7 - Optical and optoelectronic metal oxide-based sensors; (optical sensors, principle, computational modeling, and application-based development)

Abstract

Semiconductor metal oxide (MO) has been widely explored for optical and optoelectronic devices because the MO properties are different from the conventional inorganic semiconductors like III–V and silicon groups. Several studies have found the new type of MO materials that have transparent and flexible properties with a conjugated combination of the p–n types valence band. This material has shown a unique electronic structure, a different charge transport mechanism, and excellent optoelectronic properties. Therefore, the present chapter describes the application of zinc oxide (ZnO) nanowires for hydrogen (H2) gas sensing by investigating the relationship between structural–optical properties and their effects on the sensing mechanism at room temperature. ZnO nanowires were formed at the tip of the optical fibers on the ZnO seed layer by radio frequency (RF) Magnetron Sputtering accompanied by Chemical Bath Deposition (CBD) methods for the growth of nanowires. Grown nanowires are suitable for growth in the hexagonal wurtzite crystal structure with a plane orientation of (100). Besides, the optical absorbance and bandgap of the ZnO nanowires were found to be 3.22eV and the Raman spectroscopy confirmed the active phonon modes of nanowires growth at 435cm−1 (E2 mode). The result obtained indicates the strength of H2 gas absorbed by ZnO nanowires at 1% and 2% H2 concentrations. Therefore, the growth of nanowire properties would influence the absorption of the gas sensing mechanism.