Transition from p-type to n-type semiconductor in V₂O₅ nanowire-based gas sensors: Synthesis and understanding of the sensing mechanism

Vanadium pentoxide (V 2 O 5 ) nanowires (NWs) were grown via hydrothermal method , followed by annealing treatment at 500 °C in air. Morphological characterization showed that the V 2 O 5 material consists of nanowires with a diameter of 200 nm and an average length of 2.5 μm. The nanowires were used to make an NH 3 sensor that operates at room temperature (28 °C) and relative humidity of 40 % RH, giving a relative response of 6.0 % to 500 ppm. The V 2 O 5 nanowires show a change in behavior from p-type semiconductor to n-type semiconductor when the temperature exceeds 50 °C. The maximum response (35 %) was recorded at a working temperature of 200 °C (when the semiconductor behaves as an n-semiconductor) and showed good response and recovery speed over 500 ppm NH 3 . The performance of the sensor was studied and a sensing mechanism that takes into account the change of majority charge carriers in the semiconductor was hypothesized.