Seminars & Lectures
| * TITLE | Colossal flexoresistance effect via robust nanoscale flexoelectricity | ||||||
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| * DATE / TIME | 2020-06-24, 14:00-15:00 | ||||||
| * PLACE | #503, Hogil Kim Memorial Bldg. & ZOOM Webinar | ||||||
| * ABSTRACT | |||||||
| Flexoelectricity describes the generation of electric polarization by strain gradients in every dielectric. This universal effect is inversely proportional to the length scale, thereby promising novel, enhanced functionalities at the nanoscale. Despite its significance, however, it has been challenging to quantitatively characterize flexoelectricity at the nanoscale. In this talk, I will first demonstrate a general methodology for characterizing flexoelectricity at the nanoscale via quantum tunneling [1]. This reveals that flexoelectric coefficients remain almost unchanged over a wide range of strain gradients, i.e., from 10 –1 m –1 to 10 7 m –1 . Furthermore, I will show that this robust flexoelectricity enables damage-free exposure of dielectrics to strong static fields, leading to colossal control of conductivity [2]. Applying strain gradients with an atomic force microscope tip polarizes an ultrathin film of an archetypal dielectric via flexoelectricity, which in turn generates non-destructive, strong electrostatic fields. When the applied strain gradient exceeds a certain value, the dielectric suddenly becomes highly conductive, yielding at least 10 8 -fold decrease in room-temperature resistivity. I explain this phenomenon, which we call the colossal flexoresistance, based on the abruptly increased tunnel conductance in ultrathin dielectrics under giant strain gradients. This work extends the scope of electrical control in solids, and inspires further exploration of dielectric responses to strong electromechanical fields. 1 S. Das et al., Nature Commun. 10, 537 (2019) 2 S. M. Park et al., Nature Commun. 11, 2586 (2020) |
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