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【答案】应助回帖
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ll921: 金币+20, 翻译EPI+1, ★★★★★最佳答案 2012-09-23 09:46:46
Figure.Growth XXX absorption spectra. It can be found that growth XXX crystals from 1000 to 366 nm wavelength range has a low absorption coefficient (α), α to 3 cm -1 representative of the transparent region. Α increases sharply in the UV region (<366 nm), 15 cm-1.
The absorption coefficient α is a known case, the incident photon energy hv by the expression [28]:
αhν = A (hν of - EG) of 1 / n (1)
Wherein A is a constant. Exponent n value of 2,1 / 2,2 / 3 and 1/3 to allow direct, allows indirect ban on direct and indirect conversion prohibit, respectively. Previous reports in polycrystalline samples to the bandgap XXX estimated absorption edge and measuring conductivity, respectively [12, 23 and 25]. However, the authors pointed out that the type of interband transitions, and theoretical calculations of. XXX crystal growth, with n = 1/2 to give the best fit, and this means that XXX is an indirect bandgap material. Indirect transition is a transition with the help of phonons. Under this condition, from the top of the valence band to the bottom of the conduction band of the electron transfer will have a different momentum, due to the change in the wave vector. To save energy, the indirect changes may appear appropriate phonon participation. In this case, the absorption coefficient can be expressed as the following equation. |
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