Electrodeposition of High-Functional Metal Oxide on Noble Metal for MEMS Devices

MEMS gas sensors could exert a significant impact on the automotive sector since future legislation is expected to stipulate the monitoring of NOx and unburned fuel gases in vehicle exhausts. Among the materials, zinc oxide and TiO2 are the most promising and extensively used materials for monitoring of NOx gas since zinc oxide and TiO2 show the high sensitivity, good stability, and fast response. Electrochemistry is a potential method to fabricate zinc oxide and TiO2 for the applications since it is carried out at relatively low temperature and can cooperate with photolithography, which is an important process in MEMS. This study integrated zinc oxide/gold-layered structure and TiO2/NiP hybrid structure on elastic fabrics, respectively, to realize an elastic gas sensor. Electroless plating (EP) and cathodic deposition were used to metallize and deposit metal oxides on elastic fabrics. Supercritical carbon dioxide (scCO2) was further introduced into the electrochemical process to enhance the composite reliability.