Mechanical Control of Quantum Tunneling and its Implication for Nanoscale Flexoelectricity

Flexoelectricity refers to a coupling between electrical polarization and strain-gradient. This electromechanical phenomenon is allowed by all material symmetry and is most profound at the nanoscale. Nanoscale flexoelectricity enables functional control of ferroelectric polarization/domain configuration, photovoltaic response, and defect distribution in oxide thin films. It also holds the potential for lead-free micro- and nano-electromechanical device applications. Accordingly, flexoelectricity has emerged as a field of active experimental and theoretical research. One of the pressing challenges, however, is developing a means to characterize flexoelectricity at the nanoscale. To this end, we studied quantum tunneling through an ultra-thin dielectric film as a function of mechanically-induced flexoelectric polarization. The tunneling transport exhibits a systematic change with polarization, which we attribute, based on the WKB modeling to flexoelectric polarization-driven modification of the tunneling barrier. Furthermore, we discuss how this mechanical approach enables quantifying the flexoelectric coefficient at the nanoscale.