Abstract
Engineering thermal transport in two dimensional materials, alloys and heterostructures is critical for the design of next-generation flexible optoelectronic and energy harvesting devices. Direct experimental characterization of lattice thermal conductivity in these ultra-thin systems is challenging and the impact of dopant atoms and hetero-phase interfaces, introduced unintentionally during synthesis or as part of deliberate material design, on thermal transport properties is not understood. Here, we use non-equilibrium molecular dynamics simulations to calculate lattice thermal conductivity of {mathrm {(Mo|W)Se_2}} monolayer crystals including {mathrm {Mo}}_{1-x}{mathrm {W}}_x{mathrm {Se_2}} alloys with substitutional point defects, periodic {mathrm {MoSe_2}|mathrm {WSe_2}} heterostructures with characteristic length scales and scale-free fractal {mathrm {MoSe_2}}|{mathrm {WSe_2}} heterostructures. Each of these features has a distinct effect on phonon propagation in the crystal, which can be used to design fractal and periodic alloy structures with highly tunable thermal conductivities. This control over lattice thermal conductivity will enable applications ranging from thermal barriers to thermoelectrics.
Highlights
Engineering thermal transport in two dimensional materials, alloys and heterostructures is critical for the design of next-generation flexible optoelectronic and energy harvesting devices
Substitutional doping of MoSe2 by W atoms has a significant effect on the lattice thermal conductivity
Classical molecular dynamics simulations exclude electronic structure effects such as charge-transfer and charge carrier–phonon interactions, the large reduction in κlattice is attributable primarily to increased rate of point defect scattering that originates from both the mass difference and inter-atomic coupling force differences resulting in greater phonon localization and reduced mean-free paths[42,43,44]
Summary
Engineering thermal transport in two dimensional materials, alloys and heterostructures is critical for the design of next-generation flexible optoelectronic and energy harvesting devices. We use non-equilibrium molecular dynamics simulations to compute lattice thermal conductivity of monolayer (Mo|W)Se2 systems, including Mo1−x Wx Se2 alloys and fractal heterostructures and periodic superlattices constructed out of two transition metal dichalcogenides, MoSe2 and WSe2 , suitable for ultra-thin electronic applications. This distribution of point defects, hetero-phase interfaces and a range of feature sizes. Allows us to explore the influence of each of these features on phonon scattering and identify guidelines for design of two-dimensional material structures with tunable thermal transport properties
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