Study on the amorphous tungsten trioxide ion-sensitive field effect transistor

In this study, the pH-sensitive properties of the amorphous tungsten trioxide (a-WO3) thin films by the RF sputtering system from a WO3 target have been investigated. The electrolyte–insulator–semiconductor (EIS) structure with a-WO3 thin film can be used to detect the sensitivity of ion and can be explained by the C–V curve in the different acidic buffer solutions (pH=1–7) using the C–V measurement. In addition, the tungsten trioxide thin films were also deposited on the double layer structure of a-WO3/SiO2 gate ion-sensitive field effect transistor (ISFET), and could obtain the shift of the linear region threshold voltage (ΔVT) of the ISFET devices in the acidic solutions. The a-WO3 materials exhibit a fairly high response, and the sensitivity is obtained at about 50 mV/pH.