Ultraclean freestanding graphene by platinum-metal catalysis

Longchamp, Jean-Nicolas; Escher, Conrad; Fink, Hans‐Werner

doi:10.1116/1.4793746

Cited by 49 publications

(57 citation statements)

References 27 publications

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“…Hence, transmission signal is captured within a full angle of 77°. Freestanding graphene over holes of 2 micrometer in diameter in a palladium coated silicon nitride membrane is prepared following the procedure described elsewhere [23].…”

Section: Experimental Methods and Resultsmentioning

confidence: 99%

Mapping unoccupied electronic states of freestanding graphene by angle-resolved low-energy electron transmission

et al. 2016

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We report angle-resolved electron transmission measurements through freestanding graphene sheets in the energy range of 18 to 30 eV above the Fermi level. The measurements are carried out in a low-energy electron point source microscope, which allows simultaneously probing the transmission for a large angular range. The characteristics of low-energy electron transmission through graphene depend on its electronic structure above the vacuum level. The experimental technique described here allows mapping of the unoccupied band structure of freestanding two-dimensional materials as a function of the energy and probing angle, respectively, in-plane momentum. Our experimental findings are consistent with theoretical predictions of a resonance in the band structure of graphene above the vacuum level [V. U. Nazarov, E. E. Krasovskii, and V. M. Silkin, Phys. Rev. B 87, 041405 (2013)].

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Section: Experimental Methods and Resultsmentioning

confidence: 99%

Mapping unoccupied electronic states of freestanding graphene by angle-resolved low-energy electron transmission

et al. 2016

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“…The electrical properties of the resulting graphene sheets, which have micro-scale polymer deposits, are degraded through contact resistance and charge transfer between the contaminants and the graphene. Similar concerns exist for other graphene production methods such as liquid phase exfoliation 11-12 . Various methods have been presented in the literature for removing organic contamination layers from graphene, including ultra-violet (UV) ozone treatment, argon plasma etching, vacuum annealing, annealing on a catalyst, contact-mode atomic force microscopy (AFM), and CO 2 cluster jet conditioning 9,[13][14][15][16][17][18] . None of these methods are optimal for large scale micro-electronics manufacturing.…”

Section: Introductionmentioning

confidence: 99%

Removal of Organic Contamination from Graphene with a Controllable Mass-Selected Argon Gas Cluster Ion Beam

et al. 2015

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Since the discovery of graphene, organic surface contamination has posed difficulties both for accurate characterization of the material's intrinsic properties and for development of graphene devices. In this study, we investigate the use of a mass-selected argon gas cluster ion beam for removing organic contaminants, such as residual polymethylmethacrylate (PMMA), from single-layer graphene. The influence of cluster ion size, energy and ion dose has been investigated to identify the important factors for minimizing damage to the graphene layer during the cleaning process. Raman spectroscopy was used to analyse the variation in the D-peak and G-peak intensity ratio, an indicator of damage to the graphene lattice, as a function of ion beam dose and kinetic energy per atom (E/n) in the cluster ions.Using a mass-selected 5.0 keV Ar 5000 beam with a dose of 5.00 ions/nm 2 , we were able to demonstrate removal of polymer residue and other carbonaceous material from single-layer CVD-grown graphene whilst minimizing the damage to the graphene itself. This demonstrates that the mass-selected argon cluster ion beam is a suitable, industry-relevant technology for use in large scale production of commercially-desirable CVD-grown graphene.

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“…We also perform a comparative cleanliness analysis of our approach with two widely used transfer methods: (i) direct transfer by IPA 12 and (ii) PMMA-based transfer. 9 The samples transferred via all three aforementioned protocols were subjected to the same two step cleaning procedure after the transfer: annealing in the presence of platinum catalyst 25 followed by annealing in activated carbon. 26 The cleanliness of the resultant membranes was examined with techniques highly sensitive to the surface contamination and defects: low-voltage (1 keV) scanning electron microscopy (LVSEM), x-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM).…”

Section: Introductionmentioning

confidence: 99%

Toward clean suspended CVD graphene

et al. 2016

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The application of suspended graphene as electron transparent supporting media in electron microscopy, vacuum electronics, and micromechanical devices requires the least destructive and maximally clean transfer from their original growth substrate to the target of interest. Here, we use thermally evaporated anthracene films as the sacrificial layer for graphene transfer onto an arbitrary substrate. We show that clean suspended graphene can be achieved via desorbing the anthracene layer at temperatures in the 100 °C to 150 °C range, followed by two sequential annealing steps for the final cleaning, using Pt catalyst and activated carbon. The cleanliness of the suspended graphene membranes was analyzed employing the high surface sensitivity of low energy scanning electron microscopy and x-ray photoelectron spectroscopy. A quantitative comparison with two other commonly used transfer methods revealed the superiority of the anthracene approach to obtain larger area of clean, suspended CVD graphene. Our graphene transfer method based on anthracene paves the way for integrating cleaner graphene in various types of complex devices, including the ones that are heat and humidity sensitive.

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Ultraclean freestanding graphene by platinum-metal catalysis

Cited by 49 publications

References 27 publications

Mapping unoccupied electronic states of freestanding graphene by angle-resolved low-energy electron transmission

Mapping unoccupied electronic states of freestanding graphene by angle-resolved low-energy electron transmission

Removal of Organic Contamination from Graphene with a Controllable Mass-Selected Argon Gas Cluster Ion Beam

Toward clean suspended CVD graphene

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