Strongly enhanced electromechanical coupling in atomically thin transition metal dichalcogenides

Flexoelectricity in thin films has emerged as an effective electromechanical response owing to appealing scaling law and universal existence. However, current studies show limited out-of-plane converse flexoelectric effect (CFE) of ultra-thin transition metal dichalcogenides (TMDs) when compared their conventional in-plane piezoresponse. Here, we report flexoresponse atomically TMDs such molybdenum disulfide (MoS2) tungsten diselenide (WSe2) which exceeds intrinsic piezoresponses. Our piezoresponse force microscopy (PFM) measurements revealed strongly enhanced CFE the MoS2 WSe2 than bulk counterpart (∼700% enhancement MoS2, ∼400% WSe2). We observed anomalous reduction monolayer structure attributed a puckering deformation. By inducing built-in tension reduce puckering, estimated be 8.14 pm/V, highest among TMDs.