Improved Thermal Anisotropy of Multi-Layer Tungsten Telluride on Silicon Substrate

WTe(2), a low-symmetry transition metal dichalcogenide, has broad prospects in functional device applications due to its excellent physical properties. When WTe(2) flake is integrated into practical device structures, its anisotropic thermal transport could be affected greatly by the substrate, which matters a lot to the energy efficiency and functional performance of the device. To investigate the effect of SiO(2)/Si substrate, we carried out a comparative Raman thermometry study on a 50 nm-thick supported WTe(2) flake (with κ(zigzag) = 62.17 W·m(−1)·K(−1) and κ(armchair) = 32.93 W·m(−1)·K(−1)), and a suspended WTe(2) flake of similar thickness (with κ(zigzag) = 4.45 W·m(−1)·K(−1), κ(armchair) = 4.10 W·m(−1)·K(−1)). The results show that the thermal anisotropy ratio of supported WTe(2) flake (κ(zigzag)/κ(armchair) ≈ 1.89) is about 1.7 times that of suspended WTe(2) flake (κ(zigzag)/κ(armchair) ≈ 1.09). Based on the low symmetry nature of the WTe(2) structure, it is speculated that the factors contributing to thermal conductivity (mechanical properties and anisotropic low-frequency phonons) may have affected the thermal conductivity of WTe(2) flake in an uneven manner when supported on a substrate. Our findings could contribute to the 2D anisotropy physics and thermal transport study of functional devices based on WTe(2) and other low-symmetry materials, which helps solve the heat dissipation problem and optimize thermal/thermoelectric performance for practical electronic devices.