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. .