# Evaluation of band gap from transmittance

How can I evaluate the band gap of my ZnO thin film.

Thickness=d=80 nm I’m aware of alpha=-1/d*log(T) But I can’t fit a line to my data. And: How can I smoothen my data on about 346 nm? Do you have any other idea for calculation of band gap from Transmittance and Absorbtion of light by thin films?

h=4.13566733e-15;            %# eV.s
c=299792458;                 %# m/s
%# landa in (nm)
nu=c./(landa*1e-9);          %# 1/s
alpha=-1/(50e-7)*log(T50);   %# 1/cm
E=h*nu;                      %# eV
Y=alpha.^2;
plot(E,Y);


Data: 80.txt

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""have two array lamda Vs Transmittance (T)"" What is this "array"? Do You mean plots? Why two of them? – Georg Apr 23 '11 at 10:05
Data updated... – Abolfazl Apr 23 '11 at 12:42