Probing substrate influence on graphene by analyzing Raman lineshapes
© Huang et al.; licensee Springer. 2014
Received: 14 November 2013
Accepted: 19 January 2014
Published: 7 February 2014
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.
KeywordsSubstrate influence Graphene Raman lineshapes Voigt fitting
Graphene has many unique and novel electrical and optical properties [1–3] because it is the thinnest sp2 allotrope of carbon arranged in a honeycomb lattice. Recent studies indicate that the remarkable carrier transport properties of suspended graphene with respect to supported graphene include temperature transport, magnetotransport, and conductivity [4–6]. The phonon modes of graphene and their effects on its properties due to the dopants and defects' effects are also different between suspended and supported graphene. These effects on its properties can be studied by Raman spectroscopy [7–9]. Raman spectroscopy has been extensively used to investigate the vibration properties of materials [10–13]. Recently, characterizing the band structure of graphene and the interactions of phonons has been applied as the powerful study method [14–18]. With the different effects influenced by doping and substrate, charged dopants produced by residual photoresist in the fabrication process are possibly induced by the deposition and also affect the substrate. According to relevant studies [19, 20], the properties of metallic particles on graphene used as an electrode in graphene-based electronic devices can be understood clearly and suspended graphene is suitable to use to understand the effect of charged dopants on the substrate. In our previous works [21, 22], we used polarized Raman spectroscopy to measure the strain effect on the suspended graphene. We fitted the spectra with triple-Lorentzian function and obtained three sub-2D peaks: 2D+, 2D-, and 2D0. In another work, we observed three sub-G peaks: G+, G-, and G0. The property of intensity of G+, G is similar as 2D+ and 2D peaks. The linewidth analysis with data fitting into pure Lorentzian and Voigt profiles had been applied two-photon transitions in atomic Cs [23, 24], because of its elastic motion of atomic structures. The Voigt profile, a convolution of a Lorentzian and a Gaussian, is used to fit these Raman spectra of graphene.
In this work, the supported and suspended graphene were both fabricated by micromechanical cleavage, and then, they were identified as monolayer graphene by Raman spectroscopy and optical microscopy. The Raman signals of suspended and supported graphene can be measured and analyzed by probing the graphene surface which contains them. The peak positions of G band, the I2D/IG ratio, and bandwidths of G band fitted with Voigt profile are obtained with the Raman measurements. Under our analysis, details about the effects of charged impurities on the substrate can be realized. About the strain effect or doping effect on graphene, some possible broadening mechanisms may still be responsible for deforming it, so we considered the Gaussian profile necessary.
Results and discussion
Based on the data fitting results, the analysis of measured point across the graphene surface, the bandwidths of Gaussian profiles and Lorentzian profiles given by Voigt fitting is presented in Figure 4a,b. The horizontal axis is expressed as the mapping points of the area which contains supported (edge area) and suspended graphene (center area).
Spectroscopic investigation on graphene of the interaction between phonons and electrons with the dopant or the substrate reveals a rich source of interesting physics. Raman signals of supported and suspended monolayer graphene were obtained. The peak positions of G bands, and I2D/IG ratios, and bandwidths of G bands fitted with Voigt profiles were obtained under our analysis, and their different performances of suspended and supported graphene can be used to demonstrate the substrate influences and doping effects on graphene. The Gaussian bandwidths of those separated from Voigt profiles provide a new method to study the influence of the substrate and doping effect on graphene.
We wish to acknowledge the support of this work by the National Science Council, Taiwan under contact no. NSC 101-2112-M-006-006 and NSC 102-2622-E-006-030-CC3.
- Novoselov KS, Geim AK, Morozov SV, Jiang D, Zhang Y, Dubonos SV, Grigorieva IV, Firsov AA: Electric field effect in atomically thin carbon films. Science 2004, 306(5696):666–669. 10.1126/science.1102896View Article
- Geim AK, Novoselov KS: The rise of graphene. Nat Mater 2007, 6(3):183–191. 10.1038/nmat1849View Article
- Geim AK: Graphene: status and prospects. Science 2009, 324(5934):1530–1534. 10.1126/science.1158877View Article
- Bolotin KI, Sikes KJ, Hone J, Stormer HL, Kim P: Temperature-dependent transport in suspended graphene. Phys Rev Lett 2008, 101: 9.View Article
- Chen SY, Ho PH, Shiue RJ, Chen CW, Wang WH: Transport/magnetotransport of high-performance graphene transistors on organic molecule-functionalized substrates. Nano Lett 2012, 12(2):964–969. 10.1021/nl204036dView Article
- Rouhi N, Wang YY, Burke PJ: Ultrahigh conductivity of large area suspended few layer graphene films. Appl Phys Lett 2012, 101: 26.View Article
- Compagnini G, Forte G, Giannazzo F, Raineri V, La Magna A, Deretzis I: Ion beam induced defects in graphene: Raman spectroscopy and DFT calculations. J Mol Struct 2011, 993(1–3):506–509.View Article
- Sahoo S, Palai R, Katiyar RS: Polarized Raman scattering in monolayer, bilayer, and suspended bilayer graphene. J Appl Phys 2011, 110(4):044320. 10.1063/1.3627154View Article
- Cancado LG, Jorio A, Ferreira EHM, Stavale F, Achete CA, Capaz RB, Moutinho MVO, Lombardo A, Kulmala TS, Ferrari AC: Quantifying Defects in graphene via Raman spectroscopy at different excitation energies. Nano Lett 2011, 11(8):3190–3196. 10.1021/nl201432gView Article
- Wang JK, Tsai CS, Lin CE, Lin JC: Vibrational dephasing dynamics at hydrogenated and deuterated semiconductor surfaces: symmetry analysis. J Chem Phys 2000, 113(12):5041–5052. 10.1063/1.1289928View Article
- Wang HH, Liu CY, Wu SB, Liu NW, Peng CY, Chan TH, Hsu CF, Wang JK, Wang YL: Highly Raman-enhancing substrates based on silver nanoparticle arrays with tunable sub-10 nm gaps. Adv Mater 2006, 18(4):491. 10.1002/adma.200501875View Article
- Liu CY, Dvoynenko MM, Lai MY, Chan TH, Lee YR, Wang JK, Wang YL: Anomalously enhanced Raman scattering from longitudinal optical phonons on Ag-nanoparticle-covered GaN and ZnO. Appl Phys Lett 2010, 96(3):033109. 10.1063/1.3291041View Article
- Huang CH, Lin HY, Chen ST, Liu CY, Chui HC, Tzeng YH: Electrochemically fabricated self-aligned 2-D silver/alumina arrays as reliable SERS sensors. Opt Express 2011, 19(12):11441–11450. 10.1364/OE.19.011441View Article
- Ferrari AC, Meyer JC, Scardaci V, Casiraghi C, Lazzeri M, Mauri F, Piscanec S, Jiang D, Novoselov KS, Roth S, Geim AK: Raman spectrum of graphene and graphene layers. Phys Rev Lett 2006, 97(18):187401.View Article
- Malard LM, Pimenta MA, Dresselhaus G, Dresselhaus MS: Raman spectroscopy in graphene. Phys Rep 2009, 473(5–6):51–87.View Article
- Gao LB, Ren WC, Liu BL, Saito R, Wu ZS, Li SS, Jiang CB, Li F, Cheng HM: Surface and interference coenhanced Raman scattering of graphene. Acs Nano 2009, 3(4):933–939. 10.1021/nn8008799View Article
- Schedin F, Lidorikis E, Lombardo A, Kravets VG, Geim AK, Grigorenko AN, Novoselov KS, Ferrari AC: Surface-enhanced Raman spectroscopy of graphene. Acs Nano 2010, 4(10):5617–5626. 10.1021/nn1010842View Article
- Wu D, Zhang F, Liu P, Feng X: Two-dimensional nanocomposites based on chemically modified graphene. Chem-Eur J 2011, 17(39):10804–10812. 10.1002/chem.201101333View Article
- Casiraghi C, Pisana S, Novoselov KS, Geim AK, Ferrari AC: Raman fingerprint of charged impurities in graphene. Appl Phys Lett 2007, 91: 23.View Article
- Ni ZH, Yu T, Luo ZQ, Wang YY, Liu L, Wong CP, Miao JM, Huang W, Shen ZX: Probing charged impurities in suspended graphene using Raman spectroscopy. Acs Nano 2009, 3(3):569–574. 10.1021/nn900130gView Article
- Huang CW, Lin BJ, Lin HY, Huang CH, Shih FY, Wang WH, Liu CY, Chui HC: Observation of strain effect on the suspended graphene by polarized Raman spectroscopy. Nanoscale Res Lett 2012, 7(1):533. 10.1186/1556-276X-7-533View Article
- Huang CW, Shiue RJ, Chui HC, Wang WH, Wang JK, Tzeng YH, Liu CY: Revealing anisotropic strain in exfoliated graphene by polarized Raman spectroscopy. Nanoscale 2013, 5(20):9626–9632. 10.1039/c3nr00123gView Article
- Lee YC, Chui HC, Chen YY, Chang YH, Tsai CC: Effects of light on cesium 6S-8S two-photon transition. Opt Commun 2010, 283(9):1788–1791. 10.1016/j.optcom.2009.12.048View Article
- Lee YC, Chang YH, Chen YY, Tsai CC, Chui HC: Polarization and pressure effects in caesium 6S-8S two-photon spectroscopy. J Phys B-At Mol Opt 2010, 43: 23.
- Lee J, Novoselov KS, Shin HS: Interaction between metal and graphene: dependence on the layer number of graphene. Acs Nano 2011, 5(1):608–612. 10.1021/nn103004cView Article
- Frank O, Mohr M, Maultzsch J, Thomsen C, Riaz I, Jalil R, Novoselov KS, Tsoukleri G, Parthenios J, Papagelis K, Kavan L, Galiotis C: Raman 2D-band splitting in graphene: theory and experiment. Acs Nano 2011, 5(3):2231–2239. 10.1021/nn103493gView Article
- Yoon D, Son YW, Cheong H: Strain-dependent splitting of the double-resonance Raman scattering band in graphene. Phys Rev Lett 2011, 106: 15.
- Mohiuddin TMG, Lombardo A, Nair RR, Bonetti A, Savini G, Jalil R, Bonini N, Basko DM, Galiotis C, Marzari N, Novoselov KS, Geim AK, Ferrari AC: Uniaxial strain in graphene by Raman spectroscopy: G peak splitting, Gruneisen parameters, and sample orientation. Phys Rev B 2009, 79: 20.View Article
- Ni ZH, Yu T, Lu YH, Wang YY, Feng YP, Shen ZX: Uniaxial strain on graphene: Raman spectroscopy study and band-gap opening. Acs Nano 2008, 2(11):2301–2305. 10.1021/nn800459eView Article
- Chuev MA: An efficient method of analysis of the hyperfine structure of gamma-resonance spectra using the Voigt profile. Dokl Phys 2011, 56(6):318–322. 10.1134/S1028335811060097View Article
- Pagnini G, Mainardi F: Evolution equations for the probabilistic generalization of the Voigt profile function. J Comput Appl Math 2010, 233(6):1590–1595. 10.1016/j.cam.2008.04.040View Article
- Asthana BP, Kiefer W: Deconvolution of the Lorentzian linewidth and determination of fraction Lorentzian character from the observed profile of a Raman line by a comparison technique. Appl Spectrosc 1982, 36(3):250–257. 10.1366/0003702824638647View Article
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.