Large-Area Synthesis of High-Quality and Uniform Graphene Films on Copper Foils
Summary (1 min read)
Summary
- Graphene has been attracting great interest because of its distinctive band structure and physical properties.
- The authors grew large area graphene films of the order of centimeters on copper substrates by chemical vapor deposition using methane.
- The films are predominantly single layer graphene with a small percentage, <5%, of the area having few layers, and are continuous across copper surface steps and grain boundaries.
- The low solubility of carbon in copper appears to help make this growth process self-limiting.
- Graphene film transfer processes to arbitrary substrates were also developed, and top gated field effect transistors fabricated on Si/SiO2 substrates showed electron mobilities as high as 4300 cm V s at room temperature.
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Cites background or methods from "Large-Area Synthesis of High-Qualit..."
..., 2009) and copper (Li et al., 2009), as well as directly unzipping carbon nanotubes (Kosynkin et al....
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...…have recently emerged several novel methods of fabricating graphene including chemical vapor deposition on nickel (Kim et al., 2009) and copper (Li et al., 2009), as well as directly unzipping carbon nanotubes (Kosynkin et al., 2009; Sinitskii et al., 2009) and other chemical methods (Jiao et…...
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Frequently Asked Questions (13)
Q2. How did the researchers measure the electrical quality of graphene?
In order to evaluate the electrical quality of the synthesized graphene, dual-gated field effect devices (FETs) using Al2O3 as the gate dielectric were fabricated and measured at room temperature.
Q3. What is the carrier mobility of graphene?
3. The extracted carrier mobility is ~4300 cm2V–1s–1, with the residual carrier concentration at the Dirac point of n0 = 3.2 × 1011 cm–2.
Q4. What is the effect of surface segregation on graphene?
Monolayer graphene formation caused by surface segregation or surface adsorption of carbon has also been observed on transition metals such as Ni and Co at elevated temperatures by Blakely and coauthors (20–22).
Q5. What is the important information about graphene?
An analysis of the intensity of the optical image over the whole sample (1 cm by 1 cm) showed that the area with the lightest pink color is more than 95%, and all 40 Raman spectra randomly collected from such area shows monolayer graphene.
Q6. Who is the author of this article?
The authors would like to thank the Nanoelectronic ResearchInitiative (NRI-SWAN; #2006-NE-1464), the DARPA CERA Center, and The University of Texas at Austin for support.
Q7. What is the description of graphene?
In recent work, thin Ni films and a “fast cooling” process were used to suppress the amount of precipitated C. However, this process still yields films with a wide range of graphene layer thicknesses, from 1 to a few tens of layers, and with defects associated with fast cooling (5–7).
Q8. What is the mechanism of graphene growth?
The precise mechanism will require additional experiments to understand, but very low C solubility in Cu (23–25), and poor C saturation as a result of graphene surface coverage may be playing a role in limiting or preventing the precipitation process altogether at high temperature, similar to the case of impeding of carburization of Ni (26).
Q9. What is the way to grow graphene on Cu?
Cu foils nor continuous multilayer graphene for thicker Cu foils, as the authors would have expected based on the precipitation mechanism.
Q10. What is the Raman spectra of the graphene on SiO2/Si?
The Raman spectra are from the spots marked with the corresponding colored circles shown in the other panels (in Fig. 2, A and B, green arrows are used instead of circles so as to show the trilayer region more clearly).
Q11. What is the corresponding map of the D band?
The D map, which has been associated with defects in graphene, in Fig. 2D is rather uniform and near the background level, except for regions where wrinkles are present and close to few-layer regions.
Q12. What is the important point of the paper?
According to these observations, the authors concluded that graphene is growing by a surface-catalyzed process rather than a precipitation process as reported by others for Ni (5–7).
Q13. What is the Raman spectrum of graphene?
The Raman spectrum from the lightest pink background in Fig. 2B shows typical features of monolayer graphene; e.g., ~0.5 G-to-2D intensity ratio, and a symmetric 2D band centered at ~2680 cm–1 with a full width at half maximum (FWHM) of ~33 cm–1.