This work explores how phonon-assisted processes and nanoscale design converge to boost
optoelectronic performance, using electron-beam lithography (EBL) to fabricate two types of
advanced metasurfaces.
In the first study, BiVO 4 metasurfaces are tailored to enhance infrared absorption near
980 nm. Charge transport in BiVO 4 is typically hindered by defect trapping and polaron
formation. By nanostructuring the material and introducing targeted IR illumination, specific
phonon modes are excited, enabling trapped electrons to return to the conduction band. Pump-
push photocurrent experiments suggest improved charge separation and extraction under
combined visible and IR light-revealing a phonon-assisted mechanism that could enhance
carrier mobility in metal oxide photoelectrodes.
The second study investigates alternating arrays of gold and silicon nanostructures designed
to generate and guide surface acoustic waves (SAWs). Ultrafast laser pulses induce rapid
thermal expansion, launching coherent acoustic phonons. Pump-probe measurements and
simulations are used to study the interaction between phonon modes generated by both
plasmonic (Au) and dielectric (Si) elements. The interplay and mixing of these modes are
actively explored to understand how array geometry influences wave interference and
focusing, with the goal of enabling tunable acoustic energy landscapes at the nanoscale.
Together, these studies demonstrate the capabilities enabled by nanometer-precision
metasurface design to harness phonon-assisted effects for improved light manipulation and
charge transport. The results point toward new design strategies for advancing solar energy
and optoelectronic devices, with ongoing research focused on refining phonon control at the
nanoscale.