Piezotronic effect enhanced Schottky-contact ZnO micro/nanowire humidity sensors

A ZnO micro/nanowire has been utilized to fabricate Schottky-contacted humidity sensors based on a metal–semiconductor–metal (M–S–M) structure. By means of the piezotronic effect, the signal level, sensitivity and sensing resolution of the humidity sensor were significantly enhanced when applying an external strain. Since a higher Schottky barrier markedly reduces the signal level, while a lower Schottky barrier decreases the sensor sensitivity due to increased ohmic transport, a 0.22% compressive strain was found to optimize the performance of the humidity sensor, with the largest responsivity being 1, 240%. The physical mechanism behind the observed mechanical–electrical behavior was carefully studied by using band structure diagrams. This work provides a promising way to significantly enhance the overall performance of a Schottky-contact structured micro/nanowire sensor.