Journal Article

Colossal flexoresistance in dielectrics

Park, Se Young, Noh, Tae Won, Tsymbal, Evgeny Y., Chen, Long-Qing, Lee, Han Gyeol, Wang, Bo, Park, Sung Min, Ko, Eun Kyo, Suh, Dongseok, Lee, Daesu, Kim, Jeong Rae, Das, Saikat, Tao, Lingling, Paudel, Tula, Park, Nahee

2020

Overview

Dielectrics have long been considered as unsuitable for pure electrical switches; under weak electric fields, they show extremely low conductivity, whereas under strong fields, they suffer from irreversible damage. Here, we show that flexoelectricity enables damage-free exposure of dielectrics to strong electric fields, leading to reversible switching between electrical states—insulating and conducting. Applying strain gradients with an atomic force microscope tip polarizes an ultrathin film of an archetypal dielectric SrTiO 3 via flexoelectricity, which in turn generates non-destructive, strong electrostatic fields. When the applied strain gradient exceeds a certain value, SrTiO 3 suddenly becomes highly conductive, yielding at least around a 10 8 -fold decrease in room-temperature resistivity. We explain this phenomenon, which we call the colossal flexoresistance, based on the abrupt increase in the tunneling conductance of ultrathin SrTiO 3 under strain gradients. Our work extends the scope of electrical control in solids, and inspires further exploration of dielectric responses to strong electromechanical fields. Manipulating the electric state of large band gap dielectrics without any damage is quite challenging. Here, the authors demonstrate by mechanically introducing strain gradients that large electric fields are generated via flexoelectric interactions, resulting in a reversible Zener breakdown in SrTiO 3 , changing the resistivity by 10 8 .

• Publisher: Nature Publishing Group UK,Nature Publishing Group,Nature Portfolio
• Subject: 147/136 / 147/3 / 639/766/119/995 / 639/766/119/996 / Atomic force microscopes / Atomic force microscopy / Conductance / Damage / Dielectric strength / Electric fields / Electrical resistivity / Electrostatic properties / Humanities and Social Sciences / Low conductivity / multidisciplinary / Resistance / Room temperature / Science / Science (multidisciplinary) / Strain / Strontium titanates / Switches / Thin films