Record setting high in-plane thermal conductivity of AlN thin films enabled by SSTR measurements – Paper publishes in ACS Nano – Congrats Shafkat!

Congrats to Shafkat bin Hoque for your recent first author paper in ACS Nano reporting on the exceptionally high in-plane thermal conductivity of AlN thin films. We used SSTR to measure the in plane thermal conductivity of thin AlN films, and demonstrated that the in plane thermal conductivities of these AlN films are record setting, exceeding the heat spreading ability of even diamond.

Hoque, Md.S.B., Koh, Y.R., Braun, J.L., Mamun, A., Liu, Z., Huynh, K., Liao, M.E., Hussain, K., Cheng, Z., Hoglund, E.R., Olson, D.H., Tomko, J.A., Aryana, K., Galib, R., Gaskins, J.T., Elahi, M.M.M., Leseman, Z.C., Howe, J.M., Luo, T., Graham, S., Goorsky, M.S., Khan, A., Hopkins, P.E., “High in-plane thermal conductivity of aluminum nitride thin films,” ACS Nano 15, 9588-9599 (2021). PDF (Supporting Information).

Abstract: High thermal conductivity materials show promise for thermal mitigation and heat removal in devices. However, shrinking the length scales of these materials often leads to significant reductions in thermal conductivities, thus invalidating their applicability to functional devices. In this work, we report on high in-plane thermal conductivities of 3.05, 3.75, and 6 μm thick aluminum nitride (AlN) films measured via steady-state thermoreflectance. At room temperature, the AlN films possess an in-plane thermal conductivity of ∼260 ± 40 W m−1 K−1, one of the highest reported to date for any thin film material of equivalent thickness. At low temperatures, the in-plane thermal conductivities of the AlN films surpass even those of diamond thin films. Phonon−phonon scattering drives the in-plane thermal transport of these AlN thin films, leading to an increase in thermal conductivity as temperature decreases. This is opposite of what is observed in traditional high thermal conductivity thin films, where boundaries and defects that arise from film growth cause a thermal conductivity reduction with decreasing temperature. This study provides insight into the interplay among boundary, defect, and phonon−phonon scattering that drives the high in-plane thermal conductivity of the AlN thin films and demonstrates that these AlN films are promising materials for heat spreaders in electronic devices.

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