Real time observation of mechanically triggered piezoelectric current in individual ZnO nanobelts

The detection of piezoelectric current in one-dimensional semiconductor materials has been a controversial issue due to the possibility of charge annihilation at nanoscale dimensions. We report here, the mechanically triggered electrical current in uniaxially compressed individual ZnO nanobelts under no applied bias. The measurements were carried out in situ by using a transmission electron microscope. In contrast to the bending mode, the magnitude of the electrical current increased with the increase of uniaxial compression, which indicates the load-mode dependency of the detected current. The flow of electrical current through the ZnO nanobelts under applied stress was explained based on the separation of ionic charges along the two ends of the nanobelts due to the applied compressive force. The charge separation is expected to induce an internal electric field inside the nanobelt and facilitate the movement of free charge carriers through the nanobelt. Due to the separation and accumulation of charges, the metal-semiconductor system becomes forward biased when contact is established, leading to the flow of electrons through the Schottky barrier.