Structure, microstructure and determination of optical constants from transmittance data of co-doped Zn0.90Co0.05M0.05O (M=Al, Cu, Cd, Na) films

ZnO, Zn0.95Co0.05O and Zn0.90Co0.05M0.05O (M=Al, Cd, Na, Cu) single phase films have been successfully synthesized by ultrasonic spray pyrolysis technique. Structural analysis by X-ray diffraction show that all the films have hexagonal wurtzite structure with an average crystallite size in the range of 19-25 nm. SEM analysis revealed that Cd and Na preserve the shape of nanopetals observed with ZnO or Co-ZnO films, while the doping with Al or Cu promote the formation of dense films constituted of nanorods. By the application of Levenberg-Marquardt least square method, the experimental transmittance data were fitted perfectly with the transmittance data calculated via a combination of Wemple-DiDomenico model, absorption coefficient of an electronic transition and Tauc-Urbach model. The concentration of absorbing centres N-Co and oscillator strength f of d-d transition of Co2+ ions are calculated from Smakula's formula. (C) 2014 Elsevier B. V. All rights reserved.