Plasmonic heating in Au nanowires at low Temperatures: The role of thermal boundary resistance

TL;DR

This study investigates laser-induced heating of gold nanowires at cryogenic temperatures, highlighting the critical role of thermal boundary resistance in heat dissipation and its impact on low-temperature spectroscopic applications.

Contribution

It provides a detailed analysis of plasmonic heating at low temperatures and demonstrates how substrate choice and thermal boundary resistance influence local temperature increases.

Findings

Local temperature increase can reach 100 K at 5 K substrate temperature.

Switching to sapphire or quartz reduces temperature rise by about three times.

Thermal boundary resistance largely governs heat dissipation below 50 K.

Abstract

Inelastic electron tunneling and surface-enhanced optical spectroscopies at the molecular scale require cryogenic local temperatures even under illumination - conditions that are challenging to achieve with plasmonically resonant metallic nanostructures. We report a detailed study of the laser heating of plasmonically active nanowires at substrate temperatures from 5 to 60 K. The increase of the local temperature of the nanowire is quantified by a bolometric approach and could be as large as 100 K for a substrate temperature of 5 K and typical values of laser intensity. We also demonstrate that a $\sim 3\times$ reduction of the local temperature increase is possible by switching to a sapphire or quartz substrate. Finite element modeling of the heat dissipation reveals that the local temperature increase of the nanowire at temperatures below $\sim$50 K is determined largely by the thermal boundary resistance of the metal-substrate interface. The model reproduces the striking experimental trend that in this regime the temperature of the nanowire varies nonlinearly with the incident optical power. The thermal boundary resistance is demonstrated to be a major constraint on reaching low temperatures necessary to perform simultaneous inelastic electron tunneling and surface enhanced Raman spectroscopies.