Capacitive Crosstalk in AM-Mode KPFM

Abstract

In Kelvin probe force microscopes based on electrostatic tip excitation, a nonnegligible capacitive crosstalk occurs between the electrostatic probe excitation signal and the probe deflection output signal. In atomic force microscopy setups where a self-oscillation force feedback loop is used, the parasitic coupling may also superpose onto the piezomechanical tip excitation signal which provides the oscillation for topography imaging. As a result, the crosstalk cannot be described as a constant coupling to the deflection signal output, but rather has the effect of a spurious excitation signal, which makes it more difficult to quantify and compensate the effect. In this chapter, the phenomenon of capacitive crosstalk is studied in two frequently used AM-KPFM setups, operating in ultrahigh vacuum and in air. Different methods of reducing or eliminating the effect on the measured surface potential are described and compared.