Measuring Thin Film Properties Using SAW (Surface Acoustic Wave) Devices: Diffusivity and Surface Area

摘要

Surface acoustic wave (SAW) devices have been used in two new techniques for the characterization of thin film properties. By monitoring the change in surface wave propagation velocity, the sorption of gases and vapors by a film can be recorded. In the first technique, the absorption transient for gas and vapor molecules diffusing into polymer films is observed. These transient data can be fit to a one-dimensional diffusion equation and a diffusivity extracted. In the second technique, the adsorption of nitrogen by a porous film is measured at 77 K as a function of partial pressure. The effective surface area of porous thin films can be extracted from such adsorption isotherms using standard BET analysis. 20 refs., 5 figs. (ERA citation 13:007803)