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The heterodyne technique is used to detect short-range forces. Using the heterodyne technique, we demonstrate photoinduced force microscopy (PiFM) imaging and z-spectroscopy without the artifact of photothermal vibration. The rejection ratio was at least 99.975% under a high-scattering condition. In addition, the heterodyne technique employs the optimal amplitude at the first resonance frequency of the cantilever to detect the photoinduced force sensitively. According to our calculation, the optimal ratio of the amplitude to the distance between the dipole of the tip and that of the sample is 0.4448. The heterodyne technique can be employed to perform PiFM without the artifact by using the optimal amplitude.

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Complex interplay between topography and dissipation signals in Non-Contact Atomic Force Microscopy (NC-AFM) is studied by a combination of state-of-the-art theory and experiment applied to the Si(001) surface prone to instabilities. Considering a wide range of tip-sample separations down to the near-contact regime and several tip models, both stiff and more flexible, a sophisticated architecture of hysteresis loops in the simulated tip force-distance curves is revealed. At small tip-surface distances the dissipation was found to be comprised of two related contributions due to both the surface and tip. These are accompanied by the corresponding surface and tip distortion approach-retraction dynamics. Qualitative conclusions drawn from the theoretical simulations such as large dissipation signals (>1.0 eV) and a step-like dissipation dependent on the tip-surface distance are broadly supported by the experimental observations. In view of the obtained results we also discuss the reproducibility of NC-AFM imaging.