversion systems as well as fast and efficient chemical production techniques.Nevertheless, in industry, the most common ORR catalysts are still Pt-based materials, which are prohibitively expensive for wider application (Figure 1b). [5] There is a pressing need to explore alternative electrocatalysts that are cheap and stable. Significant efforts have been made to develop alternative materials (e.g., transition metal oxides, alloys, metal-organic frameworks/MOFs, single atom catalyst) and investigate their catalytic mechanisms, [6][7][8][9][10][11][12] but challenges remain. In 2009, Dai's group reported using doped carbon nanotubes (CNTs) to catalyze ORR that exhibited better catalytic efficiency than commercial Pt/C electrodes in alkaline media. [13] It should be noted that, in alkaline media, the hydroxide conducting polymeric membranes (e.g., in anion exchange membrane fuel cells) are unstable and have poor resistance to CO 2 , while the overpotentials for hydrogen oxidation are also high. [14][15][16] Compared to metal-based catalysts, carbon materials have significant merits of outstanding anti-corrosion performance and electrochemical durability, as well as the possibility of low-cost manufacture. This combination means that carbon materials are seen as highly promising candidates to replace precious metals as ORR. In the years following Dai's pioneering work, various other doped carbon materials were further developed and their catalytic mechanisms investigated. [17][18][19][20][21][22] Some more recent studies explored this further and suggested that active intrinsic carbon structural defects are associated with efficient ORR catalysis (Figure 2b). [23][24][25][26] Although great progress has been achieved on this topic, the origin and mechanism of the ORR activity are still not fully clear. Beyond the catalytic activity, no pattern has been established in the selectivityThe electrochemical oxygen reduction reaction (ORR) is the key energy conversion reaction involved in fuel cells, metal-air batteries, and hydrogen peroxide production. Proliferation and improvement of the ORR requires wider use of new and existing high performance catalysts; unfortunately, most of these are still based on precious metals and become uneconomical in massuse ...

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Graphene Strained by Defects

Cited by 26 publications

References 32 publications

Atomically precise graphene etch stops for three dimensional integrated systems from two dimensional material heterostructures

Atomically precise graphene etch stops for three dimensional integrated systems from two dimensional material heterostructures

Porous graphene and graphenylene nanotubes: Electronic structure and strain effects

Engineering Carbon Materials for Electrochemical Oxygen Reduction Reactions

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