Microfabrication and chemoresistive characteristics of SBA-15-templated mesoporous carbon gas sensors with CMOS compatibility

Abstract

We describe a new class of silicon-based gas sensors that employ gas-sensitive films made of hexagonally ordered mesoporous carbon nanopowders. The mesoporous carbon powders (MCPs) are replicated by the SBA-15 silica template and immobilized between interdigitated Cr electrodes on a 300 μm × 300 μm active area using an alternating current dielectrophoresis (DEP) process at room temperature. The silicon sensor platform comprises Cr microheaters embedded in a dielectric thin membrane formed by conventional back-etching techniques with microelectromechanical systems (MEMS) manufacturability and complementary metal oxide semiconductor (CMOS) compatibility. It is observed that MCPs can be satisfactorily aligned along electric fields and accumulated to the electrode region. Comprehensive investigations are carried out to evaluate the gas-sensitive characteristics of MCP nanoparticles to gases such as O 2 and NH 3 for the first time. Experimental results disclose that the amorphous carbon powders are chemoresistively sensitive to oxidising and reducing gas species, and demonstrate distinct resistance change with gas concentrations in ppm-level. Fast response times estimated as ∼100 s for O 2 and ∼90 s for NH 3 and reproducible response behaviour are observed. The measured characteristics reported in this paper make MCPs a competitive alternative to carbon nanotubes (CNTs) because of their superior porosity, high specific surface area and cost-effective immobilization process.