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

Vanadium pentoxide (V2O5) nanowires (NWs) were grown via hydrothermal method, followed by annealing treatment at 500 degrees C in air. Morphological characterization showed that the V2O5 material consists of nanowires with a diameter of 200 nm and an average length of 2.5 mu m. The nanowires were used to make an NH3 sensor that operates at room temperature (28 degrees C) and relative humidity of 40 % RH, giving a relative response of 6.0 % to 500 ppm. The V2O5 nanowires show a change in behavior from p-type semiconductor to n-type semiconductor when the temperature exceeds 50 degrees C. The maximum response (35 %) was recorded at a working temperature of 200 degrees C (when the semiconductor behaves as an n-semiconductor) and showed good response and recovery speed over 500 ppm NH3. 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.