β-gallium oxide as oxygen gas sensors at a high temperature

Resistive oxygen sensors based on gallium oxide were fabricated in order to analyze their sensing performances (as sensitivity, response, and recovery time) in an oxygen atmosphere at 1000 degrees C. We prepared three types of sensors using a beta-Ga2O3 single crystal in a sandwich structure with Pt pad electrodes and beta-Ga2O3 polycrystalline thin films deposited by using both the sputtering technique and the chemical solution deposition method. For thin-film sensors, Pt interdigital electrodes were deposited on the surface of the films using the lift-off method. X-ray diffraction and atomic force microscopy investigations were performed to compare the structure and surface morphology of the samples. We achieved a response time of 10 s at 1000 degrees C, while the sensitivity was 1.03 for the single crystal and 1.35-1.45 for thin films. The sensing properties depend on the preparation condition of Ga2O3 devices.