Thermal Studies of Au–BaTiO₃ Nanoscale Hybrid Metamaterial

With embedded periodic vertical nanopillars, oxide-metal nanocomposite thin films hold significant potential for various applications, including magnetic data storage, energy storage, plasmonics, optics, sensors, multiferroics, and spintronics.¹ In these thin films, electron-phonon coupling at the metal-oxide interface plays a crucial role in restricting the in-plane thermal transport. When the corresponding interfacial resistance becomes a critical factor, these thin films become particularly intriguing when compared to extensively studied periodic nanoporous thin films. In general, such periodic structures are used for both photonics and phononics devices, where periodic nanostructures are used to manipulate the wave propagation within the structure by tuning the dispersion relation of photons and phonons. The interplay between optical photons and phonons also leads to important applications such as optomechanical waveguides and resonators.²<br/>This study focuses on systematically measuring the in-plane thermal conductivity of Au-BaTiO₃ nanocomposite thin films with sub-100 nm feature sizes.³ The measured samples are fabricated as a metal-coated suspended bridge for 3 omega measurements⁴ to extract both the specific heat and in-plane thermal conductivity. Thermal analysis is further carried out to gain a deeper understanding of thermal transport across the metal-oxide interface and within the periodic patterns. Transmission electron microscopy studies are carried out to reveal the defects at the metal-oxide interfaces, which may largely impact the thermal transport.⁵ Our study provides important guidance for the thermal management of the related plasmonic or other devices using these composite thin films.⁶<br/><br/>References:<br/>1 Misra, S. & Wang, H. Review on the growth, properties and applications of self-assembled oxide–metal vertically aligned nanocomposite thin films—current and future perspectives. <i>Materials Horizons</i> <b>8</b>, 869-884 (2021).<br/>2 Safavi-Naeini, A. H., Van Thourhout, D., Baets, R. & Van Laer, R. Controlling phonons and photons at the wavelength scale: integrated photonics meets integrated phononics. <i>Optica</i> <b>6</b>, 213-232 (2019).<br/>3 Zhang, D., Qi, Z., Jian, J., Huang, J., Phuah, X. L., Zhang, X. & Wang, H. Thermally Stable Au–BaTiO3 Nanoscale Hybrid Metamaterial for High-Temperature Plasmonic Applications. <i>ACS Applied Nano Materials</i> <b>3</b>, 1431-1437 (2020).<br/>4 Hao, Q., Xu, D., Zhao, H., Xiao, Y. & Medina, F. J. Thermal Studies of Nanoporous Si Films with Pitches on the Order of 100 nm -Comparison between Different Pore-Drilling Techniques. <i>Scientific Reports</i> <b>8</b>, 9056 (2018).<br/>5 Giri, A., Walton, S. G., Tomko, J., Bhatt, N., Johnson, M. J., Boris, D. R., Lu, G., Caldwell, J. D., Prezhdo, O. V. & Hopkins, P. E. Ultrafast and Nanoscale Energy Transduction Mechanisms and Coupled Thermal Transport across Interfaces. <i>ACS Nano</i> <b>17</b>, 14253-14282 (2023).<br/>6 Cunha, J., Guo, T. L., Della Valle, G., Koya, A. N., Proietti Zaccaria, R. & Alabastri, A. Controlling light, heat, and vibrations in plasmonics and phononics. <i>Advanced Optical Materials</i> <b>8</b>, 2001225 (2020).