Oak Ridge National Laboratory,
Keywords: atomic force microscopy, kelvin probe force microscopy, gaussian process, image reconstruction, time resolved
Summary:Knowledge about charge dynamics is critical for a host of next generation materials and devices from batteries, electronic and optoelectronic devices to medicine and biology. This brings forward the challenge of nanoscale mapping of fast dynamic processes in materials to be crucial for continued progress in nanotechnology. Here we develop a fast-scanning KPFM based on sparse scanning (through nonrectangular scan paths) and image reconstruction (via gaussian processing). We first demonstrate that the method allows to recover the surface potential difference in standard calibration sample, by comparing different modes of KPFM operation (open loop vs closed loop). Using a spiral scan path and heterodyne KPFM detection, we show its capabilities by imaging the surface potential of 2D WS2 flakes and a nanopatterned polarized PZT thin film. Throughout, we discuss the limitations of various KPFM implementations and scan paths from the spatial and temporal resolution point of view. Finally, we demonstrate its applicability to map surface charge dynamics in LaAlO3/SrTiO3 heterointerface by triggering polarization and relaxation processes via electric field application through planar electrodes. We show that we can recover the full 2D surface potential maps at ≈3-4 frames per second in a non-spectroscopic manner, allowing to generate real space maps of characteristic local time constants in an automated and fast manner.