In-Plane Anisotropic Thermal Conductivity of Low-Symmetry PdSe2

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 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.

Strain-Driven Switchable Thermal Conductivity in Ferroelastic PdSe2

“…There is an order of magnitude difference between the two structures. At the same time, Chen et al have measured that the κ L values of structure I with 1.62 and 7.20 nm thick nanosheets along the x and y axes are 10.95 and 15.08, and 25.35 and 28.45 W/mK in the experiment, respectively . The results are in good agreement with our calculational results, as shown in Figure a.…”

“…Compressive strain-dependent κ L (a) and total energy (b) along the x and y axes of ferroelastic phase transition (FPT) in layered PdSe 2 . At room temperature, rhomboid is the computational results in this work, while triangle and pentagram are the experimental measurements for 1.62 and 7.20 nm thick nanosheets under no strain in (a). The black dash line shows the energy level in (b).…”

Giant anisotropic in-plane thermal conduction induced by Anomalous phonons in pentagonal PdSe2

“…Table I lists the anisotropy of IPTC in the materials shown in Figure 4b, which shows the unique anisotropy in IPTC of PdSe2, i.e., high IPTC anisotropy with nearly-equal in-plane lattice constants and the nearly-isotropic bonding. It should be mentioned that our calculation shows a moderate difference with the measurement in PdSe2, where an anisotropy ratio of IPTC up to 1.42 was reported [24]. There could be two reasons that caused this discrepancy: (1) The bulk crystal model instead of the multilayer was used here for the calculation to adapt to our IXS experiment because phonon dispersions play a crucial role in computing the correct thermal conductivity [50].…”

“…Anisotropy of PdSe2 has also been reported, such as electrical [19,20], optical [15,19], and thermoelectric properties [16,21]. Much work has focused on the theoretical lattice dynamics calculations, but less was confirmed by measurements [22][23][24]. PdSe2 takes a puckered pentagonal structure with an orthorhombic lattice (a=5.75 Å, b=5.87 Å, c=7.69 Å, a/b=0.98) (Figure 1a) [25], in which four Se atoms covalently bond the Pd atom with a nearlyequal Pd-Se bond length (2.44 Å / 2.44 Å ≈ 1), bond strength (2.51 eV /2.50 eV ≈ 1), and bond force constant (4.18 eV Å -2 / 4.15 eV Å -2 ≈ 1) [26], showing a nearly-isotropic structure in the basal plane (Figure 1b).…”

Van der Waals MoS2/PdSe2 Heterostructures Grown by Chemical Vapor Deposition for Broadband and Polarized Photodetection

“…Specifically, it also possesses a pentagonal puckered structure which endows it strong in‐plane anisotropic mechanical, optical, electrical, and thermal properties. [ 21,26 ] For photodetection, the PdSe 2 NIR photodetector shows a photoresponsivity of 660 A W −1 under 914 nm laser and the electrical property after 6 months keeping in the air show little change as published by Prof. Duan. [ 27 ] Meanwhile, the PdSe 2 ‐based photodetector has exhibited competitive capability for polarized light detection with robust linearly dichroic ratios.…”