I need to calculate the band gap of Tio2 powder can you help me to know the equation to calculate the band gap?
Dear Dalia
Peace be upon you
The band gap issue is a huge subject and can not be summarized in Q and A. Generally it may be direct and indirect energy gap. there is a theoretical equation to calculate its value.
1. In direct band gaps, the emission peaks are usually narrow but are broadened at high temperatures while the absorption specta are invariably broad.So the emission spectra should give more accurate values of lambda (max) in direct band materials.
2. The absorption spectrum of an indirect band gap material usually depends more on temperature than that of a direct material, because at low temperatures there are fewer phonons, and, therefore, it is less likely that a photon and phonon be simultaneously absorbed to create an indirect transition.As more photons are awailable at high temperatures, the absorption coefficient (alpha) increases with temperature. So if the choice is possible, one should opt for absorption spectrum for indirect band materials at high temperatures.
3. The shift of the absorption to higher energies due to doping induced band is called Burstein-Moss shift.In such cases, we should prefer absorption techniques.
It is worthy to mention also that, in semiconductor the band-gap energy tends to decrease with increasing temperature. When temperature increases, the amplitude of atomic vibrations increase, leading to larger interatomic spacing. The interaction between the lattice phonons and the free electrons and holes will also affect the band gap to a smaller extent. The relationship between band gap energy and temperature can be described by Varshni's empirical expression.
To know how could you determine the Eg Please go to my RG home page profile, there are several articles explain this matter.
Good luck
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