Broadband nanodielectric spectroscopy by means of amplitude modulation electrostatic force microscopy (AM-EFM)

In this work we present a new AFM based approach to measure the local dielectric response of polymer films at the nanoscale by means of Amplitude Modulation Electrostatic Force Microscopy (AM-EFM). The proposed experimental method is based on the measurement of the tip–sample force via the detection of the second harmonic component of the photosensor signal by means of a lock-in amplifier. This approach allows reaching unprecedented broad frequency range (2–3×104 Hz) without restrictions on the sample environment. The method was tested on different poly(vinyl acetate) (PVAc) films at several temperatures. Simple analytical models for describing the electric tip–sample interaction semi-quantitatively account for the dependence of the measured local dielectric response on samples with different thicknesses and at several tip–sample distances.