Preparation and properties of lead titanate gate ion-sensitive field-effect transistors by the sol-gel method

An ion sensitive layer dominates the behavior of the ion-sensitive field-effect transistor (ISFET). In this study, the first proposed PbTiO3 (lead titanate) membrane has been prepared by the sol-gel method as a H ion sensitive layer. Relative permittivity of about 17.0 is obtained by the capacitance-voltage (C-V) measurement of an Al/PbTiO3 metal-insulator-semiconductor (MIS) structure. The fabrication parameters of the PbTiO3 membrane included a thickness of 0.5 mum and a firing temperature between 350degreesC and 400degreesC. The pH response is the quasi-Nemstian response of 56-59 mV/pH via the C-V measurement of an electrolyte-insulator-semi conductor (EIS) structure. The pH(PZC) (the point of zero charge) is about 1.8 calculated by means of the MOS theory and site-binding model. Finally, with the sample PbTiO3 gate ISFET, excellent pH responses of about 56.6 mV/pH and -24.8 muA/pH were achieved, operated at I-DS = 37 muA (constant drain-source current) and V-DS = 3 V (constant drain-source voltage), respectively.