The band gap is usually measured by the DRS or Absorption spectrum, and Raman for characterization of materials sturcture. I want to know whether the energy gap of semiconductors can be obtained from the Raman characteristic peak, and How? Thank you in advance.
Band gap is "optical" (from UV to visible to near-IR range, depending on material) band gap of electronic transitions. Raman effect comes from inelastic scattering of "optical" (often, UV or visible or near-IR depending on instrument) radiation due to molecular or lattice vibrational transitions. So you cannot directly probe band gap by looking at Raman peaks (i.e., if you can, it would be an indirect correlation that is specific to certain molecules and not generalizeable for all cases).
Band gap is "optical" (from UV to visible to near-IR range, depending on material) band gap of electronic transitions. Raman effect comes from inelastic scattering of "optical" (often, UV or visible or near-IR depending on instrument) radiation due to molecular or lattice vibrational transitions. So you cannot directly probe band gap by looking at Raman peaks (i.e., if you can, it would be an indirect correlation that is specific to certain molecules and not generalizeable for all cases).
please check the attached file and I hope to be useful to you
http://journals.aps.org/prb/abstract/10.1103/PhysRevB.83.125307
If you were to say the common band gap range is 0.5 to 5 eV, then the wavenumber range corresponding to that would be about 4000 to 40000 cm^-1. So you can see that the range for optimical band gap does not really overlap the vibrational range (4000 cm-1 downwards. It's really more like 1000 cm-^-1 and below for semiconductors but also for small molecules with heavy atoms.
As I wrote earlier, this doesn't mean there can't be indirect links between Raman & optical band gap. See for example the attached paper on Arxiv.org. This paper shows that there are two correlations at play: the correlation between the 2D & G bands of graphene in Raman vs. strain of the graphene (see Figures 2 and 3), and also the correlation between strain and band gap (see Figures 4 and 5). In such case, the two correlations are linked by the "strain" parameter so that you can indirectly probe the optical band gap change with Raman shift frequency information -- but you would need experimental data to come up with that relationship in the first place.
So in short, since there is no direct relationship between optical band gap and Raman, it's case-by-case. If you were to disclose your system of interest (whether it be semiconductor, graphene, carbon nanotube, molecular crystals) then people in this forum may be able to help you more.
Article Resonant Raman scattering in nanocrystalline thin CdS film
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