Title :
Measurement of the equivalent circuit parameters of chemical interface layers on bulk acoustic wave resonators [chemical sensor applications]
Author :
Gouws, G.J. ; Holt, R.C. ; Zhen, J.
Author_Institution :
Sch. of Chem. & Phys. Sci., Victoria Univ., Wellington, New Zealand
Abstract :
The viscoelastic properties of thin polymer layers coated on a thickness shear mode (TSM) resonator is investigated by analysis of the impedance spectra of the resonator. The response of resonators coated with polyethleneoxide (PEO) and polydimethylsiloxane (PDMS) to organic vapours is described. The PEO coated sensor shows the conventional Sauerbrey behaviour of a negative frequency shift with adsorbed mass, but the PDMS coated sensors show a strong positive frequency shift. The complex shear modulus for these layers is calculated and it is found that the PDMS is in the rubbery state. The in-diffusion of organic vapours leads to a further softening of the layer which produces the positive frequency shift.
Keywords :
acoustic resonators; adsorption; bulk acoustic wave devices; chemical sensors; equivalent circuits; polymer films; shear modulus; viscoelasticity; PEO; Sauerbrey effect; TSM resonators; adsorbed mass induced frequency shift; bulk acoustic wave resonators; chemical interface layers; complex shear modulus; equivalent circuit parameter measurement; organic vapour in-diffusion; organic vapour sensitivity; polydimethylsiloxane; polyethleneoxide coating; resonator impedance spectra; rubbery state PDMS; thickness shear mode resonators; thin polymer layer viscoelastic properties; Acoustic measurements; Acoustic waves; Chemical sensors; Elasticity; Equivalent circuits; Frequency; Impedance; Polymer films; Softening; Viscosity;
Conference_Titel :
Frequency Control Symposium and Exposition, 2004. Proceedings of the 2004 IEEE International
Print_ISBN :
0-7803-8414-8
DOI :
10.1109/FREQ.2004.1418471
