Dynamic adhesion of 2D materials to mixed-phase BiFeO3 structural phase transitions.

Two-dimensional materials, such as transition metal dichalcogenides, have generated much interest due to their strain-sensitive electronic, optical, magnetic, superconducting, or topological properties. Harnessing control over their strain state may enable new technologies that operate by controlling these materials' properties in devices such as straintronic transistors. Piezoelectric oxides have been proposed as one method to control such strain states on the device scale. However, there are few studies of how conformal 2D materials remain on oxide materials with respect to dynamic applications of the strain. Non-conformality may lead to non-optimal strain transfer. In this work, we explore this aspect of oxide-2D adhesion in the nanoscale switching of the substrate structural phase in thin 1T′-MoTe2 attached to a mixed-phase thin-film BiFeO3 (BFO), a multiferroic oxide with an electric-field induced structural phase transition that can generate mechanical strains of up to 2%. We observe that flake thickness impacts the conformality of 1T′-MoTe2 to structural changes in BFO, but below four layers, 1T′-MoTe2 fully conforms to the nanoscale BFO structural changes. The conformality of few-layer 1T′-MoTe2 suggests that BFO is an excellent candidate for deterministic, nanoscale strain control for 2D materials. [ABSTRACT FROM AUTHOR]