Structure, microstructure and determination of optical constants from transmittance data of co-doped Zn0.90Co0.05M0.05O (M@Al, Cu, Cd, Na) films
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Date
2014-02-24
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Abstract
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 CoAZnO 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 NCo and oscillator strength f of d–d transition of Co2+ ions are
calculated from Smakula’s formula.