Assessing the quality of scanning probe microscope designs

We present a method for assessing an atomic force microscope's (AFM's) ability to reject externally applied vibrations. This method is demonstrated on one commercial and two prototype AFMs. For optimally functioning AFMs, we find that the response to externally applied vibrations obeys a 1/ω² frequency dependence. This 1/ω² frequency dependence can be understood by modelling the mechanical system which connects the AFM cantilever and the sample under test as a simple harmonic oscillator. According to such a model, the resonant frequency of the mechanical system which connects the AFM cantilever and the sample under test determines an AFM's ability to reject externally applied, low-frequency vibrations.