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Can anyone tell me what is the "Brus Approximation" in case of the bang gap of semiconductors?

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- Thread starter String_man
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- #1

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Can anyone tell me what is the "Brus Approximation" in case of the bang gap of semiconductors?

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malawi_glenn

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what is "bang gap" ?

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sorry !!! its just a typing mistake. You can understand what i wanna say.

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malawi_glenn

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I have never heard of Brus Approximation, is that also a typo? Can you elaborate a bit?

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Cthugha

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Brus developed a model to predict the band gap energy of nanocrystallites, quantum dots and other small spherical structures with radius R. Roughly speaking, the approach is to start with the bulk value of the energy gap, add a "particle-in-a-box" like term for electrons and holes using an effective mass approximation for the masses of both and subtracting a term, which corresponds to the Coulomb-attraction between electrons and holes. The particle-in-a-box-term scales with 1/R² and the attraction term scales with 1/R, so in small structures the 1/R²-term dominates.

However this approach uses effective masses, which do not depend on the size of the structure. Therefore the results are ok for structures of intermediate size, but are rather wrong for very small structures.

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