Abstract
Low-symmetry two-dimensional (2D) materials have exhibited novel anisotropic properties in optics, electronics, and mechanics. Such characteristics have opened up new avenues for fundamental research on nano-electronic devices. In-plane thermal conductivity plays a pivotal role in the electronic performance of devices. This article reports a systematic study of the in-plane anisotropic thermal conductivity of PdSe2 with a pentagonal, low-symmetry structure. An in-plane anisotropic ratio up to 1.42 was observed by the micro-Raman thermometry method. In the Raman scattering spectrum, we extracted a frequency shift from the Ag3 mode with the most sensitivity to temperature. The anisotropic thermal conductivity was deduced by analyzing the heat diffusion equations of suspended PdSe2 films. With the increase in thickness, the anisotropy ratio decreased gradually because the thermal conductivity in the x-direction increased faster than in the y-direction. The anisotropic thermal conductivity provides thermal management strategies for the next generation of nano-electronic devices based on PdSe2.
Highlights
Two-dimensional (2D) materials have rapidly attracted widespread attention as promising materials for their novel physical properties and dramatic application prospects [1,2,3,4]
The layer-dependent anisotropic thermal conductivity of PdSe2 was the first demonstration of 2D noble-metal dichalcogenides (NMDCs), which is of great significance for the thermal management of the generation of PdSe2 -based electronic devices
Typical layered structures had a single thickness of 6 Å [7], and each layer was coupled with a powerful van der Waals force (190 meV/atom) [21]
Summary
Two-dimensional (2D) materials have rapidly attracted widespread attention as promising materials for their novel physical properties and dramatic application prospects [1,2,3,4]. PdSe2 possesses an infrequently puckered low-symmetry pentagonal, layered structure This unique atomic arrangement leads to interesting mechanical properties, including unusual negative Poisson’s ratio and ultra-high mechanical strength [12,13,14,15]. This low-symmetry structure offers new characteristics for in-plane anisotropy in optics and electronics [16,17]. It has been forecasted that, in the in-plane directions, the carrier mobility along the x-direction would be greater than along the y-direction, yet thermal conductivity was the opposite [22] This unique property indicates that PdSe2 has significant potential for thermoelectric applications, probably providing greater freedom in the thermal nano-devices’ design [21,22,23,24,25]. The layer-dependent anisotropic thermal conductivity of PdSe2 was the first demonstration of 2D NMDCs, which is of great significance for the thermal management of the generation of PdSe2 -based electronic devices
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