Investigation of Deposition Parameters of Micro/Nanorod ZnO Thin Films with Ultrasonic Spray Pyrolysis Method

Abstract

ZnO thin films were deposited on glass substrate by ultrasonic spray pyrolysis method in two steps: i) different substrate temperatures (between 300–500 °C, step by 50 °C) and ii) different solution molarities (between 0.05 M – 0.25 M, step by 0.05 M). X-ray diffraction studies showed that ZnO samples have hexagonal structure with (002) preferred direction. However, preferred orientation decreased for 450 °C and 500 °C substrate temperatures. Surface morphology of ZnO samples completely changed as hexagonal shaped microrods after 400 °C. ZnO nanorods with hexagonal shape grew for 0.05 M. Composition ratio ([Zn]/[O]) of the samples decreased from 1.07 to 1.01 depending on substrate temperature as [Zn]/[O] ratio increased from 1.04 to 1.09 with increasing molarity. A sharp ultraviolet luminescence was observed at ~380 nm for high substrate temperature and molarity values. Band gap values decreased from 3.27 eV to 3.19 eV as increasing of substrate temperature. Solution molarity was not effected significantly band gap values (3.20–3.22 eV) of the samples. Lower resistivity (1.56´10³ W-cm) and higher carrier concentration values (1.27´10¹⁵ cm^–3) was obtained for 400 °C substrate temperature and 0.15 M.