Strong Piezoelectricity in 3R‐MoS 2 Flakes

Distinct from conventional 2H‐MoS 2 , recently synthesized 3R‐MoS 2 exhibits a noncentrosymmetric atomic structure of the trigonal “building blocks” and, thus, remarkable piezoelectric characteristics of ultrathin 3R‐MoS 2 flakes are predicated theoretically. This paper reveals, for the first time, very high piezoelectricity in 3R‐MoS 2 flakes experimentally. Through applying mechanical stress to a 48 nm 3R‐MoS 2 flake, a high output power density of 65 mW m ‐2 is obtained and is at least one order larger than those from the corresponding monolayer MoS 2 flake. With out‐of‐plane lateral piezoresponse force microscopy technique, the two piezoelectric coefficients d 33 and d 13 are analyzed to be ≈0.9 and ≈1.6 pm V ‐1 , respectively. These piezoelectric coefficients are not apparently dependent on the flake thickness. The findings suggest that 3R‐MoS 2 is of excellent piezoelectric properties and it can be an excellent material for novel piezoelectric devices.