Dissipative force modulation Kelvin probe force microscopy applying doubled frequency ac bias voltage

The authors propose a surface potential measurement technique using dissipative force modulation (DM) method with an ac bias voltage of doubled harmonic frequency (2ω) of the oscillating cantilever (2ωDM method). The effect of the stray capacitance between a cantilever and a sample on electrostatic force spectroscopy/Kelvin probe force microscopy measurement is almost completely removed in 2ωDM method, since the distance dependence of the modulated electrostatic force increases from 1∕z to 1∕z2. 2ωDM method has an advantage of high force sensitivity due to the high Q factor of the cantilever in vacuum. The authors demonstrate quantitative surface potential measurement by using dissipative tip-sample interactions.