Physica B 302–303 (2001) 59–63 Studies on structural, optical and electrical properties of boron doped zinc oxide films prepared by spray pyrolysis technique B.J. Lokhande a , P.S. Patil a , M.D. Uplane b, * a Thin Film Physics Laboratory, Department of Physics, Shivaji University, Kolhapur 416004, India b Department of Electronics, Shivaji University, Kolhapur 416004, India Abstract Boron doped and undoped zinc oxide (ZnO) thin films were prepared by pyrolytic decomposition of methanolic solution of zinc acetate onto glass substrates. The structural properties of the films were studied by using X-ray diffraction. The results show that both the boron doped and undoped films exhibit hexagonal wurtzite structure with strong c-axis orientation as evidenced by X-ray diffraction patterns. The crystallite size wanes with increasing doping concentration. The electrical resistivity studies were carried out using the four-probe method. It is found that the films with 0.8 wt% boron doping concentration attains the lowest resistivity (10 4 O m), whereas for higher and lower doping concentrations resistivity increases. The thermoelectric power studies showed that the doped and undoped films exhibit n-type conductivity, optical studies revealed that with increase in doping concentration the transmittance of the film increases in the wavelength range 400–600 nm. The optical absorption data were used to determine band gap energy and it is found to be 3.22 eV for undoped ZnO films and 3.32 for boron doped films. # 2001 Elsevier Science B.V. All rights reserved. Keywords: Spray pyrolysis; Zinc oxide; Non-aqueous medium; Boron doping Introduction There is an increasing interest in zinc oxide based coatings in science and technology due to the potential applications in thermoelectric and gas sensitive devices, transparent electrodes in optoelectronic devices, selective surfaces, piezo- electric devices and acoustic wave transducers [1– 6]. In the last decade, many authors have reported results of thin films prepared using various techniques, such as spray pyrolysis, DC and ion beam magnetron sputtering, reactive evaporation, RF sputtering and chemical vapour deposition [7– 10]. Most of the processes described in the literature were not ideally suited for the produc- tion of large area coatings. The spray pyrolysis technique is well suited for large area coatings. Additionally it is simple and inexpensive. Joseph et al. [11] and Paraguay et al. [7] prepared ZnO thin films by the spray pyrolysis technique through an aqueous medium. XRD results showed that the films were polycrystalline with preferred orienta- tion along (0 0 2) plane [7–11]. However, ZnO films prepared by Lee and Lin through a non-aqueous medium exhibited strong orientation along (0 0 2) plane [12]. The variation in crystalline size affects *Corresponding author. Tel.: +91-0231-692508; fax: +91- 0231-691533. E-mail address: uplane@pn3.vsnl.net.in (M.D. Uplane). 0921-4526/01/$ - see front matter # 2001 Elsevier Science B.V. All rights reserved. PII:S0921-4526(01)00405-7