基于第一性原理的单层WS2热输运特性研究

二维WS₂是一种层状过渡金属硫化物，因其具有特殊的层状结构、可调带隙及稳定的物理化学性质而备受关注。结合玻尔兹曼输运方程(BTE)和密度泛函理论(DFT),利用第一性原理研究了单层WS₂声子的输运特性，分析了声子的谐性效应和非谐性效应对WS₂晶格热导率的影响机理，计算了其声子的临界平均自由程，提出通过调整阻断频率的方法来调控WS₂的晶格热导率。研究结果表明：单层WS₂在300 K时的本征晶格热导率为149.12 W/(m·K),且随温度的升高而降低；从各声子支对总热导率的贡献来看，声学声子支起主要作用，特别是纵向声学(longitudinal acoustic, LA)声子支对单层WS₂热导率的贡献百分比最大(44.28%);单层WS₂声学声子支和光学声子支之间的较大带隙(声光学声子支之间无散射)导致其具有较高的晶格热导率。本文研究可为基于单层WS₂纳米电子器件的设计和改进提供借鉴和理论指导。

First-Principles Investigation on Thermal Transport Properties of Monolayer WS2

As one kind of layered transition metal sulfides, Two-dimensional WS₂ has attracted much attention because of its special layered structure, tunable band gap and stable physicochemical properties. Combining Boltzmann transport equation (BTE) and density functional theory (DFT), the phonon transport properties of monolayer WS₂ were investigated by first-principles. The harmonic and anharmonic effects of phonons to the lattice thermal conductivity of WS₂ were analyzed. The critical mean free path of phonon for WS₂ was calculated, which demonstrated that the thermal conductivity of WS₂ could be regulated by adjusting the frequency. The results show that the intrinsic lattice thermal conductivity of monolayer WS₂ is 149.12 W/(m·K) at 300 K, and it will decrease with the increase of temperature. The acoustic phonon branches play a major role among all phonon branches to the total thermal conductivity of monolayer WS₂, especially the longitudinal acoustic (LA) branch whose contribution percentage is 44.28%. There is a big band gap (no scattering) between the acoustic and optical branches, which is found to be responsible for the higher lattice thermal conductivity of monolayer WS₂. This investigation could provide a reference and theoretical guidance for the design and improvement of monolayer WS₂ based nano-electronic devices.