Non-contact atomic force microscopy characterization of micro-cantilevers and piezo electric transducers with frequencies up to the tens of MHz

We investigated the use of the non-contact atomic force microscopy (NCAFM) technique for evaluating high frequency mechanical vibrations. We demonstrated a clear resonance frequency (fres) of ∼11.8 MHz measured from a 0.25 cm2 piece Si placed on top of a driven PZT and probed by an AFM cantilever. We also showed that the probe cantilever in the NCAFM was able to follow the envelope of a Si on PZT vibration driven at 41 MHz frequency with a cyclic voltage. We showed that our method will not introduce a shift in the measured fres through comparison with the optically measured fres from a series of sample cantilevers using both mechanical excitation and the thermal noise-mechanical frequency spectra. These sample cantilevers were then measured under various conditions using the NCAFM resonance technique and the results showed a shift of <0.3% in the resonance frequency of the sample cantilevers. In addition, the sample cantilever was driven at its first harmonic frequency while the vertical displacement along its length was measured and its length dependence matched the expected first-order mode shape.