Deposition of highly oriented ZnO films by spray pyrolysis and their structural, optical and electrical characterization B.J. Lokhande a, * , P.S. Patil b , M.D. Uplane a a Thin Film Physics Laboratory, Department of Electronics, Shivaji University, Kolhapur, India b Department of Physics, Shivaji University, Kolhapur, India Received 25 September 2001; received in revised form 10 April 2002; accepted 12 April 2002 Abstract Thin films of zinc oxide (ZnO) have been deposited onto glass substrates using a simple and inexpensive spray pyrolysis technique. A nonaqueous methanolic solution of zinc acetate was used as a spraying solution. The concentration of the solution was varied between 0.025 to 0.4 M. The films prepared at different solution concentrations were uniform and well adherent to the substrates. X-ray diffraction (XRD) studies showed that all the films were polycrystalline having hexagonal wurtzite-type crystal structure with strong orientation along (002) plane except 0.025 M, which exhibits a strong orientation in along (100) plane. The bandgap energy, electrical resistivity and thermoelectric power of the films were found to be dependent on the solution concentration. As solution concentration increases, the bandgap energy attenuates from 3.33 to 3.24 eV. The room temperature electrical resistivity was found to be vary in the range 10 2 to 10  3 V cm, whereas thermoelectric power increases from 1  10  6 to 8  10  5 V/K. All the films showed n-type conductivity as evidenced from thermoelectric power (TEP) measurement. D 2002 Published by Elsevier Science B.V. Keywords: Zinc oxide; Semiconductor; Characterization 1. Introduction The increasing use of transparent conducting oxide (TCO) films for liquid crystal display, silicon solar cells, energy windows has promoted many studies on the preparation and characterization of the less expen- sive and stable TCOs [1–6]. Materials like indium oxide, fluorine-doped tin oxide and zinc oxide (ZnO) have been used in such devices. These materials have been prepared by variety of techniques and are well described in literature. Thin films of ZnO have been prepared by a plethora of techniques that includes sol–gel [7], R.F. sputtering [8], spray pyrolysis [9] and all types of vapour deposition techniques [10,11]. Many researchers have prepared the ZnO films by spray pyrolysis techniques in aqueous medium with and without addition of alcohol [12–16]. However, very few researchers have paid attention to deposit the ZnO films through nonaqueous medium and their characterization. In the present investigation, an attempt has been made to deposit the ZnO films through nonaqueous 0167-577X/02/$ - see front matter D 2002 Published by Elsevier Science B.V. PII:S0167-577X(02)00832-7 * Corresponding author. Tel.: +91-231-692508; fax: +91-231- 691533. E-mail address: uplane@pn3.vsnl.net.in (B.J. Lokhande). www.elsevier.com/locate/matlet December 2002 Materials Letters 57 (2002) 573 – 579