Fabrication and Application of Ruthenium-Doped Titanium Dioxide Films as Electrode Material for Ion-Sensitive Extended-Gate FETs

A novel ruthenium-doped titanium dioxide (TiO₂: Ru) film for pH detection is based on an ion-sensitive extended gate field effect transistor (ISEGFET) sensor. For the preparation of the TiO₂:Ru sensing film, a specific processing for metal modification of TiO₂ thin film is deposited by a co-sputtering system. After thermal annealing treatment, material analysis of the sensing layer is measured by SEM, Hall measurement system and electrical detection system. The average sensitivity of TiO₂:Ru for hydrogen ion detection is about 55.20 mV/pH (concentration range between pH1 and pH13). The effect of long-term drift for TiO₂:Ru ISEGFET-based sensor is presented. Drift rate of the sensor for pH is 0.745 mV/h for 12 h. In order to prepare the calcium ion sensor, the sensing membrane of polymer materials is based on TiO₂: Ru ISEGFET-based sensor by physical adsorption. The average sensitivity of the calcium ion sensor in the concentration ranging between 1 M and 1times10^-3 M CaCl₂ is about 29.65 mV/pCa.