ABSTRACT
This chapter provides a comprehensive discussion on the necessity and importance of developing gas sensors on a low-cost complementary metal oxide semiconductor (CMOS) platform technology. The main focus is on the challenges of integrating microhotplate-based gas sensors into a standard CMOS process. It describes the two types of microhotplate-based gas sensors: resistive and calorimetric. Although metal oxides are popular as the sensing layer, a well-known problem with these sensing materials is their lack of selectivity. Apart from metal oxides, other new-generation materials that have recently been investigated as sensing materials are carbon nanotubes and graphene. The operational principle of graphene as a gas-sensing layer is believed to be similar to that of metal oxides where conductivity changes due to adsorbed gas molecules at the graphene surface (which act as donors or acceptors). However, graphene has extra edge over metal oxides due to its unique properties.
