Open loop Kelvin probe force microscopy with single and multi-frequency excitation.

Area of Science:

• Surface Science
• Nanotechnology
• Materials Science

Background:

• Conventional Kelvin probe force microscopy (KPFM) uses closed-loop (CL) bias feedback to measure surface potential (SP).
• CL-KPFM is susceptible to systematic errors and topographical crosstalk due to non-electrostatic signal contributions.
• Accurate SP measurements are crucial for understanding material properties and device performance.

Purpose of the Study:

• To investigate open-loop (OL)-KPFM modes for quantitative and crosstalk-free SP measurements.
• To contrast OL-KPFM performance with conventional CL-KPFM for graphene on Cu foil.
• To identify and quantify errors in CL-KPFM measurements.

Main Methods:

• Implementation and testing of OL-KPFM in single and multi-frequency excitation regimes.
• Direct comparison of SP measurements obtained via OL-KPFM and CL-KPFM.
• Analysis of graphene structures (single/multilayer) and Al2O3-coated surfaces.

Main Results:

• OL-KPFM successfully yielded quantitative SP measurements.
• The SP difference between single and multilayer graphene was 63 ± 11 mV using OL-KPFM.
• An offset of 55 mV was observed between absolute SP values from OL-KPFM and CL-KPFM, attributed to non-electrostatic contributions in CL-KPFM.

Conclusions:

• OL-KPFM provides a more accurate and reliable method for determining surface potential compared to CL-KPFM.
• Non-electrostatic contributions significantly impact CL-KPFM accuracy, leading to systematic errors.
• OL-KPFM is a valuable technique for precise surface potential analysis in nanomaterials.