# Origin of the unusual dependence of Raman D band on excitation wavelength in graphite-like materials

Sood, AK and Gupta, Rajeev and Asher, SA (2001) Origin of the unusual dependence of Raman D band on excitation wavelength in graphite-like materials. In: Journal of Applied Physics, 90 (9). pp. 4494-4497.

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## Abstract

We have revisited the still unresolved puzzle of the dispersion of the Raman disorder-induced $D$ band as a function of laser excitation photon energy $E_L$ in graphite-like materials. We propose that the $D$ mode is a combination of an optic phonon at the $K$ point in the Brillioun zone and an acoustic phonon whose momentum is determined uniquely by the double resonance condition. The fit of the experimental data with the double-resonance model yields the reduced effective mass of $0.025 m_e$ for the electron-hole pairs corresponding to the $A_2$ transition, in agreement with other experiments. The model can also explain the difference between $\omega_S$ and $\omega_{AS}$ for D and $D^\star$ modes, and predicts its dependence on the Raman excitation frequency.

Item Type: Journal Article Copyright of this article belongs to American Institute of Physics. Division of Physical & Mathematical Sciences > Physics 18 Sep 2008 10:52 19 Sep 2010 04:49 http://eprints.iisc.ernet.in/id/eprint/15904