Low Cost Environmental Sensors Using Zinc Oxide Nanowires and Nanostructures

Abstract

ABSTRACTZinc oxide (ZnO) nanowires (NW) are grown on both silicon and sapphire substrates using conventional chemical vapor deposition (CVD) system. As-grown nanostructures are characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) as well as energy dispersive spectroscopy (EDS) and the results confirm high-quality c-axis growth of single-crystalline zinc oxide nanowires. Nanowire are dispersed in solvent and then placed between micro-patterned gold electrodes fabricated on silicon wafers using low cost and scalable dielectrophoresis (DEP) process for fabrication of oxygen and humidity sensors. These sensors are characterized in a vacuum chamber connected to a semiconductor analyzer. Current-voltage characteristics of each device are systematically investigated under different hydrostatic pressure of various gaseous environments such as nitrogen, argon, dry and humid air. It is observed that the electrical conductivity of the nanowires is significantly dependent on the number of oxygen and water molecules adsorbed to the surface of the metal oxide nanowire. These results are critical for development of low cost metal oxide sensors for high performance ubiquitous environmental sensors of oxygen and humidity.