Development of CNT-ISFET based pH sensing system using atomic force microscopy

Abstract

In recent years, there has been an increasing interest in the monitoring and controlling of pH. It has become an important aspect of many industrial wastewater treatment processes as well as a drinking water quality issue. At the same time, the demand for smaller electronic devices used for various industrial and commercial applications has greatly increased. Nanomaterials such as Carbon Nanotubes (CNTs) are well known for their excellent electrical, mechanical, and thermal properties. Therefore, CNTs are good candidates for the manufacturing of small devices. In this paper, a novel concept combining CNT and Ion Sensitive Field Effect Transistor (ISFET) is proposed for pH-sensing application. Atomic Force Microscope (AFM) based manipulation and electrical property measurements in nano level are involved. Nanochannels are created by AFM-based nanoscratching, and the electrical properties of both multi-walled and single-walled CNTs are tested using Current Sensing AFM. FETs are fabricated to test the possibility of the CNTs’ alignment between the source and the drain electrode using Dielectrophoresis (DEP). The experimental results reveal that CNT is a promising material for improving the performance and lowering the cost of existing pH chemical sensors.