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Journal of Nanomaterials
Volume 2013 (2013), Article ID 423632, 9 pages
Research Article

Effect of Solution Spray Rate on the Properties of Chemically Sprayed ZnO:In Thin Films

1Department of Materials Science, Tallinn University of Technology, Ehitajate Tee 5, 19086 Tallinn, Estonia
2Centre for Materials Research, Tallinn University of Technology, Ehitajate Tee 5, 19086 Tallinn, Estonia

Received 14 December 2012; Accepted 1 March 2013

Academic Editor: Jie-Fang Zhu

Copyright © 2013 Merike Kriisa et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


ZnO:In thin films were grown from 100 mL of spray solution on glass substrates by chemical spray at °C using solution spray rates of 0.5–6.7 mL/min. Zinc acetate and indium(III)chloride were used as Zn and In sources, respectively, with [In]/[Zn] = 3 at.%. Independent of solution spray rate, the crystallites in ZnO:In films grow preferentially in the (101) plane parallel to the substrate. The solution spray rate influences the surface morphology, grain size, film thickness, and electrical and optical properties. According to SEM and AFM studies, sharp-edged pyramidal grains and canvas-resembling surfaces are characteristic of films grown at spray rates of 0.5 and 3.3 mL/min, respectively. To obtain films with comparable film thickness and grain size, more spray solution should be used at low spray rates. The electrical resistivity of sprayed ZnO:In films is controlled by the solution spray rate. The carrier concentration increases from  cm−3 to  cm−3 when spray rate is increased from 0.5 mL/min to 3.3 mL/min independent of the film thickness; the carrier mobilities are always lower in slowly grown films. Sprayed ZnO:In films transmit 75–80% of the visible light while the increase in solution spray rate from 0.5 mL/min to 3.3 mL/min decreases the transmittance in the NIR region and increases the band gap in accordance with the increase in carrier concentration. Lower carrier concentration in slowly sprayed films is likely due to the indium oxidation.