Voltage-assisted differentially grown zinc oxide nanowires based two terminal device for sensing applications

Abstract

Zinc oxide is considered an intriguing semiconductor alternative to the typically employed semiconductors. As it provides high thermal and chemical stability, a wide energy bandgap, a high electrochemical coupling coefficient, and biocompatibility, it also has a wide range of morphologies that can be used various applications. Among them, the ZnO nanowire is one of the most researched morphologies. There are different synthesis methods available for ZnO nanowire growth. In this work, a modified Chemical Bath Deposition method was implemented for ZnO nanowire formation. As the Chemical Bath Deposition is a bottom– up solution based synthesis method, it has different ions in the solution. By applying external voltage, the ion distribution can be manipulated. So a voltage-Assisted Chemical Bath Deposition method was implemented to form ZnO nanowire on a Silicon substrate. As different growth condition may effect the growth of nanowires, without changing other parameters only changing the applied voltage four devices were fabricated. Different characterisation methods such as X-Ray Diffraction (XRD) and FESEM imaging for its morphological study , Diffuse Reflectance Spectroscopy(DRS) for its optical properties, and Voltage current characteristics for electrical properties, were performed to analyse the ZnO nanowire grown on the silicon substrate and the effect of the different applied voltages. This study demonstrated the effect of voltage assisted chemical bath deposition methods on nanowire growth. To study the Chemiresistive application of the fabricated device, the device was tested against Cu (II), Cr(III),Fe(II) and Ni(II) heavy metal ions. The comparative data for four devices were analyse using current response of the devices in presence of each heavy metal ions. It was established that this device can be used as a chemiresistive sensor for Cu (II) ions.