Abstract:
In scanning probe microscopy (SPM), piezoelectric resonators (PR) are used to control the contact of the probe with the surface, the signal of the probe pressure force on the surface being directly converted into an electrical signal. The contact of the probe with the surface should occur through the contact of only single atoms. In order to increase sensitivity, a new technique for mechanical amplification of the force signal has been developed. The PR, combined with a primitive “dynamic amplifier” (DA) and a probe, form a new resonant system in which the amplitude of the vibrations of the PR is many times different from the amplitude of the vibrations of the probe. In this system, the DA serves as the first stage of amplification, and the PR as the second, so the output signal-to-noise ratio is determined by the noise of the first stage, which can be significantly less than the noise of the PR. Such system was carried out in practice with an experimental sensitivity of 1 pN scale in the 100 Hz frequency band, which is an order of magnitude better than the fundamental theoretical limit for PR without the use of DA. A detailed theoretical calculation of such a system is given.The described principle of mechanical amplification has a universal character and will allow using the same type of commercially available PR for different SPM tasks as well as for other types of diagnostics.
Keywords:probe microscopy, force noise, resonator, bending vibrations.
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