High speed mapping of surface charge dynamics via Spiral Scanning Kelvin Probe Force Microscopy

Abstract Understanding local dynamic charge processes is essential for developing advanced materials and devices, from batteries and microelectronics to medicine and biology. Continued progress relies on the ability to map electronic and ionic transport phenomena across different time and length scales, encompassing the intrinsic heterogeneities of the material itself (e.g., grain boundaries, domain walls, etc.). To address this challenge, we introduce high-speed Spiral-Scanning Kelvin Probe Force Microscopy (SS-KPFM), which combines sparse spiral scanning and image reconstruction via Gaussian process optimization. SS-KPFM enables functional sub-second imaging rates (≈ 3 fps), which represents a significant improvement over current state-of-the-art and several orders of magnitude over traditional KPFM methods. We apply it to study the spatiotemporal charge dynamics at a LaAlO3/SrTiO3 planar device and charge injection and diffusion dynamics in polycrystalline TiO2 thin films, providing full 2D Contact Potential Difference (CPD) maps of the surface charge dynamics in a fast and automated fashion.