GAS SENSITIVITY OF SPUTTERED METAL OXIDE THIN FILMS

Abstract

Copper Oxide (CuO) and Zinc Oxide (ZnO) thin films were deposited on conductive glass substrates using DC reactive sputtering for gas sensor applications. Argon and Oxygen gases have been used as sputtering gas and reactive gas, respectively. For CuO thin films the sputtering pressure and the substrate temperature were increased from 6 to 8.5mbar and from 70 to 192°C, respectively. All the synthesized films contain single phase o f CuO in this range o f pressure and substrate temperature. The crystallite sizes vary from 9.03 to 22.47 nm as estimated by Scherrer formula. The crystallites favoring perpendicular orientations dominate at higher deposition pressures due to higher deposition rates. Due to smaller crystallite sizes, the film deposited at 192°C under 8.5mbar pressure provides gas sensitivity as high as 19.26 after keeping 10 minutes in C02 gas at room temperature. The sample fabricated at 192°C and 9 mbar indicates a sharp drop o f C 02 gas sensitivity from 3.67 to 0.84 at operating temperature 75°C. All these samples are not sensitive to N2 gas according to cross-sensitivity measured in N2 gas. Zinc Oxide thin films have been synthesized in the deposition temperature range from 130 to 153°C at chamber pressure of 8.5mbar for 18 hours. The structure of the films determined by means of the X-Ray diffractometer (XRD) at University of Peradeniya, indicates that the Zinc Oxide single phase bah be ibhrieatsd in this BubfltfRte tempemtnre ran g e3 The sensitivity of the films synthesized at substrate temperature of 130°C is 2.17 in the presence of C02 gas at the measuring temperature 100°C. .