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°C. We prepared three types of sensors using a β‐Ga2O3 single crystal in a sandwich structure with Pt pad electrodes and β‐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°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.

Surface and morphological studies of pure and Sb doped thin film gas sensors AIP Conf.In this article, we report the fabrication of an oxygen sensor based on gallium oxide thin films prepared by the chemical solution deposition method. The oxygen sensing properties of the device ͑response and recovery time, sensitivity, stability͒ were investigated at high temperature ͑1000°C͒. Attention was paid to the influence of the annealing conditions on the oxygen sensing properties of the Ga 2 O 3 thin film sensor. Surface morphology of thin film samples, studied by using atomic force microscopy measurements, shows that there are grain size differences due to various annealing conditions ͑temperature and time period͒. The results show that the annealing conditions affect not only the grain size and surface structure of Ga 2 O 3 thin films but also the oxygen sensing properties of the material. It was shown that the response time of the Ga 2 O 3 sensors decreased when the annealing temperature and annealing time were increased. The sensitivity of the sensor devices it is also affected when the annealing parameters are changed. The response time at 1000°C was 12 s for the Ga 2 O 3 film sensor annealed at 1000°C for 14 h.

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Manganese oxide films for lithium secondary batteries were prepared using a reactive evaporation method. The Mn metal in the crucible suffers severe oxidation during the reactive evaporation process, during which its deposition rate deteriorates with increasing deposition run. So it is difficult to maintain the stoichiometry of films from run to run. To prevent deteriorations, a quartz ampoule has been installed at the bottom of the Mn crucible, which isolated successfully the Mn evaporant from incoming oxygen atoms. It improved the reproducibility of film composition because of stabilizing of the deposition rate. The performance of quartz ampoule was compared with that of Mo separator and stainless steel (SUS) cell.

Manganese oxide films for lithium secondary batteries were prepared using a reactive evaporation method. Mn was evaporated from a molybdenum boat by resistive heating and deposited on a glass slide under oxygen atmosphere. These films were examined with x-ray photoelectron spectroscopy (XPS) and x-ray diffraction. The Mn oxide films with a wide valency of Mn were prepared in this study. A rapid change of the back pressure was found as the deposition of Mn was started. This implies that Mn atoms start to react with O2. This means that in situ detection of reactive evaporation process can be utilized.