16 - Zinc-Oxide based EGFET pH sensors

Abstract

This chapter discusses the ZnO-based extended-gate field-effect transistor (EGFET) as a pH sensor where ZnO-sensing film has been deposited by the RF sputtering technique and the fabrication approach for the development of the EGFET as a pH sensor has been elaborated. Some of the most common deposition techniques for ZnO film and its use as EGFET pH sensors have also been discussed. This chapter consists of four sections: firstly, there is a brief introduction about the zinc oxide material and their properties are discussed for various applications. In the subsequent section, the importance of the ZnO-based chemical and biological sensing and their sensing mechanisms are discussed. The third section discusses the EGFET, which consists of an extended gate connected electrically to the gate of the commercially available MOSFET; the fabrication of EGFET using standard microfabrication techniques is discussed along with its process flow. The fourth section discusses the development of nanostructured ZnO film using the RF deposition technique, where various deposition parameters including chamber pressure, deposition time, flow rate, and the RF power were also discussed; the pH-sensing experiments were also presented. The RF deposited film has been characterized by Raman spectroscopy and field emission scanning electron microscope techniques. In the last section, other relevant techniques used for the development of pure ZnO as a pH-sensing layer for EGFET are presented.