Transition from p-type to n-type semiconductor in V₂O₅ nanowire-based gas sensors: Synthesis and understanding of the sensing mechanism
To Thi Nguyet, Lai Van Duy, Nguyen Cao Nam, Do Quang Dat, Hugo Nguyen, Chu Manh Hung, Nguyễn Văn Duy, Nguyễn Đức Hòa
Abstract
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.