Lu

500 800 1100 1400 1700 2000 RAMAN SHIFT (cnr1)

Figure 8.17. Raman spectra of (a) diamond, (b) graphite, and (c) microcrystalline graphite. The latter spectrum shows the D band at 1355cm"1 and the G band at 1580cm'1. [Adapted from R. E. Shroder, J. R. Nemanich, and T. J. Glass, Phys. Rev. B41, 3738 (1990).]

500 800 1100 1400 1700 2000 RAMAN SHIFT (cnr1)

Figure 8.17. Raman spectra of (a) diamond, (b) graphite, and (c) microcrystalline graphite. The latter spectrum shows the D band at 1355cm"1 and the G band at 1580cm'1. [Adapted from R. E. Shroder, J. R. Nemanich, and T. J. Glass, Phys. Rev. B41, 3738 (1990).]

Figure 8.18. Infrared (a) and Raman (b) spectra of solid Ceo with the lines labeled by their wavenumbers. [From A. M. Rao et al„ Science 259, 955 (1993).]

Figure 8.18. Infrared (a) and Raman (b) spectra of solid Ceo with the lines labeled by their wavenumbers. [From A. M. Rao et al„ Science 259, 955 (1993).]

is referred to as die D band. The D band has been attributed to phonons that are Raman-active because of the finite size of the microcrystals. Figure 8.19 presents a series of Raman spectra from various forms of crystalline graphite, as well as spectra from four samples of amorphous carbon with graphitic features. These spectra can be used to assess the degree of disorder and the nature of the local chemical bonding. The log-log plot of Fig. 8.20 shows how the nanocrystal size La is related to the intensity ratio /d//g of the D band to the G band. The linearity extends over two orders of magnitude, from Lt = 3 nm to L, = 300 nm. The nanocrystallite sizes for the data plotted in Fig. 8.20 had been independently determined from X-ray scattering data.

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