The effect of vacuum annealing on graphene

Ni, Zhenhua; Wang, Haomin; Luo, Zhi; Wang, Xiaocong; Yu, Ting; Wu, Yi; Shen, Zexiang

doi:10.1002/jrs.2485

Cited by 223 publications

(213 citation statements)

References 29 publications

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“…Annealing in forming gas and in vacuum results in the blue shift of the position of all three lines, D, G and 2D. There are two reasons for the blue shift of the Raman peaks after annealing: (i) hole doping caused by enhanced ability to adsorb oxygen and water molecules after vacuum annealing and sample exposure to ambient air 27,29,30 or (ii) compressive stress caused by the difference in the thermal expansion of graphene and substrate, slipping of the graphene film over substrate during heating and pinning of annealed at high T a film during cooling back to room temperature 16,[31][32][33][34][35] . It was shown in Ref.…”

Section: Resultsmentioning

confidence: 99%

Effect of annealing on Raman spectra of monolayer graphene samples gradually disordered by ion irradiation

Zion

Бутенко

Kaganovskii

et al. 2017

Journal of Applied Physics

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The Raman scattering spectra (RS) of two series of monolayer graphene samples irradiated with various doses of C + and Xe + ions were measured after annealing in high vacuum, and in forming gas (95%Ar+5%H2). It was found that these methods of annealing have dramatically different influence on the RS lines. Annealing in vacuum below 500 • C leads to significant decrease of both D-line, associated with defects, and 2D-line, associated with the intact lattice structure, which can be explained by annealing-induced enhanced doping. Further annealing in vacuum up to 1000 • C leads to significant increase of 2D-line together with continuous decrease of D-line, which gives evidence of partial removal of defects and recovery of the damaged lattice. Annealing in forming gas is less effective in this sense. The blue shift of all lines is observed after annealing. It is shown that below 500 • C, the unintentional doping is the main mechanism of shift, while at higher annealing temperatures, the lattice strain dominates due to mismatch of the thermal expansion coefficient of graphene and the SiO2 substrate. Inhomogeneous distribution of stress and doping across the samples leads to the correlated variation of the amplitude and the peak position of RS lines.

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Section: Resultsmentioning

confidence: 99%

Effect of annealing on Raman spectra of monolayer graphene samples gradually disordered by ion irradiation

Zion

Бутенко

Kaganovskii

et al. 2017

Journal of Applied Physics

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“…However, there is disagreement in the literature about the effects of annealing on the subject of strain and charge doping. Some research concluded that annealing alters the doping, by dopant transfer from the environment or the substrate, or out-gassing of dopants in doped graphene samples [28,45]. Other papers reported that compressive strain is induced in samples after annealing and that this is a competing explanation for the observed changes [19,27].…”

Section: Discussionmentioning

confidence: 99%

Effects of Thermal Annealing on the Properties of Mechanically Exfoliated Suspended and On-Substrate Few-Layer Graphene

2017

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Graphene's novel electrical, optical, and mechanical properties are affected both by substrate interaction and processing steps required to fabricate contacts and devices. Annealing is used to clean graphene devices, but this can lead to doping and defect changes and strain effects. There is often disagreement about which of these effects are occurring and which result in observed changes in Raman spectra. The effects of vacuum annealing on mechanically exfoliated pristine, suspended, and attached thin and thick few-layer graphene on SiO 2 /Si are investigated here using scanning electron microscopy (SEM), Raman spectroscopy, and atomic force microscopy (AFM). Before annealing, Raman shows that the differences in 2D and G band positions and the appearance of a disorder-induced D band of all regions were mainly because of compressive or tensile structural deformations emerging through mechanical exfoliation instead of charge doping. Annealing at low temperature is sufficient to eliminate most of the defects. However, compressive strain is induced in the sheet by annealing at high temperature, and for thin regions increased substrate conformation leads to the apparent disappearance of the sheets. The intensity ratio of the 2D and G bands also reduces with induced compressive strain, and thus should not be used to detect doping.

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“…These sources are often more problematic due to contamination occurring over large areas, rather than as individually adsorbed molecules. Unlike atmospheric contamination, the impurities deposited during experimental processes are often a) Electronic mail: g.h.wells@durham.ac.uk b) Electronic mail: m.r.c.hunt@durham.ac.uk metallic and bond more strongly to the surface preventing their removal via annealing 14,15 . With contamination of graphene samples occurring due to many different factors, which are often unavoidable, cleaning of graphene is important.…”

Section: Introductionmentioning

confidence: 99%

“…With contamination of graphene samples occurring due to many different factors, which are often unavoidable, cleaning of graphene is important. As a result, many different cleaning methods have been reported including mechanical sweeping with an atomic force microscope (AFM) tip 16,17 , the use of sacrificial metal layers 18 , the application of high currents 19 and high temperature annealing under vacuum 14,15 . Although these methods are appropriate for the removal of small concentrations of impurities they are less suitable for cleaning thicker contaminant layers over larger scales.…”

Section: Introductionmentioning

confidence: 99%

Facile technique for the removal of metal contamination from graphene

Wells

Hunt

Hopf

et al. 2015

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Metal contamination deposited on few-layer graphene (3±1 ML) grown on SiC(0001) was successfully removed from the surface, using low cost adhesive tape. More than 99% of deposited silver contamination was removed from the surface via peeling, causing minimal damage to the graphene. A small change in the adhesion of graphene to the SiC(0001) substrate was indicated by changes observed in pleat defects on the surface, however, atomic resolution images show the graphene lattice remains pristine. Thin layers of contamination deposited via an electron gun during AES/LEED measurements were also found to be removable by this technique. This contamination showed similarities to "roughened" graphene previously reported in the literature.

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The effect of vacuum annealing on graphene

Cited by 223 publications

References 29 publications

Effect of annealing on Raman spectra of monolayer graphene samples gradually disordered by ion irradiation

Effect of annealing on Raman spectra of monolayer graphene samples gradually disordered by ion irradiation

Effects of Thermal Annealing on the Properties of Mechanically Exfoliated Suspended and On-Substrate Few-Layer Graphene

Facile technique for the removal of metal contamination from graphene

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