Manipulating the Thermal Conductivity of Monolayer MoS2 via Lattice Defect and Strain Engineering

Monolayer molybdenum disulfide (MoS2), a new two-dimensional material beyond graphene, has attracted tremendous attention recently. Its applications in nanoelectronic and thermoelectric devices usually require manipulating the thermal transport properties. Using nonequilibrium molecular dynamics simulations, we investigated the effects of lattice defects and mechanical strain on the thermal conductivity of MoS2. We found that the thermal conductivity of monolayer MoS2 can be effectively tuned by introducing even a small amount of lattice defects. For example, a 0.5% concentration of mono-Mo vacancies is able to reduce the thermal conductivity by about 60%. Remarkably, the thermal conductivity of the defected sample can further be tuned by mechanical strain. For example, a 12% tensile strain is able to reduce the thermal conductivity by another 60%. We also found that the tensile strain exerts almost the same impact on the thermal conductivity of both pristine and defective MoS2, which signifies that there is no apparent coupling between defects and strain in affecting the thermal conductivity. Our analyses of the vibrational density of state and spectral energy density show that the underlying mechanisms for these drastic changes are (1) the reduction of the phonon relaxation time arising from phonon-defect scattering and (2) the reduction of the group velocity and heat capacity caused by tensile strain. Our findings here provide important insights and guidelines for the use of monolayer MoS2 in thermal management and thermoelectric devices.