Sputtered titanium dioxide thin film for Extended-Gate FET sensor application

This paper presents an investigation on sputtered titanium dioxide (TiO₂) thin film for application in the Extended-Gate Field Effect Transistor (EGFET) sensor application for pH detection. The TiO₂ thin film was fabricated on conductive indium-tin oxide (ITO) covered glass by using RF Sputtering method. An EGFET proof-of-concept setup was constructed using a commercial FET as the transducer and the TiO₂/ITO structure was used for the extended gate. The sensor measurement was taken using semiconductor device parametric analyzer, constant-current constant-voltage biasing interfacing circuit and data logger to obtain the sensitivity and the characteristics for output voltage with respect to time. TiO₂ thin film on ITO glass as the sensing membrane was compared with a bare ITO glass substrate for the extended gate. The TiO₂/ITO glass exhibited the sensitivity of 42.1 mV/pH and good linearity of 0.9997 in the sensing range pH4, pH7 and pH10 which was better than the bare ITO glass sensitivity of 31.3 mV/pH and the linearity of 0.9868.