Kelvin Probe Force Microscopy (KFM) in an oscillating mode of atomic force microscopy that maps the surface potential for a sample in addition to topography. High Definition KFM (HD KFM) is an optimized single-pass mode that yields data with high sensitivity and higher spatial resolution compared to a dual-pass lift KFM mode.
HD KFM image of graphene using single-pass technique with the Nano-Observer AFM
The Nano-Observer AFM can perform dual or single-pass KFM measurements. Applications that benefit from KFM include materials science, semiconductors, polymers, and biological science.
Kelvin Probe Force Microscopy uses an electrically-conductive probe to map the surface potential. The electrostatic interaction between the tip and sample is minimized using a bias voltage. For metallic samples, the voltage is the local workfunction difference between the tip and sample. For insulators, the surface charge is measured.
Whether for semiconductors, biological samples or polymers, the surface potential distribution correlates local structure and composition to an applied function. Examples of KFM applications include measuring local dopant concentrations, determining photo-induced charge separation, mapping local material contrast at grain boundaries and revealing surface heterogeneities in cellular structures.
Dual-pass versus Single-pass KFM
In the standard KFM mode, two passes are required. In the second pass, the tip is lifted from the surface, decreasing resolution and sensitivity. With HD KFM, data is acquired in a single pass for images with higher resolution and sensitivity.
Schematic of lift mode vs. single pass used for HD KFM mode