Plasmonic Nanoscale Temperature Shaping on a Single Titanium Nitride Nanostructure

Arbitrary shaping of temperature fields at the nanometer scale is an important goal in nanotechnology; this is challenging due to diffusive nature of heat transfer. In the present work, we have numerically demonstrated that spatial shaping of nanoscale temperature fields can be achieved by plasmonic heating of a single titanium nitride (TiN) nanostructure. A key feature of TiN is its low thermal conductivity (k_TiN = 29 [W m−1K−1]) compared with ordinary plasmonic metals such as Au (k_Au = 314 [W m−1K−1]). When localized surface plasmon resonance of a metal nanostructure is excited, light intensity will be converted to heat power density in the nanostructure via the Joule heating effect. For a gold nanoparticle, nonuniform spatial distributions of the heat power density will be disappeared due to the high thermal conductivity of Au; the nanoparticle surface will be entirely isothermal. In contrast, the spatial distributions of the heat power density can be clearly transcribed into temperature fields on a TiN nanostructure because heat dissipation is suppressed. In fact, we have revealed that highly localized temperature distributions can be selectively controlled around the TiN nanostructure in the several tens of nm spatial resolution depending on excitation wavelength. The present results indicate that the arbitrary temperature shaping at the nanometer scale can be achieved by designing the heat power density in TiN nanostructures in plasmonic heating, leading to unconventional thermofluidics and thermal chemical biology.