Effect of flexoelectricity on a bilayer molybdenum disulfide Schottky contact

Molybdenum disulfide (MoS2), as a representative two-dimensional material, has distinctive physical and mechanical properties, especially in a bilayer form. Here, we conduct a study on the effect of out-of-plane flexoelectricity on a fabricated bilayer MoS2 Schottky contact via the Conductive Atomic Force Microscope (CAFM). The induced polarization in the sample under the tip force, which is entirely from the flexoelectric mechanism due to the absence of out-of-plane piezoelectricity in terms of the molybdenum-to-sulfur bond symmetry, changes the barrier height of the formed Schottky contact between the bilayer MoS2 and Au electrode. According to the Hertzian contact theory and the modified current equation of the classical thermionic emission theory, the relationship between the strain gradient and the effective barrier height ϕBp is quantitatively presented. The out-of-plane flexoelectric coefficients of the bilayer MoS2 are thus evaluated as f3333=0.4758 nC/m and f3113=f3223=0.2867 nC/m.