Influence of defects and doping on phonon transport properties of monolayer MoSe2

The doping of monolayer MoSe2 by tungsten (W) can suppress the Se vacancy concentration, but how doping and resulting change in defect concentration can tune its thermal properties is not understood yet. We use first-principles density functional theory (DFT) along with the phonon Boltzmann transport equation (BTE) to study the phonon transport properties of pristine MoSe2 and W doped MoSe2 with and without the presence of Se vacancies. We found that for samples without Se vacancy, the W doping could enhance the thermal transport of monolayer MoSe2 due to reduced three-phonon scattering phase space. For example, we observed that the 16.7% W doping increases the thermal conductivity of the monolayer MoSe2 with 2% Se vacancy by 80% if all vacancies can be suppressed by W-doping. However, the W doping in the defective MoSe2 amplifies the influence of the phonon scattering caused by the Se vacancies, which results in a further decrease in thermal conductivity of monolayer MoSe2 with defects. This is found to be related with higher phonon density of states of Mo0.83W0.17Se2 and larger mass difference between W and Se atoms compared to Mo and Se atoms. This study deciphers the effect of defects and doping on the thermal conductivity of monolayer MoSe2, which helps us understand the mechanism of defect-induced phonon transport, and provides insights into enhancing the heat dissipation in MoSe2-based electronic devices.