IN-PLANE THERMAL AND THERMOELECTRIC PROPERTIES OF POLYCRYSTALLINE HIGHLY PREFERRED ORIENTATION (W)_X(WSE_2)_Y_Z UPERLATTICE THIN FILMS

摘要

It was recently found by using the time domain thermal reflectance method that polycrystalline highly preferred orientation WSe_2 and [(W)_x(WSe_2)_y]_z superlattice films possess extremely low cross-plane thermal conductivity, which is desirable for thermal insulation and thermoelectric energy conversion applications. However, it is difficult to obtain the in-plane thermal conductivity by using the laser reflectance or the 3-ω method. Here we employ a suspended microdevice developed for measuring thermoelectric properties of individual nanowires and nanofilms to obtain the in-plane thermal conductivity, electrical conductivity, and Seebeck coefficient of [(W)_x(WSe_2)_y]_z superlattice films. The measurement results show that the in-plane thermal conductivities of these films are much higher than the cross-plane values, making the thermal conductivity of the films highly anisotropic.