Fast, high-resolution surface potential measurements in air with heterodyne Kelvin probe force microscopy

TL;DR

This paper introduces Heterodyne Kelvin Probe Force Microscopy (H-KPFM), a method that achieves high-speed, high-resolution surface potential imaging in air, with reduced artifacts and enhanced sensitivity, enabling real-time observation of dynamic electrochemical processes.

Contribution

The paper presents H-KPFM as a novel technique that significantly improves scan speed and sensitivity while maintaining spatial resolution, and introduces a new implementation amplifying voltage signals via cantilever resonance.

Findings

H-KPFM achieves several frames per minute in air.

It maintains spatial resolution and voltage sensitivity comparable to standard methods.

It reduces topography-coupled artifacts.

Abstract

Kelvin probe force microscopy (KPFM) adapts an atomic force microscope to measure electric potential on surfaces at nanometer length scales. Here we demonstrate that Heterodyne-KPFM enables scan rates of several frames per minute in air, and concurrently maintains spatial resolution and voltage sensitivity comparable to frequency-modulation KPFM, the current spatial resolution standard. Two common classes of topography-coupled artifacts are shown to be avoidable with H-KPFM. A second implementation of H-KPFM is also introduced, in which the voltage signal is amplified by the first cantilever resonance for enhanced sensitivity. The enhanced temporal resolution of H-KPFM can enable the imaging of many dynamic processes, such as such as electrochromic switching, phase transitions, and device degredation (battery, solar, etc.), which take place over seconds to minutes and involve changes in electric potential at nanometer lengths.