Low-power photothermal probing of single plasmonic nanostructures with nanomechanical string resonators.
We demonstrate the direct photothermal probing and mapping of single plasmonic nanostructures via the temperature-induced detuning of nanomechanical string resonators. Single Au nanoslits and nanorods are illuminated with a partially polarized focused laser beam (λ = 633 nm) with irradiances in the range of 0.26-38 μW/μm(2). Photothermal heating maps with a resolution of ∼375 nm are obtained by scanning the laser over the nanostructures. Based on the string sensitivities, absorption efficiencies of 2.3 ± 0.3 and 1.1 ± 0.7 are extracted for a single nanoslit (53 nm × 1 μm) and nanorod (75 nm × 185 nm). Our results show that nanomechanical resonators are a unique and robust analysis tool for the low-power investigation of thermoplasmonic effects in plasmonic hot spots.
Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech , DK-2800, Kgs Lyngby, Denmark.
Silvan
S
Schmid
Kaiyu
K
Wu
Peter Emil
PE
Larsen
Tomas
T
Rindzevicius
Anja
A
Boisen