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(Color online) (a) Cross-sectional SEM image of the patterned substrate before SWNT synthesis and (b) plan view after synthesis. SWNTs were found suspended across the trenches, as indicated by the arrows. (c) Normalized G-band spectra from suspended SWNTs synthesized using 13C concentrations of 0% (β = 0) to 100% (β = 1) in 10% increments.
(Color online) Resonance Raman spectra (488 nm excitation) from four suspended semiconducting SWNTs with 13C concentrations β of (a) 0.2, (b) 0.4, (c) 0.6, and (d) 0.9. Each G-band was fitted using two Lorentzian lineshapes. Measured data, lineshapes, and fitted curves are shown by open circles, dashed lines and solid lines, respectively. γ is the FWHM of the G+ peak, and the inset shows the lone RBM feature observed in each spectrum.
(Color online) Average FWHM values of the G− (open circles) and G+ (solid squares) Raman peaks in suspended SWNTs as a function of 13C concentration. Solid curves are fits of the data using Eq. (1) with and for G−, and and for G+ (see text). The inset is a histogram of G+ FWHM statistics for the case β = 0.5 showing the symbols indicate statistical average and the bars indicate standard deviation.
Summary of resonance Raman spectral data obtained for isotope-mixed SWNTs, including the number of single-RBM spectra obtained for each 13C concentration (β) and the average FWHM values (γ) of the RBM, G−, and G+ features. The excitation laser wavelength was 488 nm.
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