Thermal Conductivity of b-tungsten Nanofilms and Interface Thermal Resistance Between b-tungsten Sublayers

Abstract

In this work, the thermal transport properties of -phase tungsten (-W) nanofilms are characterized both in the in-plane and cross-plane directions. Two groups of samples are prepared, single-layered -W and multilayered -W. For the single-layered samples, the cross-plane thermal conductivity (kc) is studied by using the photothermal (PT) technique. kc of -W films is determined at 1.98 Wm-1K-1 , which is much smaller than that of the common -phase tungsten (174 Wm-1K-1). This small value is consistent with the large electrical resistivity reported for -W in literature. The in-plane thermal conductivity (ka) is studied by using the four-probe method combined with the Wiedemann-Franz law. ka ranges from 2.9 Wm-1K-1 to 3.5 Wm-1K-1, about 50% larger than that of kc, showing the clear anisotropic thermal transport property of the -W films. The PT technique is also employed on the multilayered samples. With the determined kc, we are able to obtain the interface thermal resistance (RW/W) between -W layers. The determined RW/W varies from 0.3 × 10-9 Km2W-1 to 6.9 × 10-9 Km2W-1, with an average value of 3 × 10-9 Km2W-1. This -W/-W interface thermal resistance is relatively small, indicating sound thermal contact between -W layers.