ZnO nanowires grown on SOI CMOS substrate for ethanol sensing

2010-04-29
Santra, S.
Guha, P. K.
Ali, S. Z.
Hiralal, P.
Ünalan, Hüsnü Emrah
Covington, J. A.
Amaratunga, G. A. J.
Milne, W. I.
Gardner, J. W.
Udrea, F.
This paper reports on the integration of zinc oxide nanowires (ZnO NWs) with a silicon on insulator (SOI) CMOS (complementary metal oxide semiconductor) micro-hotplate for use as an alcohol sensor. The micro-hotplates consist of a silicon resistive micro-heater embedded within a membrane (composed of silicon oxide and silicon nitride, supported on a silicon substrate) and gold bump bonded aluminum electrodes that are used to make an ohmic contact with the sensing material. ZnO NWs were grown by a simple, low-cost hydrothermal method and characterised using SEM, XRD and photoluminiscence methods. The chemical sensitivity of the on-chip NWs to ethanol vapour (at different humidity levels) was characterised at two different temperatures namely, 300 degrees C and 400 degrees C (power consumption was 24 mW and 33 mW, respectively), and the sensitivity was found to be 0.1%/ppm (response 4.7 at 4363 ppm). These results show that ZnO NWs are a promising material for use as a CMOS ethanol gas sensor that offers low cost, low power consumption and integrated circuitry.