Performance optimization of surface acoustic wave chemical sensors

摘要

Acoustic wave devices coated with a thin layer of chemoselectivenmaterial provide highly sensitive chemical sensors for the detection andnmonitoring of vapors and gases. In this work, a variety of coatingnmaterials and coating deposition techniques have been evaluated onnsurface acoustic wave (SAW) devices. A novel thin film depositionntechnique, matrix assisted pulsed laser evaporation (MAPLE), is utilizednto coat high quality polymer films on SAW devices, and conventionalnpulsed laser deposition is used to deposit a passivation layer ofndiamond-like-carbon on a SAW device surface to prevent water adsorption.nIn addition, chemoselective coatings are formed by covalent attachmentnof functionalized species to the silica surface of SAW devices. Thenself-assembled monolayer or near monolayer structures are designed tonpopulate the SAW device surface with the desirable hexafluoroisopropanolnmoeity. The rapid kinetic signals achievable with the various coated SAWnsensors during vapor tests are examined as a function of the coatingnmaterial and the quality of the thin films. In parallel to the thin filmndeposition, growth, and vapor testing, the electrical characteristics ofnthe SAW sensor have been characterized. The quality factor and residualnphase noise of polymer coated SAW devices are examined, and a predictionnof the theoretical limit of the phase noise performance of the loopnoscillator is made