High-frequency mechanical spectroscopy with an atomic force microscope

In this article we further develop local mechanical spectroscopy and extend the frequency range over which it can be used. Using a heterodyne method t o measure the deflection of the cantilever enables one to measure the probe vibration at any frequency. Since the detection sensitivity of force gradi ents follows a f(2) dependence, extending the frequency range from 1 to mor e than 5 MHz increases the sensitivity by over an order of magnitude. This setup is combined with a realistic model of the cantilever taking into acco unt the geometry of the cantilever. The model is presented and discussed, a nd compared with experimental behavior measured on WC-Co and NiTi-epoxy sam ples. Experimental moduli of 730+/-50 and 260+/-40 GPa are obtained for WC and Co, respectively. (C) 2001 American Institute of Physics.