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Your second figure is a simplification of the first one, usually in the $ \Gamma $ point, but it could be any other as well. Regarding your questions: There are multiple lines in valence and conduction band because there are several allowed bands or energy eigen states. Technically there is even an infinite number of allowed bands, but usually you would ...


In any case, for undoped graphene, the Fermi level of electrons and holes are symmetric so the Fermi Energy lies at the Dirac Point, so these two definitions would be equivalent.


The conduction and valence band electron are only differed by their Wannier orbital (wave function within each unit cell), so exciting a Bloch electron from one band to another changes the Wannier orbital of the electron, for example, from a bounding orbital to an anti-bounding orbital. In the simplest 1D example of a periodic potential, exciting the ...


When you are exciting an electron from VB to CB, you normally talk in terms of transition from a state $|k\rangle$ to $|k'\rangle$ and $E(k')>E(k)$. Specifying $|k\rangle$ automatically rules out an precise determination of $|x\rangle$ as the state $|k\rangle$ is spread over the entire real space with specific weight at each point.


I found a paper titled: "A New and Simple Model for Plasma- and Doping-Induced Band Gap Narrowing" (by Ahmed Shaker and Abelhalim Zekry in the Journal of Electron Devices, Vol. 8, 2010, pp. 293-299) which has a more intuitive explanantion of why the band gap narrows. link to the paper for the lazy: A new and simple Model for Plasma and Doping and Doping ...


I think selenium was such a thing that was used for old fashioned photocopiers. The cylinder was charged electrostatically, then exposed to the image of the paper being copied. The areas exposed to light became conductive and lost their charge. The toner had the opposite charge and would the stick to the black areas. This would then be put onto a new piece ...


Yes. Whether the result is a good conductor depends on how localized electrons and holes in the respective bands are (or, saying the opposite phenomenologically: on their mobility). Their recombination time limits for how long you will have even just two charge carriers available for conduction. This tends to make such conduction very energy-inefficient ...

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