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Fig. 4. (Color online) (a) Schematics of the potential energy profiles across SrTiO3 (STO) with increasing flexoelectric polarization. At the critical polarization Pc, the tunnel barrier becomes triangular. (b) Measured tunnel current–voltage (IV ) curves across the nine unit cell-thick STO film for three representative strain gradient (∂ut/∂x3) values. (c) The rectification ratios |I+V /IV | of the measured tunnel current as a function of ∂ut>/∂x3. With increasing ∂ut>/∂x3, the tunnelling I-V curves become more asymmetric in the yellow regime below ∂ut>/∂x3 = 1.56 × 107 m−1, but more symmetric in the blue regime. (d) The simulated |I+V /IV| at V = 0.2 V as a function of barrier-asymmetry, defined as φ2φ1. Panels (a) – (d) are reproduced with permission from Das et al., Nat. Commun. 10, 537 (2019). Copyright 2019 Author(s), licensed under a Creative Commons Attribution 4.0 License.
New Phys.: Sae Mulli 2021;71:808~813