Defect engineering for thermal transport properties of nanocrystalline molybdenum diselenide

S Sabbaghi and V Bazargan and E Hosseinian, NANOSCALE, 15, 12634-12647 (2023).

DOI: 10.1039/d3nr01839c

Molybdenum diselenide (MoSe2) is attracting great attention as a transition metal dichalcogenide (TMDC) due to its unique applications in micro-electronics and beyond. In this study, the role of defects in the thermal transport properties of single-layer MoSe2 is investigated using non-equilibrium molecular dynamics (NEMD) simulations. Specifically, this work quantifies how different microstructural defects such as vacancies and grain boundaries (GBs) and their concentration (N) alter the thermal conductivity (TC) of single crystal and nanocrystalline MoSe2. These results show a significant drop in thermal conductivity as the concentration of defects increases. Specifically, point defects lower the TC of MoSe2 in the form of N-& beta; where & beta; is 0.5, 0.48 and 0.36 for V-Mo, VMo-Se and V-Se vacancies, respectively. This study also examines the impact of grain boundaries on the thermal conductivity of nanocrystalline MoSe2. These results suggest that GB migration and stress-assisted twinning along with localized phase transformation (2H to 1T) are the primary factors affecting the thermal conductivity of nanocrystalline MoSe2. Based on MD simulations, TC of polycrystalline MoSe2 increases with the average grain size (d) in the form of d(4.5). For example, the TC of nanocrystalline MoSe2 with d = 11 nm is around 40% lower than the TC of the pristine monocrystalline sample with the same dimensions. Finally, the influence of sample size and temperature is studied to determine the sensitivity of quantitative thermal properties to the length scale and phonon scattering, respectively. The results of this work could provide valuable insights into the role of defects in engineering the thermal properties of next generation semiconductor-based devices.

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