We have studied the effect of subsequent gamma (γ) irradiation on the absorption spectra and the optical energy gap of ZnO thin films doped with Li (ZnO:Li). The optical transmission (T) and optical reflection (R) in the wavelength range 190~800 nm of films deposited at 300 °C on sapphire, MgO or quartz substrates were measured. The dependence of the absorption coefficient α on photon energy hν was determined as a function of γ -doses. The films show direct allowed interband transition that influenced by the gamma doses. Both the optical energy gap opt g E and the absorption coefficient (α) were found to be γ -dose dependent. The results can be discussed on the basis of γ-irradiation-induced defects in the film and on the film structure. The absorption coefficient exhibits exponential dependence on photon energy obeying Urbach's rule in the absorption edge.

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