Manipulating Thermal Transport of Atomically Thin Crystals via Multiscale Defects

Semiconducting two-dimensional (2D) materials such as transition-metal dichalcogenides (TMDs) have attracted tremendous interest toward near-future applications in nanoelectronics, optoelectronics and thermoelectrics. For those applications, both deeply understanding and actively tuning their thermal transport is of crucial importance in that it intimately impacts the thermal management and energy consumption of devices. Given with the ultra-thin nature of 2D materials, defect engineering becomes much more powerful, so it can be a strategic approach to manipulate their thermal conduction on demand where defect generally acts as a phonon scattering center. In this presentation, we report highly tunable thermal conductivity of monolayer molybdenum disulfide (MoS₂) via multiscale defects, <i>i.e.</i>, mesoscale grain boundaries and atomic-scale point defects. Experimentally, thermal conductivity of defect engineered MoS₂ is measured by opto-thermal Raman thermometry by monitoring the temperature and power dependences of corresponding Raman peak shift. We found that the thermal conductivity of single- and poly-crystalline monolayer MoS₂ can be manipulated by additionally introducing point defects which is highly controllable by helium ion beam irradiation. Furthermore, we can decouple the effects of point defects and grain boundaries by analysing single- and poly-crystalline specimen. Our work can provide important insight for controlling thermal properties of 2D materials and the use of monolayer TMDs in the thermal management in modern electronics and energy harvesting devices.