Determination the dispersion parameters and urbach tail of ZnO and ZnO:Co thin films prepared by The chemical Spray pyrolysis technique

Abstract

Undoped and Co doped ZnO samples with two different percentage of Co
content (1 %, 5 % ) were prepared by a chemical Spray pyrolysis technique.
Transmission and absorptance spectra have been recorded in the wavelength
range (300-900) nm. From The refractive index data for infinite wavelength
we have calculated single oscillator energy and dispersion energy proposed by
Wemple -DiDomenico model which was found to be decrease from (2.42 -
1.47) eV as the doping percentage increase. the optical energy gap which was
found according to Tauc model were (3.17-3.29) eV. The obtained values for
Urbach energies was found increasing from (0.757-0.902) eV upon doping