Preparation and Properties of Lead Titanate Gate Ion-Sensitive Field-Effect Transistors by the Sol–Gel Method

Abstract

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 µm and a firing temperature between 350°C and 400°C. The pH response is the quasi-Nernstian response of 56–59 mV/pH via the C–V measurement of an electrolyte-insulator-semiconductor (EIS) structure. The pHPZC (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 µA/pH were achieved, operated at IDS = 37 µA (constant drain-source current) and VDS = 3 V (constant drain-source voltage), respectively.