Thermal Conductivity Of MoS₂ Thin Films By Molecular Dynamic Simulations

Due to remarkable physical properties, Molybdenum disulfide (MoS2) has recently been a focus of extensive research. It can be widely applied to the microelectronic, optoelectronic and biological medical devices. However, all of these applications are related to the management and control of the temperature. Therefore, the study of thermal transport properties of MoS2 is very important. Using molecular dynamic (MD) simulation methods, the thermal conductivity (?) and phonon transport properties in MoS2 thin films with different structures are calculated in this paper.The non-equilibrium MD simulation is employed to investigate the ? of monolayer MoS2. It is found that temperature and length can affect the ? of monolayer MoS2. The ? decreases with the temperature increased. With the increasing of the length, the ? increases fast at first, then slowly. The ? of MoS2 with the length 1.2?m is 104.7 W/mK. It is found that the 31.0% contribution of the ? comes from phonons with mean free path (MFPs) larger than 1 ?m. The effects of random isotopic doping concentration, isotopic type and temperature are considered in our study. It shows that the ? of MS2 decreases with the increasing concentration and reaches a minimum at a concentration of 50%.The non-equilibrium MD simulation is used to calculate the in-plane and out-plane ? of multilayer MoS2. We find that the number of layers and boundary conditions do not have obvious effect on the in-plane ?. But the increasing interlayer coupling strength can decreases ? very slowly. Layers, temperature and strain can affect the out-plane ?. The results show the temperature and ? are negatively correlated. When the thickness is less than the phonon MFPs, the ? increases with the size increased. When the thickness is much larger than the phonon MFPs, the ? tends to converge. Cumulative function of ? indicates that phonons with MFPs smaller than 40 nm contribute 90% of the out-plane ?. The shorter cross-plane phonon MFPs in bulk MoS2 may result from the lower phonon cut-off frequency and the mismatch of phonon DOS. It is also found that the increasing strain can increase the interfacial thermal resistance.