The effects of ultraviolet radiation, humidity and reducing gases on the temperature coefficient of resonant frequency of ZnO based film bulk acoustic-wave resonator

This paper described the influence of ultraviolet (UV) radiation, relative humidity (RH) and reducing gases on the temperature coefficient of resonant frequency (TCF) of ZnO based Film Bulk Acoustic-wave Resonator (FBAR). Under UV illumination, the TCF of the FBAR increased. This was attributed to the adsorption of oxygen due to the electrons generated by UV absorption. Water molecules can replace adsorbed oxygen on the ZnO surface. However at high temperature, less water can be sustained by the ZnO film due to its energetically unstable nature. In this way, the TCF in high RH became smaller. When reducing gases, such as acetone, were exposed to FBAR, a smaller TCF was observed.