Improved Adhesion of Two-Dimensional Materials to Ferroelectrics from Poling

Ferroelectric materials can control mechanical strain in coupled 2D materials to induce phase transitions with applied electric field [1]. 2D flake-to-ferroelectric adhesion is crucial to device performance since it affects the efficiency of strain transfer. We discuss a framework to enhance 2D-ferroelectric adhesion through repeated ferroelectric poling. We explore this using exfoliated MoTe₂ thin flakes on structurally mixed-phase rhombohedral (R)/tetragonal (T) BiFeO₃ (BFO) ferroelectric thin films grown with a metallic La_0.7Sr_0.3MnO₃ (LSMO) bottom counterelectrode for switching. Flakes with less adhesion are less conformal to the underlying R/T-BFO stripe domains due to a competition between strain energy and adhesive force. We quantify adhesion by measuring substrate conformality before and after local out-of-plane electric-field poling with a conductive AFM probe. Local poling causes both ferroelectric switching and structural transformation between R and T phases of BFO, which contribute to enhanced substrate conformality as well as a route to on-demand nanoscale strain engineering.

[1] W. Hou et al., Nat. Nano. 14, 668 (2019)