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Carbon nanotube population analysis



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APPLIED PHYSICS LETTERS 88 023109 2006 Carbon nanotube population analysis from Raman and photoluminescence intensities A Jorio C Fantini and M A Pimenta Departamento de F sica Universidade Federal de Minas Gerais Belo Horizonte Minas Gerais 30123 970 Brazil D A Heller and M S Strano Department of Chemistry Department of Chemical and Biomolecular Engineering University of Illinois at Urbana Champaign 118 Roger Adams Laboratory Box C 3 600 South Mathews Avenue Urbana Illinois 61801 3602 M S Dresselhaus Department of Physics and Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge Massachusetts 02139 4307 Y Oyama J Jiang and R Saito Department of Physics Tohoku University and CREST JST Aoba Sendai 980 8578 Japan Received 25 July 2005 accepted 11 November 2005 published online 11 January 2006 In the absence of standard single wall carbon nanotube samples with a well known n m population we provide both a photoluminescence excitation PLE and resonance Raman scattering RRS analysis that together can be used to check the calculations for PLE and RRS intensities for carbon nanotubes We compare our results with available models and show that they describe well the chirality dependence of the intensity ratio confirming the differences between type 1 and type 2 semiconducting tubes 2n m mod 3 1 and 2 respectively and the existence of a node in the radial breathing mode intensity for type 2 carbon nanotubes with chiral angles between 20 and 25 2006 American Institute of Physics DOI 10 1063 1 2162688 Large efforts are now being directed to developing synthesis or manipulation processes able to generate single wall carbon nanotubes SWNTs with well defined geometric structure i e diameter dt and chiral angle or equivalently their n m indices 1 3 Photoluminescence excitation2 4 PLE and resonance Raman spectroscopy5 7 RRS are two techniques able to nondestructively probe isolated tubes and large ensembles characterizing the result of a given synthesis or separation process giving the n m values of the samples using optical techniques Since the RRS and PLE intensities depend on the number of scatterers in the sample intensity analysis provides the population of specific n m SWNTs in the sample 8 10 However since the efficiency for the RRS and PLE processes should also depend on n m the population information cannot be extracted directly from the measured intensities but should firstly be corrected to account for the n m dependence of the RRS and PLE efficiencies 9 10 To make such corrections for the n m dependence of the RRS and PLE intensities different calculations have been performed 11 15 However due to the lack of a sample with a well known n m population there is no experimental evaluation of the accuracy of the proposed models In this paper we provide experimental results that can be used to evaluate the RRS and PLE intensity calculations We measure both RRS and PLE on a SWNT sample and we propose PLE RRS IExp should be inthat the experimental intensity ratio IExp dependent of the n m population This ratio can therefore be used to test the validity and accuracy of the calculated PLE RRS ICalc intensity ratio ICalc The RRS and PLE experiments were performed at room temperature on HiPco SWNTs in SDS suspended aqueous solution prepared as described in Ref 16 For the RRS experiments a Dilor XY triple monochromator equipped with a N2 cooled charge coupled device CCD was used and excited by ArKr Ti Sapphire and dye lasers in the range RRS 1 6 to 2 7 eV The reported data for RRS intensities IExp 6 S are related to resonances with the E22 nanotube levels For PLE experiments we used a home built n IR fluorescence spectrometer coupled to a nitrogen cooled germanium detector Edinburgh Instruments The excitation ranged between 1 55 to 3 10 eV and nanotube emission was measured between 0 89 to 1 38 eV The reported data for PLE intensities PLE S S are related to absorption at E22 and emission at E11 IExp 4 RRS PLE levels The spectral intensities IExp for RRS and IExp for PLE see Table I were evaluated from the radial breathing mode RBM RRS profile6 and from the PLE resonance profile4 8 for each n m tube The RRS intensities are calibrated by measuring the signal of nonresonant CCl4 under the same conditions The PLE intensities are calibrated by dividing the nanotube signal over the relative lamp power at all excitation wavelengths and by considering the blackbody spectrum A given PLE or RRS experimental intensity accuracy is basically related to the strength of the signal and the number of different excitation laser lines close enough in energy so that the resonance profile can be well evaluated This profile can change from tube to tube and in our case the accuracy is better than 20 When comparing the n m dependence for PLE data obtained in this paper with published data for the IExp HiPco SWNTs e g by Bachilo et al 8 the overall n m dependence is similar Some intensity differences go up to 30 of the values and these differences can be related to 0003 6951 2006 88 2 023109 3 23 00 88 023109 1 2006 American Institute of Physics Downloaded 16 Jan 2006 to 130 126 226 153 Redistribution subject to AIP license or copyright see http apl aip org apl copyright jsp 023109 2 Appl Phys Lett 88 023109 2006 Jorio et al PLE TABLE I Normalized spectral intensities IRRS Exp for RRS and IExp for PLE obtained experimentally for 22 HiPco SWNTs in SDS suspended aqueous solution RRS and PLE see Refs 6 9 and 10 for excitation laser energy and radial breathing mode frequency of each n m SWNT The n m dependent RRS ICalc PLE normalized theoretical intensities see text are also given ICalc n m IRRS Exp IPLE Exp RRS ICalc PLE ICalc n m IRRS Exp IPLE Exp RRS ICalc PLE ICalc 6 4 6 5 7 5 7 6 8 3 8 4 8 6 8 7 9 1 9 2 9 5 0 13 0 16 0 90 0 16 1 00 0 01 0 18 0 04 0 08 0 08 0 01 0 00 0 29 0 60 0 73 0 18 0 53 1 00 0 95 0 00 0 23 0 80 0 51 0 08 0 31 0 04 0 71 0 01 0 19 0 03 1 00 0 18 0 01 1 00 0 75 0 58 0 42 0 54 0 28 0 25 0 24 0 42 0 13 0 17 9 4 9 7 10 2 10 3 10 5 11 1 11 3 11 4 12 1 13 3 14 1 0 54 0 03 0 64 0 26 0 08 0 56 0 11 0 02 0 13 0 02 0 03 0 70 0 76 0 44 0 60 0 86 0 51 0 72 0 47 0 46 0 33 0 0 47 0 12 0 73 0 12 0 31 0 27 0 54 0 08 0 68 0 15 0 23 0 30 0 18 0 …


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