Non-contact measurements of nanoscale phonon and electron transport with ultrafast, coherent short-wavelength light

The miniaturization of technology over the past few decades has generated enormous demand for experimental techniques capable of resolving material dynamics at ever shorter length and time scales. Ultrafast, coherent ultraviolet light provides a window into microscopic dynamics, combining femtosecond pulse durations, short wavelengths and tunable sensitivity to electronic and thermal processes. This thesis furthers the development of novel ultraviolet metrology tools and their application to nanoscale phonon and electron transport, where confinement and nonequilibrium conditions give rise to surprising new phenomena. Using extreme ultraviolet scatterometry, we extract the thermal and elastic properties of a 3D phononic crystal metalattice, nanostructured on ≪100 nm length scales, and combine the results with previous experiments and atomistic simulations to propose a new effective description of highly-confined heat flow in nanostructured semiconductors. An interlude discusses the challenges associated with contact- and fabrication-based approaches to studying transport phenomena in the context of the wider array of materials appearing in modern nanotechnology. The final chapter introduces a new non-contact deep-ultraviolet (6.3 eV) transient grating experiment, capable of investigating nanoscale phonon and electron transport in ultrawidebandgap
materials at femtosecond timescales. This new technique bridges previous laboratory and facility-scale capabilities and provides new opportunities for studying emergent nanoscale transport phenomena of relevance to next-generation energy and semiconductor technologies.