Frequency dependent Kelvin probe force microscopy on silicon surfaces

At the example of cross-sectionally prepared p-p+-silicon epilayers on silicon, this work studies the frequency dependence of the contact potential difference detected in Kelvin probe force microscopy. The experimental setup employs a single-path off-resonance technique, which has been modified in order to enlarge the frequency range to 1–330kHz. It works with stiff cantilevers at approximately 340kHz resonance frequency and electrical signal amplitudes below 20pm. The setup utilizes multiple-channel digital lock-in amplification and a dedicated background correction, whose principle and experimental realization is described in detail and whose effect on the contact potential difference results is studied exemplarily.