FABRICATION AND CHARACTERIZATION OF PALLADIUM-DOPED ZINC OXIDE THIN FILMS AND ITS APPLICATION AS EXTENDED-GATE FIELD-EFFECT TRANSISTOR PH SENSOR

Abstract

This work presents the fabrication, characterization and performance analysis of Zinc Oxide (ZnO) and Palladium doped Zinc Oxide (Pd-ZnO) thin films based Extended-Gate Field-Effect Transistor (EGFET) pH sensor. The Pd-doped ZnO thin films with different molar concentrations (Pd = 0%, 2% and 4%) were deposited onto p-type Si<111> substrate by sol-gel method. The EGFET pH-sensor has been prepared by linking the fabricated sensing devices to the gate terminal of a commercial Metal Oxide Semiconductor Field-Effect Transistor (MOSFET CD4007UB). The fabricated sensing devices were immersed in buffer solutions with pH range of (pH 3 ‒ pH 11). The pH sensing characteristics of ZnO and Pd-ZnO/silicon EGFET devices were studied using Semiconductor Characterization System (SCS-Keithley 4200). The undoped ZnO EGFET sensor exhibits current sensitivity and linearity of 46.17 µA/pH and 97.81% with pH range of (pH 3 - pH 11) and the current sensitivity and linearity of Pd-doped ZnO (with 4% molar concentration of Pd) EGFET sensor with pH range of (pH 5 - pH 11) are 44 and 96.22%, respectively.