Single-Harmonic Response Open-Loop Kelvin-Probe Force Microscopy

The measurement of electrical surface charges and their associated potentials at the nanoscale plays a crucial role in understanding important molecular processes, such as corrosion or biological tissue interactions. Measurement of these potential distributions, especially in aqueous environments, is not always possible with standard atomic force microscopy (AFM)-based techniques. The herein proposed single-harmonic response open-loop Kelvin-probe force microscopy (SH-KPFM) mode circumvents issues of common methods and enables such investigations in water via a suitable choice of the electrical excitation signal. The mode is validated using parameter sweeps on calibration samples and compared to conventional KPFM in air. Furthermore, SH-KPFM is applied to investigate the potential distribution and time-dependent depolarization of a charged PMMA surface immersed in deionized water, demonstrating its ability to analyze complex electrostatic interactions on the nanoscale.