2026-10-13T17:59:14Z https://api.figshare.com/v2/oai

oai:figshare.com:article/32641602 2026-10-01T16:21:55Z portal_1172 item_type_8 month_year_10_2026

Exploring nanoscale thermal variations and photo-induced surface potential enhancement in plasmonic nanostructures Serene Pauly (17281126) PUREID: 651348511 Scanning thermal microscopy plasmonics thermoplasmonics kelvin probe force microscopy Localised surface plasmon resonance (LSPR) arises when incident light drives collective oscillations of conduction electrons in metallic nanostructures, producing strong near-field enhancement and resonant optical absorption. A significant consequence of resonant excitation is conversion of absorbed optical energy into heat, producing temperature gradients confined to the nanoscale. Despite this intrinsic nanoscale, most experimental thermal characterisations remain limited to micrometre resolution owing to diffraction limits, leaving the true spatial distribution of photothermal effects largely unresolved. To resolve this limitation, a quantitative scanning-probe framework was implemented to map nanoscale temperature distributions in fabricated plasmonic arrays. Scanning thermal microscopy (SThM) was used to image ordered gold (Au) and iron (Fe) nanodome arrays under two illumination geometries: top and bottom configurations. Comparative analysis shows that top illumination affords superior optical coupling and yields larger, highly localised temperature increases (ΔT ≈ 4.7 °C at 1.6 mW), whereas bottom illumination produces smaller but resolvable rises (ΔT ≈ 0.88 °C at 1.09 mW) for identical Au nanodomes. The bottom-illumination geometry was adapted for photo-modulated Kelvin probe force microscopy (KPFM) to probe plasmo-electric effects and hot-carrier dynamics. Resonant excitation on Au/ITO substrates produced a pronounced light-induced surface-potential increase (ΔV ≈ 145 mV), consistent with plasmon-mediated charge redistribution and localized hot-electron generation. Finite-element (COMSOL) simulations of electromagnetic confinement and heat diffusion were performed to support interpretation. The combined SThM–KPFM workflow enables quantitative mapping of temperature and surface potential at sub-diffraction scales without specialised sample preparation, providing a reproducible benchmark for thermoplasmonic characterisation and plasmo-electric studies in nanophotonic devices. Thesis is embargoed until 31st December 2026. 2026-10-01T16:21:55Z Text Thesis 10.17034/32641602.v1 https://figshare.com/articles/thesis/Exploring_nanoscale_thermal_variations_and_photo-induced_surface_potential_enhancement_in_plasmonic_nanostructures/32641602 All Rights Reserved Open Access after 2026-12-31