# Synchronized modulation Kelvin probe force microscopy for surface photovoltage studies in optoelectronic systems

## TL;DR

A new microscopy technique called SM-KPFM is introduced to study surface photovoltage in optoelectronic materials with higher accuracy.

## Contribution

SM-KPFM synchronizes external stimulus modulation with scanning to reduce drift and thermal artifacts in surface photovoltage measurements.

## Key findings

- SM-KPFM enables drift-free surface photovoltage mapping in optoelectronic systems.
- The technique was successfully demonstrated on a silicon photodiode and a molybdenum disulfide bilayer on gold.

## Abstract

We introduce synchronized modulation Kelvin probe force microscopy (SM-KPFM), an in-operando technique that synchronizes external stimulus modulation, such as illumination or bias, with the scanning direction of the atomic force microscope to minimize artifacts from drift, thermal effects, and probe degradation. In synchronized illumination KPFM, the sample is illuminated during retrace and dark during trace, enabling real-time comparison of surface potentials within a single raster frame. At the example of a silicon photodiode and a molybdenum disulfide bilayer on gold, these superior properties are demonstrated, yielding drift-free, accurate surface photovoltage maps and clearer insights into photovoltaic effects.

The online version contains supplementary material available at 10.1557/s43579-025-00899-3.