Near-field ultrafast nanoscopy of carrier dynamics in silicon nanowires

<title>Abstract</title> Carrier distribution and dynamics in semiconductor materials often govern their physics properties that are critical to functionalities and performance in industrial applications. The continued miniaturization of electronic and photonic devices calls for new tools to probe carrier behavior in semiconductors simultaneously at the picosecond time and nanometer length scales. Here, we develop pump-probe scattering-type scanning near-field optical microscopy (s-SNOM) to characterize the carrier dynamics in semiconductor nanowires. By coupling experiments with the point-dipole model, we resolve the size-dependent photoexcited carrier lifetime in individual silicon nanowires. We further demonstrate local carrier decay time mapping in silicon nanostructures with a sub-50 nm spatial resolution. Our pump-probe s-SNOM enables the nanoimaging of ultrafast carrier kinetics, which is an important step in advancing the future design of a broad range of electronic, photonic, and optoelectronic devices.