Surface acoustic wave (SAW) technology has been widely developed for ultraviolet (UV) detection due to its advantages of miniaturization, portability, potential to be integrated with microelectronics, and passive/wireless capabilities. To enhance UV sensitivities, nanowires (NWs) such as ZnO are often applied to enhance SAW based UV detection, due to their highly porous and interconnected 3D network structures and good UV sensitivity. However, ZnO NWs are normally hydrophilic, and thus changes of environmental parameters such as humidity will significantly influence the detection precision and sensitivity of the SAW based UV sensors. To solve this issue, in this work, we proposed a new strategy using ZnO NWs wrapped with hydrophobic silica nanoparticles as the effective sensing layer. Analysis of distribution and chemical bonds of these hydrophobic silica nanoparticles showed that numerous C-F bonds (which are hydrophobic) were found on the surface of sensitive layer, which effectively block the adsorption of water molecules onto the ZnO NWs. This new sensing layer design endows the ZnO NWs based UV sensor with a minimized humidity interference within the relatively humidity range between 10% and 70%. The sensor showed a UV sensitivity of 9.53 ppm (mW/cm2)-1, with a high linearity (R2 value is 0.99904), small hysteresis (less than 1.65%) and a good repeatability. This work solves the long-term dilemma for ZnO NWs based sensors which are often sensitive to humidity changes.
|Journal||Microsystems and Nanoengineering|
|Publication status||Accepted/In press - 7 Aug 2022|