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The deviation of growth model for transparent conductive graphene.

Chan SH, Chen JW, Chen HP, Wei HS, Li MC, Chen SH, Lee CC, Kuo CC - Nanoscale Res Lett (2014)

Bottom Line: The Raman intensity ratio of the G-peak to the 2D peak of the graphene film was as high as ~4 when the hydrogen flow rate was 30 sccm.The fitting curve obtained by the deviation equation of growth model closely matches the data.We believe that under the same conditions and with the same setup, the presented growth model can help manufacturers and academics to predict graphene growth time more accurately.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Optics and Photonics/Thin Film Technology Center, National Central University, 300 Chung-Da Rd, Chung-Li 32001, Taiwan.

ABSTRACT
An approximate growth model was employed to predict the time required to grow a graphene film by chemical vapor deposition (CVD). Monolayer graphene films were synthesized on Cu foil at various hydrogen flow rates from 10 to 50 sccm. The sheet resistance of the graphene film was 310Ω/□ and the optical transmittance was 97.7%. The Raman intensity ratio of the G-peak to the 2D peak of the graphene film was as high as ~4 when the hydrogen flow rate was 30 sccm. The fitting curve obtained by the deviation equation of growth model closely matches the data. We believe that under the same conditions and with the same setup, the presented growth model can help manufacturers and academics to predict graphene growth time more accurately.

No MeSH data available.


Optical transmittance and sheet resistance of graphene film. (a) Optical transmittance of graphene film. (b) Sheet resistance of graphene film obtained using various hydrogen flow rates from 10 to 50 sccm.
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Figure 5: Optical transmittance and sheet resistance of graphene film. (a) Optical transmittance of graphene film. (b) Sheet resistance of graphene film obtained using various hydrogen flow rates from 10 to 50 sccm.

Mentions: The A is a quadratic equation which means the graphene domains grown with an acceleration rate on the Cu foil. Equation 7 can be utilized to predict the coverage area of graphene on the Cu foil under various hydrogen flow rates from 10 to 50 sccm, as displayed in Figure 4. The dashed line is the area of the Cu foil (1.1 cm2) and the red spots represent the growth times of graphene that yield the specified area, based on Equation 7. A red spot at the dashed line indicates that the graphene fully covered the Cu foil. Figure 4 reveals that the graphene fully covered the foil when the hydrogen flow rate was 10, 20, or 30. When the hydrogen flow rate exceeded 30 sccm, the graphene did not fully cover the Cu foil because of the etching effect and thermal equilibrium occurs on the edge of graphene domains. Also, a fitting equation is obtained for the growth of graphene with different hydrogen flow rate, which is plotted as the blue curve. Based on the developed growth model, we can adjust any coverage of graphene on the Cu foil which closely matches the fitting curve; the growth model predicts the growth rate of graphene. As mentioned above, the graphene domain was hexagonal when the hydrogen flow rate was 30 sccm. The graphene fully covered the Cu foil both according to the growth model and in the experiment. The graphene was transferred onto a glass substrate to measure its transparency, sheet resistance, and Raman shift. In Figure 5a, the graphene film is placed on the glass substrate with a relatively high transmittance of about 97.7% at λ =550 nm. The attenuation coefficient (α =2.3%) was fitted using Beer’s law; the value matches the theoretical value of 2.3% when the λ =550 nm[15]. The graphene films that were synthesized using various hydrogen flow rates were also transferred to the substrate and their sheet resistance was measured, as shown in Figure 5b. The lowest obtained sheet resistance of graphene was 310Ω/□, which was achieved when the hydrogen flow rate was 30 sccm, because the smooth edge of the graphene domain reduced the number of scattering centers which inhibited the carrier transportation. The sheet resistance increased with the hydrogen flow rate over 30 sccm because the graphene did not fully cover the Cu foil, and because the larger number of pores in the graphene increased the sheet resistance. Figure 6 shows the Raman spectrum of graphene film, in which the peaks are typical of a single-layer graphene, with a 2D/G ratio of as high as ~4 when the hydrogen flow rate was 30 sccm. The full width at half maximum (FWHM) was 23.5 cm-1, verifying the presence of a single-layer graphene[8].


The deviation of growth model for transparent conductive graphene.

Chan SH, Chen JW, Chen HP, Wei HS, Li MC, Chen SH, Lee CC, Kuo CC - Nanoscale Res Lett (2014)

Optical transmittance and sheet resistance of graphene film. (a) Optical transmittance of graphene film. (b) Sheet resistance of graphene film obtained using various hydrogen flow rates from 10 to 50 sccm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4214604&req=5

Figure 5: Optical transmittance and sheet resistance of graphene film. (a) Optical transmittance of graphene film. (b) Sheet resistance of graphene film obtained using various hydrogen flow rates from 10 to 50 sccm.
Mentions: The A is a quadratic equation which means the graphene domains grown with an acceleration rate on the Cu foil. Equation 7 can be utilized to predict the coverage area of graphene on the Cu foil under various hydrogen flow rates from 10 to 50 sccm, as displayed in Figure 4. The dashed line is the area of the Cu foil (1.1 cm2) and the red spots represent the growth times of graphene that yield the specified area, based on Equation 7. A red spot at the dashed line indicates that the graphene fully covered the Cu foil. Figure 4 reveals that the graphene fully covered the foil when the hydrogen flow rate was 10, 20, or 30. When the hydrogen flow rate exceeded 30 sccm, the graphene did not fully cover the Cu foil because of the etching effect and thermal equilibrium occurs on the edge of graphene domains. Also, a fitting equation is obtained for the growth of graphene with different hydrogen flow rate, which is plotted as the blue curve. Based on the developed growth model, we can adjust any coverage of graphene on the Cu foil which closely matches the fitting curve; the growth model predicts the growth rate of graphene. As mentioned above, the graphene domain was hexagonal when the hydrogen flow rate was 30 sccm. The graphene fully covered the Cu foil both according to the growth model and in the experiment. The graphene was transferred onto a glass substrate to measure its transparency, sheet resistance, and Raman shift. In Figure 5a, the graphene film is placed on the glass substrate with a relatively high transmittance of about 97.7% at λ =550 nm. The attenuation coefficient (α =2.3%) was fitted using Beer’s law; the value matches the theoretical value of 2.3% when the λ =550 nm[15]. The graphene films that were synthesized using various hydrogen flow rates were also transferred to the substrate and their sheet resistance was measured, as shown in Figure 5b. The lowest obtained sheet resistance of graphene was 310Ω/□, which was achieved when the hydrogen flow rate was 30 sccm, because the smooth edge of the graphene domain reduced the number of scattering centers which inhibited the carrier transportation. The sheet resistance increased with the hydrogen flow rate over 30 sccm because the graphene did not fully cover the Cu foil, and because the larger number of pores in the graphene increased the sheet resistance. Figure 6 shows the Raman spectrum of graphene film, in which the peaks are typical of a single-layer graphene, with a 2D/G ratio of as high as ~4 when the hydrogen flow rate was 30 sccm. The full width at half maximum (FWHM) was 23.5 cm-1, verifying the presence of a single-layer graphene[8].

Bottom Line: The Raman intensity ratio of the G-peak to the 2D peak of the graphene film was as high as ~4 when the hydrogen flow rate was 30 sccm.The fitting curve obtained by the deviation equation of growth model closely matches the data.We believe that under the same conditions and with the same setup, the presented growth model can help manufacturers and academics to predict graphene growth time more accurately.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Optics and Photonics/Thin Film Technology Center, National Central University, 300 Chung-Da Rd, Chung-Li 32001, Taiwan.

ABSTRACT
An approximate growth model was employed to predict the time required to grow a graphene film by chemical vapor deposition (CVD). Monolayer graphene films were synthesized on Cu foil at various hydrogen flow rates from 10 to 50 sccm. The sheet resistance of the graphene film was 310Ω/□ and the optical transmittance was 97.7%. The Raman intensity ratio of the G-peak to the 2D peak of the graphene film was as high as ~4 when the hydrogen flow rate was 30 sccm. The fitting curve obtained by the deviation equation of growth model closely matches the data. We believe that under the same conditions and with the same setup, the presented growth model can help manufacturers and academics to predict graphene growth time more accurately.

No MeSH data available.