Promising Piezoelectric Performance of Single Layer Transition-Metal Dichalcogenides and Dioxides

Piezoelectricity is a unique material property that allows one to convert mechanical energy into electrical one or vice versa. Transition metal dichalcogenides (TMDC) and transition metal dioxides (TMDO) are expected to have great potential for piezoelectric device applications due to their noncentrosymmetric and two-dimensional crystal structure. A detailed theoretical investigation of the piezoelectric stress (en) and piezoelectric strain (d(11)) coefficients of single layer TMDCs and TMDOs with chemical formula MX2 (where M=Cr, Mo, W, Ti, Zr, Hf, Sn and X = O, S, Se, Te) is presented by using first-principles calculations based on density functional theory. We predict that not only the Mo- and W-based members of this family but also the other materials with M=Cr, Ti, Zr and Sn exhibit highly promising piezoelectric properties. CrTe2 has the largest en and d(11) coefficients among the group VI elements (i.e., Cr, Mo, and W). In addition, the relaxed-ion e(11) and d(11) coefficients of Sn-52 are almost the same as those of CrTe2. Furthermore, TiO2 and ZrO2 pose comparable or even larger e(11), coefficients as compared to Mo- and W-based TMDCs and TMDOs. Our calculations reveal that TMDC and TMDO structures are strong candidates for future atomically thin piezoelectric applications such as transducers, sensors, and energy harvesting devices due to their piezoelectric coefficients that are comparable (even larger) to currently used bulk piezoelectric materials.