In photoinduced force microscopy (PIFM), amplitude modulation techniques, such as direct mode, and heterodyne amplitude modulation techniques have been used to detect the photoinduced force. These amplitude modulation techniques are affected by other forces because the resonance frequency shifts and nonconservative force damp the cantilever motion. Here, we investigate and propose the heterodyne-frequency-modulation (heterodyne-FM) technique for inhibiting the influence of the other forces and photothermal force. Heterodyne-FM PIFM enables the acquisition of PIFM images and force spectra without those artifacts.

• Received 21 August 2017
• Revised 12 December 2017

DOI:https://doi.org/10.1103/PhysRevApplied.9.024031