THE INFLUENCE OF A VISCOUS-FLUID ON THE VIBRATION DYNAMICS OF SCANNING NEAR-FIELD OPTICAL MICROSCOPY FIBER PROBES AND ATOMIC-FORCE MICROSCOPY CANTILEVERS

The influence of a viscous fluid on the dynamic behavior of a vibratin g scanning near-field optical microscopy fiber tip is investigated bot h theoretically and experimentally. A continuum mechanical description of a cylindric cantilever is used to calculate the resonance frequenc ies and the widths of the resonance bands. The linearized Naviers-Stok es equations are analytically solved and describe the interaction of t he beam with the viscous fluid. The contribution of the liquid to the shift and the broadening of the resonance lines is summarized by two c onstants that can be derived from a master function and the kinetic Re ynolds number. The theoretical values are compared with experimental d ata collected from an optical fiber which is used as a probe in a scan ning near-field microscope. Agreement, with a relative error of less t han 1%, is achieved. The theory is further developed for the applicati on to atomic force microscopy cantilevers with a rectangular cross sec tion. Experimental data taken from literature are in good agreement wi th the theory. (C) 1998 American Institute of Physics. [S0021-8979(98) 07916-X]