High-Performance Strain Sensors Based on Vertically Aligned Piezoelectric Zinc Oxide Nanowire Array/Graphene Nanohybrids

Abstract

A nanohybrid piezoelectric strain sensor was fabricated by growing vertically aligned (0001)oriented crystalline zinc oxide nanowires directly on graphene (ZnO-VANWs/Gr) using a facile seedless hydrothermal process. Under mechanical strains, the induced piezoelectric effect on the ZnO-VANWs transduces to a piezoelectric gating effect at the ZnO-VANWs/Gr interface, resulting in a modulation of the conductivity of the Gr channel through electrostatic doping. The vertical alignment of the (0001)-oriented ZnO-VANWs on Gr is ideal to achieving high strain sensitivity, and a low-defect ZnO-VANWs/Gr interface obtained in the seedless hydrothermal process is key to realizing high sensitivity and fast response. Indeed, a high sensitivity up to 3.15 × 10 −2 kPa −1 was obtained on the ZnO-VANWs/Gr strain sensors at lower pressures of 1.1 × 10 −6 −11 Torr, together with a fast response time of ∼0.10 s. In particular, these results represent enhancement factors of ∼7 and 8, respectively, as compared to strain sensors of a similar structure, except having a polycrystalline ZnO seed layer on Gr for the growth of ZnO-VANWs. Therefore, our result illustrates the critical importance of the low-defect interface of the ZnO-VANWs with Gr formed in the seedless ZnO-VANW growth for realizing an optimal electrostatic gating of Gr. In addition, the ZnO-VANWs/Gr nanohybrids can be readily scaled up using the seedless hydrothermal process for commercial applications in optoelectronics and sensors.

Optoelectronic properties and strain regulation of the 2D WS2/ZnO van der Waals heterostructure

“…However, peculiar electronic behavior subjected to mechanical strain has been observed in ZnO and some TMDs recently. [21][22][23] Thus, a biaxial strain is applied to control the band edge position, regulate the band structure, and make it a good reducing agent in water splitting. At present, 2D MX 2 -based vdWs heterostructures are mainly achieved by transfer techniques.…”

Controlled Fabrication of Quality ZnO NWs/CNTs and ZnO NWs/Gr Heterostructures via Direct Two-Step CVD Method

“…Preparing interfaces between two or more nanomaterials provides opportunities to harness properties inherent to each material and synergistically combine them to create a broader range of applications. Hybrid structures assembled from CNTs and ZnO NWs [ 20 , 29 ] and graphene and ZnO NWs [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ] have been examined and shown promising results of the enhancement of their native properties when two materials are integrally combined. In a recent study, researchers have reported high-performance supercapacitor electrodes (~192 F/g capacitance) manufactured using hybrid structures of ZnO NWs on aligned MWCNTs [ 38 ].…”

“…Previous studies have reported ZnO NWs grown on graphene via a solution-based hydrothermal method and have shown that graphene can be beneficial to the growth of ZnO NWs and can enhance their field electron emission [ 30 ]. At the same time, hybrid systems made of Gr/ZnO or graphene oxide/ZnO structures have also been shown to operate as hydrogen sensors [ 31 ], strain sensors [ 32 ], and for the photoinactivation of bacteria [ 33 ] effectively. Hybrid materials in these studies were formed through hydrothermal growth or proximity placement methods; we found that the piezoelectric, photoactive, and antibacterial properties of 1D ZnO NWs combine well with the conductive, transparent 2D support structure of the graphene sheet.…”

“…Hybrid materials in these studies were formed through hydrothermal growth or proximity placement methods; we found that the piezoelectric, photoactive, and antibacterial properties of 1D ZnO NWs combine well with the conductive, transparent 2D support structure of the graphene sheet. This makes hybrid ZnO NWs/Gr structures a promising nanomaterial for use in sensors [ 31 , 32 ], photovoltaic cells [ 34 ], and energy storage [ 35 ].…”

Finite Element Modelling of Bandgap Engineered Graphene FET with the Application in Sensing Methanethiol Biomarker

“…The sensor works based on the change in the hall resistance of the graphene layer as the local carrier concentration varies due to the adsorption of NO 2 molecules on the surface. Thereafter, researchers work extensively on graphene and its derivatives for sensory activities based on piezoelectric effects [ 37 , 38 , 39 , 40 ], optical effects [ 41 , 42 , 43 ], surface phenomenon [ 44 , 45 , 46 ], and others. The contemporary graphene sensor technology is mostly based on a GFET [ 20 , 23 , 47 ].…”