Undoped zinc oxide (ZnO) thin films with various thicknesses were deposited onto glass substrates by advanced spray pyrolysis technique by varying the volume of spray solution. All the films were deposited at 473 K substrate temperature. These samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques, respectively. The X-ray diffraction analysis reveals that film growth is preferentially along (0 0 2) plane and thickness independent. All films exhibit hexagonal wurtzite structure, however, noticeable change is observed in crystallite size. An enhancement in the grain size with increase in film thickness was observed from the SEM studies. A two probe resistivity measurements exhibit decrease in resistivity with increase in film thickness. The response of ZnO samples toward H2S gas has been investigated at different operating temperatures and gas concentrations. Highest sensitivity was obtained for the film with 135 nm film thickness at 20 ppm H2S concentration when operating temperature is 573 K. The observed variation in sensitivity is related to the change in grain size with variation in film thickness.
Bibliographical noteFunding Information:
Authors thankfully acknowledge financial support received from the University Grants Commission (UGC), New Delhi, India in the frame work of major research project [UGC Reference No. 33-399/2007 (SR)]. Authors are also thankful to the Department of Science and Technology (DST), Government of India, New Delhi for financial support through DST-PURSE scheme. This work is partially supported by the Human Resources Development of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Knowledge Economy (No.: 20124010203180).
- HS sensing
- Spray pyrolysis
- Thin films