D-band Raman Spectra of Graphite and Single Wall Carbon Nanotubes
- PDF / 489,379 Bytes
- 6 Pages / 595 x 842 pts (A4) Page_size
- 90 Downloads / 196 Views
D-band Raman Spectra of Graphite and Single Wall Carbon Nanotubes
R. Saito , A. Grueneis , L. G. Cancado , M. A. Pimenta , A. Jorio , A. G. Souza Filho , G. Dresselhaus , and M. S. Dresselhaus Dept. of Electronic Eng., Univ. of Electro-Communications, Chofu Tokyo 182-8585 Japan; Dept. de F sica,Univ. F ederalde Minas Gerais, Belo Horizonte - MG, 30123-970 Brazil; Dept. of Physics, F rancis BitterMagnet Laboratory, Dept. of Electrical Eng. and Computer Science, Massach usetts Institute of T ec hnology , Cambridge, MA 02139-4307, USA; Dept. de F sica, Univ.F ederal do Cear a, F ortaleza -CE, 60455-900 Brazil. a
a
d
b
b
c
f
c;e
a
b
c
d
e
f
ABSTRACT
The double resonance Raman spectra of the disorder-induced D-band and some other nonzone-center phonon modes are discussed for two-dimensional (2D) graphite and to some extent for single wall carbon nanotubes (SWNTs). The phonon dispersion relations of graphite can be determined using Raman spectroscopy b y measuring the non-zone center Raman phonon frequencies in combination with theoretically determined phonon q-vectors. We report a t of the phonon dispersion relations to experimental Raman spectra which were previously observed but hav e not y et been assigned to speci c phonon branches. We found that the D-band and the G0 -band of 2D graphite consist of, respectively, two and one Raman Lorentzian peaks, while 3D graphite shows two G0 -band Lorentzian peaks. The appearance of two G0 peaks in the resonance Raman spectra of SWNTs may come from resonances of one laser line with two di erent van Hov e singularities. INTRODUCTION
Recently, eld e ect transistors based on single wall carbon nanotubes (SWNTs) have been demonstrated[1] making the characterization of one carbon nanotube on a Si surface increasingly important. Resonance Raman spectroscopy th us becomes a useful nano-technology tool, as a non-destructive, non-contact, and quick ( 1{10 min) measurement, made at room temperature and under ambient atmospheric conditions. Recently we hav e shown that micro-Raman measurements can be made on isolated SWNTs[2, 3, 4, 5]. Furthermore, the (n; m) value of an individual resonant SWNT can be assigned from its radial breathing mode (RBM) frequency !RBM, when combined with theory[2]. F or tube diameters from 1 to 2 nm, we expect di erent (n; m) v alues as !RBM changes b y 1 cm01 . Thus, the assignment of (n; m) v alues only from analysis of !RBM might hav e some ambiguity. Howev er,b y observing the resonance enhancement using a tunable laser[6], b yin v estigatingRaman-active modes b ytheir Stokes and anti-Stokes spectra[7], and b ystudying chirality-dependent Raman features at the single nanotube level, the reliability of the (n; m) assignment can be signi cantly improv ed. We rst focus our attention on the disorder-induced D-band and its second harmonic G0 -band in 2D graphite, since the double resonance process of graphite is necessary to understand the corresponding mechanism in SWNTs[8, 9]. D-BAND SPECTRA AND DOUBLE RESONANCE THEORY
The disorder-indu
Data Loading...
