  This study has successfully demonstrated a novel self-heating formaldehyde
gas sensor based on a thin film of NiO sensing layer. A new fabrication process
has been developed in which the Pt micro heater and electrodes are deposited
directly on the substrate and the NiO thin film is deposited above on the micro
heater to serve as sensing layer. Pt electrodes are formed below the sensing
layer to measure the electrical conductivity changes caused by formaldehyde
oxidation at the oxide surface. Furthermore, the upper sensing layer and
NiO/Al2O3 co-sputtering significantly increases the sensitivity of the gas
sensor, improves its detection limit capability. The microfabricated
formaldehyde gas sensor presented in this study is suitable not only for
industrial process monitoring, but also for the detection of formaldehyde
concentrations in buildings in order to safeguard human health.
