Unusually high thermal conductivity in suspended monolayer MoSi₂N₄

Two-dimensional semiconductors with high thermal conductivity and charge carrier mobility are vital for next-generation electronic and optoelectronic devices. Conventional 2D semiconductors (e.g., monolayer MoS₂, WS₂, MoSe₂, WSe₂, black phosphorus) have thermal conductivities lower than silicon (~142 W·m⁻¹·K⁻¹) due to complex crystal structures, large average atomic mass and relatively weak bonds. Monolayer MoSi₂N₄, despite its complex structure, has been predicted to combine high mobility and high thermal conductivity. Using a noncontact optothermal Raman technique, this work experimentally measures a high room-temperature thermal conductivity of ~173 W·m⁻¹·K⁻¹ for suspended monolayer MoSi₂N₄ grown by chemical vapor deposition. First-principles calculations attribute this unusually high thermal conductivity to a high Debye temperature and a small Grüneisen parameter, both strongly linked to the high Young’s modulus induced by the outermost Si–N bilayers. The study benchmarks monolayer MoSi₂N₄ as a high-performance 2D semiconductor and provides insights for designing efficient heat-conducting 2D materials.

Chengjian He, Chuan Xu, Chen Chen, Jinmeng Tong, Tianya Zhou, Su Sun, Zhibo Liu, Hui-Ming Cheng, Wencai Ren