DC-Bias-free Surface Potential Measurements by Heterodyne AC Kelvin Probe Force Microscopy

This paper presents the development of a novel Atomic Force Microscopy mode, enabling dc-bias-free surface potential measurements with high spatial resolution. The influence of the cantilever cone, cantilever beam and lift height in dc-biasfree Kelvin Probe Force Microscopy (AC-KPFM) is reduced due to the proposed heterodyne detection principle, which is sensitive to the electrostatic force gradient. The accuracy of the potential measurement as compared to amplitude modulated KPFM modes is improved, while keeping the advantages of closed-loop and dc-bias-free operation. Measurements on a gold-aluminum test-sample show an increase in spatial resolution of 37% and lift height independent, quantitative surface potential measurements.