Manifestation of a size effect in the behavior of the intrinsic absorption edge of nanostructured polycrystalline zinc oxide thin films

We have studied the behavior of the intrinsic absorption edge in zinc oxide thin films in the temperature range 80–300 K. We have observed that the intrinsic absorption edge in films with crystal sizes of ≈45 nm or larger is described by the empirical Urbach’s rule, while in films with crystallite sizes of ≈15 nm, it is described by a modified Urbach’s rule. We have calculated the effective frequency of phonons taking part in formation of the absorption edge. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 275–277, March–April, 2007.