title: Polymer coating behavior of Rayleigh-SAW resonators with gold electrode structure for gas sensor applications.
abstract: Results from systematic polymer coating experiments on surface acoustic wave (SAW) resonators and coupled resonator filters (CRF) on ST-cut quartz with a corrosion-proof electrode structure entirely made of gold (Au) are presented and compared with data from similar SAW devices using aluminium (Al) electrodes. The recently developed Au devices are intended to replace their earlier Al counterparts in sensor systems operating in highly reactive chemical gas environments. Solid parylene C and soft poly[chlorotrifluoroethylene-co-vinylidene fluoride] (PCFV) polymer films are deposited under identical conditions onto the surface of Al and Au devices. The electrical performance of the Parylene C coated devices is monitored online during film deposition. The PCVF coated devices are evaluated after film deposition. The experimental data show that the Au devices can stand up to 40% thicker solid films for the same amount of loss increase than the Al devices and retain better resonance and phase characteristics. The frequency sensitivities of Au and Al devices to parylene C deposition are nearly identical. After coating with soft PCFV sensing film, the Au devices provide up to two times higher gas sensitivity when probed with cooling agent, octane, or tetrachloroethylene.
authors.affiliation: Institute of Solid State Physics, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria. iavramov@pronto.phys.bas.bg
authors.forename: Ivan D
authors.initials: ID
authors.lastname: Avramov
authors.forename: Kerstin
authors.initials: K
authors.lastname: Länge
authors.forename: Swen
authors.initials: S
authors.lastname: Rupp
authors.forename: Bastian
authors.initials: B
authors.lastname: Rapp
authors.forename: Michael
authors.initials: M
authors.lastname: Rapp
mesh_terms: D000162:Acoustics / Q000295:instrumentation*; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005740:Gases / Q000032:analysis* / Q000737:chemistry; D008839:Microelectrodes; D011108:Polymers / Q000737:chemistry*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014159:Transducers; D014732:Vibration
chemical_list: D005740:Gases; D011108:Polymers