Estimate the ratio of vacancies at (i) -119°C (ii) 80°C where average required to create vacancy is 1.8eV.

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written 3.0 years ago by

For Point defect (vacancy), we have the following relation

$n=N\times exp\Bigg(\dfrac{-Ev}{KT}\Bigg)\\ $

$\therefore \ \dfrac{n}{N}=e^{\dfrac{-Ev}{KT}}\\$ Using $K=1.38\times 10^{-23}\ \dfrac{J}{K}\ \ \ \ \ \ \ \ E_v=1.8\times 1.6\times 10^{-19}$ 1) For $t_1=-119^{\circ}\ C=-119+273=154\ K$ $\therefore \ \dfrac{n}{N}=\dfrac{e^{-(1.8\times 1.6\times 10^{19})}}{1.38\times 10^{-23}\times 154}=e^{-153.51}=1.4084\times 10^{-59}$ **.............(Answer)** **2) For $t_2=80^{\circ}\ C=80+273=353\ K$** $\therefore \ …

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