Asymmetric 2D MoS₂ for Scalable and High-Performance Piezoelectric Sensors

Abstract

Piezoelectricity in two-dimensional (2D) transition-metal dichalcogenides (TMDs) has attracted significant attention due to their unique crystal structure and the lack of inversion centers when the bulk TMDs thin down to monolayers. Although the piezoelectric effect in atomic-thickness TMDs has been reported earlier, they are exfoliated 2D TMDs and are therefore not scalable. Here, we demonstrate a superior piezoelectric effect from large-scale sputtered, asymmetric 2D MoS 2 using meticulous defect engineering based on the thermal-solvent annealing of the MoS 2 layer. This yields an output peak current and voltage of 20 pA and 700 mV (after annealing at 450 °C), respectively, which is the highest piezoelectric strength ever reported in 2D MoS 2 . Indeed, the piezoelectric strength increases with the defect density (sulfur vacancies), which, in turn, increases with the annealing temperature at least up to 450 °C. Moreover, our piezoelectric MoS 2 device array shows an exceptional piezoelectric sensitivity of 262 mV/kPa with a high level of uniformity and excellent performance under ambient conditions. A detailed study of the sulfur vacancy-dependent property and its resultant asymmetric structure-induced piezoelectricity is reported. The proposed approach is scalable and can produce advanced materials for flexible piezoelectric devices to be used in emerging bioinspired robotics and biomedical applications.

Synergetic contribution of enriched selenium vacancies and out-of-plane ferroelectric polarization in AB-stacked MoSe2 nanosheets as efficient piezocatalysts for TC degradation

“…54 Secondly, the increased density of Se vacancy defects resulted in the generation of a local asymmetric structure and inequivalent charge distribution in the crystal lattice, which further enhanced the piezoelectricity. 8,55 Thirdly, the enlarged surface area and the improved hydrophilic property enabled intimate contact between the piezocatalyst and reactant molecules. Additionally, the Se vacancy defects could provide a large quantities of exposed active edge sites and induce higher electrical conductivity, which guaranteed fast interfacial charge transfer and sufficient ROS production.…”

WS2 Monolayer for Piezo–Phototronic Dye Degradation and Bacterial Disinfection

“…In earlier reports, it was verified that the angle dependence of asymmetry and piezoelectric responses is maximum at multiple angles of 60° (defining the “armchair” direction as 0°) . Also, atomically thin 2D nanomaterials have shown their ability to withstand enormous strain up to 11% in-plane strain without fracture while demonstrating a piezoelectric effect at the nanoscale level. , It is fascinating that TMDCs do not show a piezoelectric effect in the bulk form; because of the presence of inverse orientations of adjacent atomic layers, centrosymmetry is present in their bulk form . Nevertheless, when TMDCs are thinned to a few layers–sheets, the inversion symmetry breaks and results in a piezoelectric effect .…”

Highly Compressible and Sensitive Flexible Piezoresistive Pressure Sensor Based on MWCNTs/Ti3C2Tx MXene @ Melamine Foam for Human Gesture Monitoring and Recognition

“…These flexible devices are mainly classified into four categories, namely piezoelectricity [6,7], piezoresistivity [8,9], capacitance [10] and triboelectricity [11], according to the various transduction mechanisms. Among them, the flexible resistive-type sensors that can convert mechanical force into readable electrical resistance variation have been commonly researched due to their advantages of low cost, convenient manufacturing techniques and easy signal acquisition [12,13].…”