Design, fabrication and characterization of a low-power gas sensor with high sensitivity to CO gas

Co-planar type micro gas sensors of high sensitivity and fast response were prepared by using a micro electro mechanical systems (MEMS) process and a sol-gel method. The MEMS devices were designed and fabricated for low power consumption and high efficiency by adjusting the heater pattern and line width of the micro-heater. A finite element method (FEM) analysis was conducted for predicting the thermal efficiency and the temperature distribution, and the maximum value of the thermal efficiency was confirmed at a 60-μm width of the cap type mono line micro heater. The particle sizes of the SnO₂, the sensing material prepared by using a sol-gel process, was about 40 nm ∼50 nm, and the maximum gas sensitivity of the fabricated sensor was Rs = 0.312 to 50 ppm CO gas at a 1.8-V heater voltage. The high sensitivity of the fabricated sensor for CO gas resulted from a reduction of the potential barrier, which was due to the overlapping of the depletion layer on the surfaces of the nano-sized SnO₂ particles.