Applying second and third resonance frequencies to surface potential measurements with Kelvin Probe Force microscopy

Abstract

Frequency separation between topography and potential scans in Kelvin probe force microscopy (KPFM) was investigated. Topographic images were scanned via the first resonance frequency of the cantilever excited mechanically. Potential images were scanned via the first, second, or third resonance frequency of the cantilever excited electrostatically. Good separation of the mechanical modulation to the cantilever in AC mode and the potential modulation to the probe tip was obtained when the second or third modulation frequency was used. Higher resonance modes led to a decreased capacitive effect between the cantilever and sample, which resulted in better lateral resolution of potential measurements, mainly owing to the tip–sample capacitive effect. The shorter time scale of amplitude change in the cantilever oscillation for the higher resonance frequencies led to well-converged potential measurements. The second and third resonance frequencies are useful for separating signals in KPFM, resulting in better lateral resolution and potential difference measurements of the sample surface.