Thin-Film Bulk-Acoustic-Resonator Gas Sensor Functionalized With a Nanocomposite Langmuir–Blodgett Layer of Carbon Nanotubes

A thin-film bulk acoustic resonator (TFBAR) based on a vibrating membrane of $\hbox{AlN/Si}_{3}\hbox{N}_{4}$ has been fabricated onto a silicon substrate and functionally characterized as gas sensor at a resonating frequency of 1.045 GHz. This novel TFBAR-based gas sensor has been functionalized by a sensing nanocomposite layer, prepared by a Langmuir–Blodgett (LB) technique, of single-walled carbon nanotubes (SWCNTs) embedded in a host matrix of organic material of cadmium arachidate. High-performance gas detection at room temperature of a SWCNT-coated TFBAR sensor has been reported. The sensing device exhibits high sensitivity (e.g., acetone: 12 kHz/ppm; ethylacetate: 17.3 kHz/ppm), fast response (within 2–3 min), slow reversibility (within 1 h), and good repeatability ($\leq \hbox{5}\%$ variation) of response toward tested organic vapors of acetone, ethylacetate, and toluene.