Integration of ZnO nanoflakes with MEMS platform and its application as gas sensor

MEMS based gas sensors offer superior performance compared to conventional ceramic gas sensors owing to their low power consumption, high sensitivity, faster response and compatibility to CMOS circuits. The design of microheater on the thin membrane of the MEMS structure is crucial to achieve the required temperature. In this paper a meander shaped microheater has been designed using Intellisuite v8.2 and fabricated using a nickel alloy (DilverP1) on micromachined silicon platform (2mm×2mm). A low temperature chemical deposition technique (using Sodium Zincate bath) has been adopted to deposit the sensing layer on top of the microheater. Structural morphology of ZnO was studied by FESEM. The hexagonal nanoflake like structures having average size of 50-70nm were formed. Resistive planar contacts (Au-Au) have been taken and the device was then tested for its hydrogen sensing property at different bias voltages (0-3V) and with different operating temperatures (30-210 °C) taking N₂ as a carrier gas. The optimum operating temperature was found ~ 150°C with a high response magnitude of ~80.7% and appreciably fast response time ~29.6s at a H₂ concentration of 20000ppm. At lower concentration level (100ppm) the sensor performance was also found to be promising with RM of ~36.8% and response time of 40.8s.