Effect of Mg2+-dopant on the characteristics of lead titanate sensing membrane for ion-sensitive field-effect transistors

A sol–gel-derived lead titanate (PT) membrane was successfully applied as a novel pH-sensing layer. However, many negatively charged defects exist within the amorphous PT membrane. The ion-sensitive field-effect transistor with the PT sensing membrane is improved using acceptor ions such as Mg2+ to substitute in the Ti4+ sites. This substitution results in reduced localized states and improving a slower response. Therefore, a sol–gel-derived Mg-modified lead titanate is adopted as a new pH-sensing layer. The result produces a pH response of 58–59 mV/pH, with drift of as low as 0.4 mV/h, hysteresis of 1–3 mV and a reduction rate of −0.2 μV/pH-day. The results show that the pH-sensing characteristics can be improved with suitable impurity doping.