Direct imaging method of frequency response of capacitance in dual bias modulation electrostatic force microscopy

We have proposed and demonstrated a direct imaging method in dual bias modulation electrostatic force microscopy (DI-DEFM) to observe the frequency response of the capacitance between a conductive tip and a sample in a single scan. In DI-DEFM, dual ac biases with different frequencies (f(1), f(2)) are simultaneously applied between the tip and the sample to generate an electrostatic force; the frequencies are switched between two pairs of frequency conditions, with a switching frequency f(m). Then, the f(2) - 2f(1) - f(m) component in the electrostatic force is detected, similar to a heterodyne method, to analyze the frequency response of the capacitance. The validity of DI-DEFM is assessed through the image acquisition on a Cu(In,Ga)Se-2 sample. (C) 2020 The Japan Society of Applied Physics