Investigation of gas sensor properties of vanadium oxide thin films grown by reactive DC magnetron sputtering technique

In this study, depending on the alteration in annealing temperature of the vanadium oxide sensor material, produced by the reactive DC magnetron sputtering method, the changes in the structural and gas detection performance were investigated. Vanadium oxide thin films were grown on silicon substrates by reactive DC Magnetron sputtering method. The thin films produced were annealed for 1 hour in air at 11 different temperatures between 100°C and 550°C. Structural and morphological features of the produced thin films were examined with X-ray diffraction device (XRD), field emission scanning electron microscope (FESEM). From the X-ray diffraction patterns, it was determined that the films annealed at relatively low annealing temperatures were amorphous, while the thin films annealed at 300°C and higher temperatures were found to form crystalline. Crystallite dimensions and internal stresses were calculated and compared with X-ray diffraction patterns using Scherrer method, Williamson-Hall method and Halder-Wagner method. From the FESEM images, it was observed that the morphological properties of the produced films changed depending on the annealing temperature. In order to determine the optimal operating temperature of the produced structures as a gas sensor, gas detection measurements were made for 50 ppm ammonia gas (NH3) in the temperature range of 27-287°C (300-560K). It was observed that the sensors annealed at different temperatures had different optimal operating temperatures. Among all sensors, the thin film annealed at 480°C after production showed the highest value with 104% sensitivity at 207°C operating temperature. However, some sensors gave a sensitivity comparable to the literature at 67°C an optimal operating temperature close to room temperature.