Chapter 7 - Nanofabrication techniques for semiconductor chemical sensors

Abstract

Chemical sensors are defined as devices or instruments that transduce different types of chemical information such as concentration, chemical activity, and presence of metal ions or gases into a measurable and distinguishable signal. Semiconductor nanomaterials, especially one-dimensional (1D) nanomaterials like nanorods, nanoneedles, nanobelts, and nanowires, have gained tremendous attention in chemical sensing devices owing to their large surface-to-volume ratio compared with their thin film and bulk counterparts. Therefore, several 1D nanomaterials have been designed for chemical sensors for detection of O2 and H2 gases as well as various toxic and flammable materials such as NO2, CO, NH3, ethanol, etc. However, two-dimensional (2D) nanomaterials such as MX2 (M=W, Mo, and X=S, Se), graphene oxide, semiconductor metal oxides (SMO), etc. have also attracted significant attention because of their high surface-to-volume ratios, ultrahigh surface sensitivity to the environment, superior electrical/optical properties, robustness, and flexibility. These nanomaterials have been synthesized by various nanofabrication techniques such as lithography, electroplating, surface treatment by plasma, chemical vapor deposition (CVD), doping of silicon, micro-electro-mechanical systems (MEMS), and cracking. In this chapter, we discuss various fabrication techniques for different types of chemical sensors and opportunities and challenges toward practical applications of these novel materials and sensing devices.