Anisotropic thermal conductivity of nanocolumnar W thin films

We report on thermal conductivity of W films 350 nm thick sputter-deposited by glancing angle deposition (GLAD). The 3 omega method is used to measure the in-plane thermal conductivity k(x) and k(y) for films deposited with a deposition angle alpha of 0 degrees and 80 degrees. For classical films (alpha = 0 degrees), the thermal conductivity is 71 W m(-1) K-1, whereas for GLAD films (alpha = 80 degrees) the in-plane conduction drops to k(x) = 3.2 W m(-1) K-1 and k(y) = 4.8 W m(-1) K-1. The in-plane thermal conductivity anisotropy corresponds to a heat conduction favored in the direction perpendicular to the deposition axis, which is related to the anisotropic columnar microstructure. Electrical conductivity is also determined leading to a significant deviation from the Wiedemann-Franz law for the GLAD films. (C) 2021 Elsevier B.V. All rights reserved.