The correlation between the ability of gas adsorption and the roughness of ZnO films analyze by reflective second harmonic generation

Abstract

Surface modification of the thin film structure is one of the most feasible method to modify the surface state and their gas sensing properties Regulating and controlling the surface state of thin film are difficult but interesting things As an oxide semiconductor ZnO nanostructure is an excellent choice because the (002) plane is the lowest energy plane and easier to form nanostructure Also it’s a general compound for common photocatalysts among the metal oxides such as it is suitable to react under UV light due to its large band gap and excitation binding energy According to these properties we utilized the various stages of argon plasma bombardment process to modify the surface morphology of thin films which variation inspected by AFM and SEM The bombed surface of ZnO films not only changes the surface morphology but also vary their surface states such as the chemical bonding on the surface (or defects measured by XPS) The variation of O2 (or dissolved by ozone) adsorption and the process of desorption by UV light irradiation at varied surface morphology of ZnO thin films can be inspected by time-dependent SHG probes We observed the symmetrical pattern and amplitude of RSHG which reveals the quality of ZnO film grown on the Si (111) and the related variation of RSHG between O2 adsorption and desorption Our work provides a strong correlation between the sensitivity of gas sensor and the surface states and morphology of oxide films which is novel in the analysis of gas sensor by the viewpoint of the dipole contribution

Date of Award	2018 Aug 3
Original language	English
Supervisor	Kuang-Yao Lo (Supervisor)