2D piezotronics in atomically thin zinc oxide sheets: Interfacing gating and channel width gating

Abstract

Piezotronics has potential applications in human-machine interfacing, smart skin and robotics. Here, we report the first study of two-dimensional (2D) piezotronics based on atomically thin ZnO sheets. Using the inner crystal out-of-plane potential generated by the piezoelectric polarization charges created at atomically thin ZnO surfaces under stress/strain to simultaneously modulate the metal-ZnO Schottky barrier height and the conductive channel width of ZnO, the electronic transport processes in the two-terminal devices are effectively tuned by external mechanical stimuli. Moreover, the thickness dependence of 2D piezotronics is investigated to deeply explore the inner tuning mechanism. As decreasing the thickness of ZnO from tens of nanometre to atomic scale, the gauge factor is improved to ∼2 × 108. The strain sensitivity is enhanced by over three orders of magnitude owing to the increased effective piezoelectric polarizations, which is in contrast to the conventional field effect transistor with the reduce of channel lengths. This study presents in-depth understandings about the 2D piezotronics in both interfacing gating and channel width gating in piezotronics, which fundamentally paves a way for applying 2D materials with out-of-plane piezoelectricity and semiconducting property in next generation of electromechanical nanodevices.