Temperature- and roughness-dependent permittivity of annealed/unannealed gold films

Abstract

Intrinsic absorption and subsequent heat generation have long been issues for metal-based plasmonics. Recently, thermo-plasmonics, which takes the advantage of such a thermal effect, is emerging as an important branch of plasmonics. However, although significant temperature increase is involved, characterization of metal permittivity at different temperatures and corresponding thermo-derivative are lacking. Here we measure gold permittivity from 300K to 570K, which the latter is enough for gold annealing. More than one order difference in thermo-derivative is revealed between annealed and unannealed films, resulting in a large variation of plasmonic properties. In addition, an unusual increase of imaginary permittivity after annealing is found. Both these effects can be attributed to the increased surface roughness incurred by annealing. Our results are valuable for characterizing extensively used unannealed nanoparticles, or annealed nanostructures, as building blocks in future thermo-nano-plasmonic systems.

Metal nanospheres under intense continuous-wave illumination: A unique case of nonperturbative nonlinear nanophotonics

“…where T 0 h is the temperature of the host away from the nanosphere. This was shown to be the case at least up to several hundreds of degrees in recent ellipsometry measurements of Au [12,13] thin films; the data in these studies was remarkably similar and was in excellent agreement with an earlier study [10] performed over a narrower temperature range. Similar behaviour was also seen for a Ag film [11], which describes probably the most detailed study, to date, of the temperature dependence of the Ag permittivity (in terms of wavelength and temperature range); it also includes an attempt to eliminate the effects of roughness, and is complemented with a first-principles calculation of the permittivity.…”

“…In that sense, this study was motivated by recent measurements of the extremely strong scattering of intense CW light from small metal particles [5][6][7][8][9], which, although being conceptually simple, are first of their kind. Further, this study was made possible by recent ellipsometry measurements of metal permittivities at elevated temperatures [10][11][12][13]. Thus, although we present here rather simple theoretical calculations, we emphasize that the approach is quite realistic.…”

“…We set λ = 550nm such that ǫ Au,0 = −5.3 + 1.76i and B Au = (0.7 + 1.7i) · 10 −3 / • K [13] so that with a liquid host for which ǫ h = 2.65, the illumination is resonant. We also set…”

Thermal effects – an alternative mechanism for plasmon-assisted photocatalysis

“…[21,22] as well as the necessary temperature-dependent permittivity data presented in Refs. [23][24][25][26] and references therein.…”

Eppur Si Riscalda - and yet, It (Just) Heats Up: Further Comments on “Quantifying Hot Carrier and Thermal Contributions in Plasmonic Photocatalysis”

“…First, the absorption coefficient α depends on the temperature via the temperature dependence of the metal permittivity, an effect studied in countless papers, see e.g., [20,21] for the ultrafast temperature dependence of the metal permittivity; many other papers, including various ellipsometry papers, studied the corresponding steady-state temperature dependence, see e.g., [17,18,[22][23][24], to name just a few. Second, the heat transfer coefficient h(T ) also depends on the temperature via e.g., the thermal conductivity, Kapitza resistance etc.…”