In this investigation, we utilize co-sputtering system to prepare ruthenium-doped titanium dioxide (TiO2:Ru) sensing film. Co-sputtering system consists of radio frequency (R.F.) and direct current (D.C.) power generators. TiO2:Ru sensing film is deposited on p-type silicon substrate. TiO2:Ru sensing film is based on gate of extended gate field effect transistor (EGFET). Sensitivity and linearity of TiO2:Ru sensing device were measured between pH1 and pH13 by current–voltage (I–V) measurement system (Keithley 236), which are 55.20 mV/pH and 0.999, respectively. In order to understand material characteristics of TiO2:Ru sensing film, we used field emission scanning electron microscopy (FE-SEM) to observe surface morphology of TiO2:Ru sensing film that is nanoscale cubic structure. The cubic size is nanoscale between 37 nm and 43 nm. Furthermore, we also used atomic force microscopy (AFM) and X-ray diffraction (XRD) to observe surface roughness and crystalline phase, respectively. According to the measured results, TiO2:Ru sensing film has superior sensing characteristics, thus it can be applied to other sensors such as ion sensors and biosensors. In this study, the calcium ion selective membrane is based on surface of TiO2:Ru sensing film. The calcium ion sensor is utilized to measure ion concentrations, which was immersed into sample liquids of CaCl2 between 1 M and 1 × 10−3 M. Sensitivity and linearity of calcium ion sensor are 29.65 mV/pH and 0.999, respectively.
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