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Probing substrate influence on graphene by analyzing Raman lineshapes.

Huang CH, Lin HY, Huang CW, Liu YM, Shih FY, Wang WH, Chui HC - Nanoscale Res Lett (2014)

Bottom Line: Distinguishing the substrate influences or the doping effects of charged impurities on graphene can be realized by optically probing the graphene surfaces, included the suspended and supported graphene.For the Gaussian part, the suspended graphene exhibits much greater Gaussian bandwidths than those of the supported graphene.It reveals that the doping effect on supported graphene is stronger than that of suspended graphene.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Photonics, National Cheng Kung University, Tainan 70101, Taiwan. hcchui@mail.ncku.edu.tw.

ABSTRACT
We provide a new approach to identify the substrate influence on graphene surface. Distinguishing the substrate influences or the doping effects of charged impurities on graphene can be realized by optically probing the graphene surfaces, included the suspended and supported graphene. In this work, the line scan of Raman spectroscopy was performed across the graphene surface on the ordered square hole. Then, the bandwidths of G-band and 2D-band were fitted into the Voigt profile, a convolution of Gaussian and Lorentzian profiles. The bandwidths of Lorentzian parts were kept as constant whether it is the suspended and supported graphene. For the Gaussian part, the suspended graphene exhibits much greater Gaussian bandwidths than those of the supported graphene. It reveals that the doping effect on supported graphene is stronger than that of suspended graphene. Compared with the previous studies, we also used the peak positions of G bands, and I2D/IG ratios to confirm that our method really works. For the suspended graphene, the peak positions of G band are downshifted with respect to supported graphene, and the I2D/IG ratios of suspended graphene are larger than those of supported graphene. With data fitting into Voigt profile, one can find out the information behind the lineshapes.

No MeSH data available.


Bandwidths of G band of the probed area by scanning the mapping points on suspended graphene. By fitting with Voigt function contained (green triangle) Lorentzian part and (red circle) Gaussian part.
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Figure 5: Bandwidths of G band of the probed area by scanning the mapping points on suspended graphene. By fitting with Voigt function contained (green triangle) Lorentzian part and (red circle) Gaussian part.

Mentions: The Lorentzian bandwidths on the suspended and supported graphene are kept as 12.09 ± 0.76 cm-1. The Lorentzian bandwidth is mainly contributed by the natural linewidth and partly from the uncertainty of data fitting (0.3 cm-1) and instrumental uncertainty (0.9 cm-1). The natural linewidth is just linked with the phonon lifetimes between interaction levels. On the other hand, the Gaussian bandwidths of the suspended graphene exhibit a much higher than those of the supported graphene. Some mechanisms resulted in the Gaussian bandwidth broadening and the curve is consistent with the deformation of graphene surface. Other broadening mechanisms are related to the substrate effect and the local heating effect (Figure 5).


Probing substrate influence on graphene by analyzing Raman lineshapes.

Huang CH, Lin HY, Huang CW, Liu YM, Shih FY, Wang WH, Chui HC - Nanoscale Res Lett (2014)

Bandwidths of G band of the probed area by scanning the mapping points on suspended graphene. By fitting with Voigt function contained (green triangle) Lorentzian part and (red circle) Gaussian part.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3924919&req=5

Figure 5: Bandwidths of G band of the probed area by scanning the mapping points on suspended graphene. By fitting with Voigt function contained (green triangle) Lorentzian part and (red circle) Gaussian part.
Mentions: The Lorentzian bandwidths on the suspended and supported graphene are kept as 12.09 ± 0.76 cm-1. The Lorentzian bandwidth is mainly contributed by the natural linewidth and partly from the uncertainty of data fitting (0.3 cm-1) and instrumental uncertainty (0.9 cm-1). The natural linewidth is just linked with the phonon lifetimes between interaction levels. On the other hand, the Gaussian bandwidths of the suspended graphene exhibit a much higher than those of the supported graphene. Some mechanisms resulted in the Gaussian bandwidth broadening and the curve is consistent with the deformation of graphene surface. Other broadening mechanisms are related to the substrate effect and the local heating effect (Figure 5).

Bottom Line: Distinguishing the substrate influences or the doping effects of charged impurities on graphene can be realized by optically probing the graphene surfaces, included the suspended and supported graphene.For the Gaussian part, the suspended graphene exhibits much greater Gaussian bandwidths than those of the supported graphene.It reveals that the doping effect on supported graphene is stronger than that of suspended graphene.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Photonics, National Cheng Kung University, Tainan 70101, Taiwan. hcchui@mail.ncku.edu.tw.

ABSTRACT
We provide a new approach to identify the substrate influence on graphene surface. Distinguishing the substrate influences or the doping effects of charged impurities on graphene can be realized by optically probing the graphene surfaces, included the suspended and supported graphene. In this work, the line scan of Raman spectroscopy was performed across the graphene surface on the ordered square hole. Then, the bandwidths of G-band and 2D-band were fitted into the Voigt profile, a convolution of Gaussian and Lorentzian profiles. The bandwidths of Lorentzian parts were kept as constant whether it is the suspended and supported graphene. For the Gaussian part, the suspended graphene exhibits much greater Gaussian bandwidths than those of the supported graphene. It reveals that the doping effect on supported graphene is stronger than that of suspended graphene. Compared with the previous studies, we also used the peak positions of G bands, and I2D/IG ratios to confirm that our method really works. For the suspended graphene, the peak positions of G band are downshifted with respect to supported graphene, and the I2D/IG ratios of suspended graphene are larger than those of supported graphene. With data fitting into Voigt profile, one can find out the information behind the lineshapes.

No MeSH data available.