Generally, the line width (full width at half maximum) of Raman peak signifies the life time of phonon as FWHM is inversely proportional to life time. This life time may increase/decrease depending on the coupling (electron-phonon, phonon-phonon etc.,) strength (stronger/weaker).
In this case, how can we identify and differentiate the electron - phonon coupling from phonon – phonon coupling through Raman line width?
Dear Rajaji,
up to my knowledge, if you want to get a strong electron -phonon coupling.. you should use an excitation energy more than the band gap of the material. Then, the virtual level of the Raman transition will shift up to next electronic level... So you may get a good electron phonon interaction.... But if you are using excitation energy less than the band gap, the virtual state will form in between the two electronic states... then in that case phonon-phonon interaction will dominate..
But I am not very much sure whether I answered your question completely....
In case you are working with polar crystals (e.g., III-V compound semiconductors such as GaAl) then there is a coupling among plasmon modes and the LO phonons in layers below the depletion region. In fact one could use this coupling phenomena to measure the depletion region thickness. We used this for highly Si doped GaAs samples man years ago (e.g., "Plasma Etching of MBE GaAs: A Raman Scattering Study". see: B. Roughani, J. Jbara, J.T. Boyd, T.D. Mantei, and H.E. Jackson, SPIE Proceedings, "Spectroscopic Characterization Techniques for Semiconductor Technology III", ed. by O.J. Glembocki, F.H. Pollak, and F. Ponce, SPIE 946, 146 (1988). or "Raman Scattering Studies of Reactive Ion Etched MBE n-type GaAs", B. Roughani, H.E. Jackson, J.J. Jbara, T.D. Mantei, G. Hickman, C.E. Stuts, K.R. Evans, and R.L. Jones, IEEE J. Quant. Elect. 25 1003 (1989).
The distinction between electron-phonon (such as Plasmon-LO phonon coupling mode), and the phonon-phonon modes is that the frequency of the electron-phonon modes are impacted by free career concentrations, while phonon-phonon mode frequency depends on the crystal symmetry (such as band-edge 2 phonon modes).
You could see as an example the following papers we published
hello Rajaji vincent,
if the electron phonon coupling is increases what will happen to phonon lifetime? will it increase or decrease?
Hi Madhu Mitha,
As the electron-phonon coupling increase, phonon lifetime will decrease.
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