Tabletop deep-ultraviolet transient grating for ultrafast nanoscale carrier-transport measurements in ultrawide-band-gap materials

Understanding nanoscale electron and phonon transport is critical for the development of next-generation semiconductor technologies, where deviations from macroscopic behaviors can either limit or enhance device performance. While transient gratings generated by the interference of visible lasers can directly excite microscopic, nonequilibrium charge and heat distributions in metals and traditional semiconductors, extending this noncontact approach to ultrawide-bandgap materials involves added complexities. To address these challenges, here we introduce a tabletop deep-ultraviolet (DUV; 6.3 eV) transient grating setup, and show that it supports sub-300 nm spatial and subpicosecond temporal resolution. As an initial demonstration, we excite and probe gigahertz surface acoustic waves in thin gold films. We then perform DUV transient grating measurements of nanoscale carrier transport in diamond and discuss the carrier concentration-dependent diffusion coefficient. This DUV transient grating capability provides a versatile, noncontact tool for investigating transport at length scales below the visible diffraction limit and in wide-bandgap materials, and bridges the gap between visible and facility-scale extreme-ultraviolet transient grating capabilities.