Inducing Exraordinarily Piezoelectric Response via Homogeneous and Heterogeneous Functionalization of a Sc2C Nanosheet, A Quantum Chemical Investigation

Piezoelectricity is pivotal for applications in micro/nanoelectromechanical (MEMS/NEMS) systems. Inducing such property into the two-dimensional Sc2CTT′ MXenes (where T and T′ are the functionalization atoms) via homogeneous and heterogeneous surface functionalization is explored. The functionalization atoms T and T′ located at the upper and lower surfaces, respectively, are identical in the case of homogeneous functionalization, while they differ in the case of heterogeneous functionalization. Upon T and T′ exchange, an additional reverse heterogeneous configuration is generated. The heterogeneous functionalization of Sc2CT2 induces an extraordinary in-plane and out-of-plane piezoelectric effect owing to symmetry breaking. Interestingly, both heterogeneous and its reverse configuration show approximately identical geometrical, energetic, and even elastic properties, but rather different piezoelectric coefficients. The obtained piezoelectric effect is more than ten times larger than the experimentally measured piezoelectricity of MoS2-monolayer. Our study suggests a way toward more efficient nanoscale piezoelectric devices based on Sc2C MXenes.