BaZrO 3 Thin Films For Humidity Gas Sensor
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BaZrO3Thin Films For Humidity Gas Sensor XiaoXin Chen1, Michael Sorenson2,3, Clayton Butler4,5, Loren Rieth2,5, Mark S. Miller5,6, and Florian Solzbacher5,7 1 Electrical and Computer Engineering, University of Utah, 50 S. Central Campus Drive, SLC, UT, 84102 2 Electrical and Computer Engineering, University of Utah, Salt Lake City, UT, 84102 3 Univeristy of Utah, Salt Lake City, UT, 84112 4 Electrical and Computer Engineering, University of Utah, SLC, UT, 84102 5 University of Utah, SLC, UT, 84102 6 Electrical and Computer Engineering and Material Science, Univeristy of Utah, SLC, UT, 84102 7 Electrical and Computer Engineering, Material Science, and Bioengineering Department, University of Utah, SLC, UT, 84102 ABSTRACT Globally, restrictions on emissions from fossil fuel fired power plants and internal combustions engines are becoming more stringent. Microscale (MEMS) gas sensing devices are being developed to help monitor emissions and provide feedback for advanced engine controls and emission control devices. Bulk electroceramic BaZrO3 and BaZrO3 doped with Y have been found to be sensitive to H2O at high temperatures (T > 500 ∞C), where its ionic conductivity was modulated by the partial pressure of H2O. These materials have not been studied in a thin film form, therefore this research focuses on sputter deposition of undoped BaZrO3 and BaZrO3 doped with Y. This report focuses on the effects of annealing temperature and gas ambient on the properties of consistently deposited BaZrO3 and BaZr0.8Y0.2O2.9 thin films to investigate their stability at high temperatures. Use of anneals at temperatures greater than 800 ∞C will likely be used to stabilize films for use at operating temperatures greater than 500 ∞C. The materials were annealed at 800 ∞C and 1000 ∞C for 3 hours in both forming gas (H2:Ar 2%:98%) and O2. Thin films of these materials were deposited on microhotplates with interdigitated electrodes (IDEs) to measure the film conductivity. X-ray photoelectron spectroscopy (XPS) was used to measure the composition of the as deposited films, and found the films to be deficient in Ba. X-ray diffraction (XRD) was used to measure the crystal structure of the films, and indicated the as deposited films were amorphous and some crystallization occurs with annealing. Atomic force microscopy was used to examine the surface morphology of the thin films versus annealing conditions, and used to quantify RMS roughness and average particle size for the films. INTRODUCTION Microscale (MEMS) gas sensors are being developed for application in power plant and automobile exhaust gas streams in order to increase efficiency and decrease emission through improved combustion process control. This work is focused on
BaZrO3:Y thin film sensors for measuring H2O partial pressures at high temperature (T > 500 oC). Power plants operate not only at high temperatures and high pressures (P up 15 bar), thus it is imperative that sensing device be reliable at high temperatures, and in the presence of aggressive gases. Electroche
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