Surface potential, which is directly related to the work function of materials at the surface, is an important quantity for nanoscale electrical characterization. The method of choice for measuring surface potential is the Kelvin Probe Force Microscopy (KPFM) that is based on the atomic force microscopy (AFM). However, the current amplitude modulated KPFM or frequency modulated KPFM can only provide a spatial resolution of 30-100 nm under the ambient conditions. To further improve the spatial resolution of KPFM, we invented the Pulsed Force Kelvin Probe Force Microscopy (PF-KPFM) in 2019. PF-KPFM achieves consistently < 10 nm spatial resolution on surface potential mapping on a range of samples.
The operational principle of PF-KPFM deviate from the paradigm of traditional KPFMs.
- PF-KPFM operates in the pulsed force mode (peak force tapping mode) instead of the tapping mode
- PF-KPFM uses a field effect transistor(FET) to switch ON/OFF the electrical connectivity between the AFM tip and the sample, to generate Coulomb forces
- PF-KPFM is a single pass KPFM without lift mode operation
- PF-KPFM generates signals when tip sample distance is only several nanometers
PF-KPFM is expected to enhance the capability of KPFM for surface potential mapping under regular ambient conditions.