Improvement of ozone detection with GLAD Wo3 films

Tungsten oxide WO3 thin films were prepared by dc reactive magnetron sputtering. The GLancing Angle Deposition (GLAD) technique was implemented to transform the typical dense microstructure into an inclined columnar and porous architecture. The incident angle alpha of the sputtered particles was 0 degrees and 70 degrees leading to a column tilt angle beta of 0 degrees and 40 degrees, respectively. Conventional and inclined WO3 films were sputter deposited on a commercial hotplate system. Ozone gas was periodically injected from 0 to 220 ppb and the variation of electrical conductance of the system was measured vs. time at 250 degrees C. The conventional WO3 films exhibited a significant change of electrical conductance as a function of the ozone injection. GLAD WO3 films with a columnar angle beta=40 were even more sensitive to the ozone pulses and the speed of response or recovery was significantly enhanced. This ozone detection improvement was mainly attributed to the more porous structure of WO3 films produced by the GLAD method. (C) 2015 Elsevier B.V. All rights reserved.