Light absorption in nanostructured crystalline ZnO thin films

This work is presenting some experimental results on transmissivity and absorption coefficient versus wavelength in visible and near-infrared ranges for transparent and conductive ZnO nanocrystalline thin films with thickness of 0.1 - 0.2 /spl mu/m and grain sizes of 15-20 nm. The absorption coefficient which is the measurable quantity differs in the nanocrystalline thin films as compared to that of the bulk sample, in exchange the energy band-gap which is the determinable microscopic quantity remains unchanged, its variation being connected only to the nanocrystalline structure and size lattice symmetry and particle size, up to 3-5 nm. An elementary model is considered to explain the experimental results on light absorption in ZnO nanocrystalline thin films with grain size D/sub hkl/ in the range of 15-20 nm. The proposed model applies to polycrystalline thin films 0.1-0.2 /spl mu/m with grain size larger than 5 to 7 nm.