Thermal conductance of epitaxial interfaces

The thermal conductance of interfaces between epitaxial TiN and single crystal oxides is measured at temperatures between 79.4 and 294 K using time-domain thermoreflectance. The analysis method relies on the ratio of the in-phase and out-of-phase signals of the lock-in amplifier for more accurate data analysis. The validity of this approach is tested by measurements on 6.5, 11.8, and 25 nm thick thermally oxidized ${\mathrm{SiO}}_2$ on Si. The thermal conductances G of TiN/MgO(001), TiN/MgO(111), and ${\mathrm{T}\mathrm{i}\mathrm{N}/\mathrm{A}\mathrm{l}}_2{\mathrm{O}}_3\mathrm{}\left(0001\right)\mathrm{}$ interfaces are essentially identical and in good agreement with the predictions of lattice dynamics models and the diffuse mismatch model with a four-atom fcc unit cell. Near room temperature, $G\approx 700{\mathrm{M}\mathrm{W}\mathrm{m}}^{-2}{\mathrm{K}}^{-1},$ $\approx 5$ times larger than the highest values reported previously for any individual interface.