MECHANICAL-BEHAVIOR OF FILMS ON THE QUARTZ MICROBALANCE

The influence of films on the resonance character of the quartz resona tor has been modelled from a variety of points of view. Purely mechani cal models, using the notion of the piezoelectrically stiffened modulu s, have been very successful in describing the influence of elastic fi lms. Viscoelastic behaviour required another approach and two equivale nt methods of dealing with it are possible. The ultimate objective of these is to relate the observed electrical behaviour of the resonance (obtained by impedance analysis, for example) to the physical properti es of the film. The focus has then, understandably, been on the descri ption of the electrical parameters of the resonator, as influenced by the materials properties of the film. Here, we focus instead on the me chanical behaviour of the films, using the physical model rather than the equivalent circuit approach. The amplitude of the shear displaceme nts in the quartz and in the overlayer are examined for several cases; the unloaded resonator, the resonator loaded viith elastic overlayers , the resonator loaded with a Newtonian fluid and the resonator loaded with a viscoelastic medium. The details of the mathematical analysis are given.