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Polarized Raman spectroscopy with differing angles of laser incidence on single-layer graphene.

Heo G, Kim YS, Chun SH, Seong MJ - Nanoscale Res Lett (2015)

Bottom Line: In an out-of-plane configuration, the angle between the polarization vector and the graphene plane is the same as the angle of laser incidence (θ).The normalized Raman intensity of the G-band measured in the out-of-plane configuration, with respect to that in the in-plane configuration, was analyzed as a function of θ.The normalized Raman intensity showed approximately cos(2) θ-dependence up to θ = 70°, which can be explained by the fact that only the electric field component of the incident and the scattered photon in the out-of-plane configuration projected onto the graphene plane can contribute to the Raman scattering process because of the perfect confinement of the electrons to the graphene plane.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Chung-Ang University, Seoul, 156-756 Republic of Korea.

ABSTRACT
Chemical vapor deposition (CVD)-grown single-layer graphene samples, transferred onto a transmission electron microscope (TEM) grid and onto a quartz plate, were studied using polarized Raman spectroscopy with differing angles of laser incidence (θ). Two different polarization configurations are used. In an in-plane configuration, the polarization direction of both incident and scattered light is parallel to the graphene plane. In an out-of-plane configuration, the angle between the polarization vector and the graphene plane is the same as the angle of laser incidence (θ). The normalized Raman intensity of the G-band measured in the out-of-plane configuration, with respect to that in the in-plane configuration, was analyzed as a function of θ. The normalized Raman intensity showed approximately cos(2) θ-dependence up to θ = 70°, which can be explained by the fact that only the electric field component of the incident and the scattered photon in the out-of-plane configuration projected onto the graphene plane can contribute to the Raman scattering process because of the perfect confinement of the electrons to the graphene plane.

No MeSH data available.


Related in: MedlinePlus

Polarized Raman spectra of a monolayer graphene on a TEM grid in the backscattering geometry. (a) Polarized Raman spectra of a monolayer graphene on a TEM grid in the backscattering geometry with differing angles (θ) of the laser incidence. Excitation laser wavelength was 532 nm. The black curves are Raman spectra measured with in-plane configuration and the red ones measured with out-of-plane configuration. (b, c) Normalized Raman intensity of the G-band (b) and the 2D-band (c) in out-of-plane configuration with respect to that in in-plane configuration as a function of laser incidence angle, respectively. The black lines represent cos2θ.
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Fig3: Polarized Raman spectra of a monolayer graphene on a TEM grid in the backscattering geometry. (a) Polarized Raman spectra of a monolayer graphene on a TEM grid in the backscattering geometry with differing angles (θ) of the laser incidence. Excitation laser wavelength was 532 nm. The black curves are Raman spectra measured with in-plane configuration and the red ones measured with out-of-plane configuration. (b, c) Normalized Raman intensity of the G-band (b) and the 2D-band (c) in out-of-plane configuration with respect to that in in-plane configuration as a function of laser incidence angle, respectively. The black lines represent cos2θ.

Mentions: Figure 3a shows the Raman spectra for different angles of laser incidence onto the single-layer graphene on a TEM grid in the backscattering geometry, where the black lines and the red lines correspond to the Raman spectra taken in (VV) and (HH) polarization configurations, respectively. In the (HH) polarization configuration, the entire electric field vector of the incident light cannot interact with the electrons on the graphene whereas it can interact with them in the (VV) polarization configuration, as shown in Figure 1b. In fact, only the projected component of the electric field vector of the incident light onto the graphene plane can effectively contribute to Raman scattering process as illustrated in Figure 1b. This is exactly the same situation as the polarized Raman scattering on single isolated CNT, where the Raman intensities of the G-band and the RBM of the CNT exhibited approximately cos2α-dependence in which α is the angle between the CNT axis and the polarization direction of the incident light [15]. Thus, the normalized Raman intensities of the G-band and the 2D-band measured in out-of-plane configuration with respect to that measured in in-plane configuration, and , respectively, were expected to exhibit cos2θ-dependence. Experimental data, shown in Figure 3b,c, for the G-band and the 2D-band as a function of θ, agreed quite well with cos2θ-dependence (the black solid line) as expected.Figure 3


Polarized Raman spectroscopy with differing angles of laser incidence on single-layer graphene.

Heo G, Kim YS, Chun SH, Seong MJ - Nanoscale Res Lett (2015)

Polarized Raman spectra of a monolayer graphene on a TEM grid in the backscattering geometry. (a) Polarized Raman spectra of a monolayer graphene on a TEM grid in the backscattering geometry with differing angles (θ) of the laser incidence. Excitation laser wavelength was 532 nm. The black curves are Raman spectra measured with in-plane configuration and the red ones measured with out-of-plane configuration. (b, c) Normalized Raman intensity of the G-band (b) and the 2D-band (c) in out-of-plane configuration with respect to that in in-plane configuration as a function of laser incidence angle, respectively. The black lines represent cos2θ.
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Related In: Results  -  Collection

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Fig3: Polarized Raman spectra of a monolayer graphene on a TEM grid in the backscattering geometry. (a) Polarized Raman spectra of a monolayer graphene on a TEM grid in the backscattering geometry with differing angles (θ) of the laser incidence. Excitation laser wavelength was 532 nm. The black curves are Raman spectra measured with in-plane configuration and the red ones measured with out-of-plane configuration. (b, c) Normalized Raman intensity of the G-band (b) and the 2D-band (c) in out-of-plane configuration with respect to that in in-plane configuration as a function of laser incidence angle, respectively. The black lines represent cos2θ.
Mentions: Figure 3a shows the Raman spectra for different angles of laser incidence onto the single-layer graphene on a TEM grid in the backscattering geometry, where the black lines and the red lines correspond to the Raman spectra taken in (VV) and (HH) polarization configurations, respectively. In the (HH) polarization configuration, the entire electric field vector of the incident light cannot interact with the electrons on the graphene whereas it can interact with them in the (VV) polarization configuration, as shown in Figure 1b. In fact, only the projected component of the electric field vector of the incident light onto the graphene plane can effectively contribute to Raman scattering process as illustrated in Figure 1b. This is exactly the same situation as the polarized Raman scattering on single isolated CNT, where the Raman intensities of the G-band and the RBM of the CNT exhibited approximately cos2α-dependence in which α is the angle between the CNT axis and the polarization direction of the incident light [15]. Thus, the normalized Raman intensities of the G-band and the 2D-band measured in out-of-plane configuration with respect to that measured in in-plane configuration, and , respectively, were expected to exhibit cos2θ-dependence. Experimental data, shown in Figure 3b,c, for the G-band and the 2D-band as a function of θ, agreed quite well with cos2θ-dependence (the black solid line) as expected.Figure 3

Bottom Line: In an out-of-plane configuration, the angle between the polarization vector and the graphene plane is the same as the angle of laser incidence (θ).The normalized Raman intensity of the G-band measured in the out-of-plane configuration, with respect to that in the in-plane configuration, was analyzed as a function of θ.The normalized Raman intensity showed approximately cos(2) θ-dependence up to θ = 70°, which can be explained by the fact that only the electric field component of the incident and the scattered photon in the out-of-plane configuration projected onto the graphene plane can contribute to the Raman scattering process because of the perfect confinement of the electrons to the graphene plane.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Chung-Ang University, Seoul, 156-756 Republic of Korea.

ABSTRACT
Chemical vapor deposition (CVD)-grown single-layer graphene samples, transferred onto a transmission electron microscope (TEM) grid and onto a quartz plate, were studied using polarized Raman spectroscopy with differing angles of laser incidence (θ). Two different polarization configurations are used. In an in-plane configuration, the polarization direction of both incident and scattered light is parallel to the graphene plane. In an out-of-plane configuration, the angle between the polarization vector and the graphene plane is the same as the angle of laser incidence (θ). The normalized Raman intensity of the G-band measured in the out-of-plane configuration, with respect to that in the in-plane configuration, was analyzed as a function of θ. The normalized Raman intensity showed approximately cos(2) θ-dependence up to θ = 70°, which can be explained by the fact that only the electric field component of the incident and the scattered photon in the out-of-plane configuration projected onto the graphene plane can contribute to the Raman scattering process because of the perfect confinement of the electrons to the graphene plane.

No MeSH data available.


Related in: MedlinePlus