On September 15, 2021, our work “High and anomalous thermal conductivity in Monolayer MSi2Z4 Semiconductors has been published online by ACS Applied Materials & Interfaces. https://doi.org/10.1021/acsami.1c14205

Congratulations to our PhD student Yan Yin !

Two-dimensional(2D) semiconductors with high thermal conductivity (κ) are critical for keeping nanoelectronic devicescool by removing the high-density dissipation. 2D MoSi2N4 is one kind of novel two dimensional materials, which has been successfully synthesized by Chemical Vapor Deposition (CVD). In the large MA2Z4 family there exist affluent and interesting physical and chemical properties. However, The mystery of its thermal conductive properties still remains to be explored.

Lattice thermal conductivity of 2D MSi2Z4 and other 2D materials.

Anomalous 𝜅 of MSi2Z4 varying with average mass and Debye temperature

Recently, through density of functional theory and phonon Boltzmann transport equation, we explored eight 2D MSi2Z4 (M=Mo, Cr, W, Ti, Zr, Hf, and Z=N, P, As) semiconductors in terms of their structures, phononic nature, and thermal transport properties, and found that
1) 𝜅 of MoSi2N4 and WSi2N4 is found over 400 W/m/K at 300 K, which is higher than that in most of other 2D semiconductors and comparable to that of the good thermal conductor copper.
2) Z atom plays an effective role in controlling the thermal management of MoSi2Z4, i.e., 𝜅 of MoSi2Z4 decreasing by one order of magnitude from Z=N to Z=As.
3) In MSi2N4 (M=Mo, Cr, W, Ti, Zr, Hf), the variation of 𝜅 with respect to M is anomalous and the conventional guideline for searching high 𝜅 breaks down. The abnormality could be traced to an interplay of certain basic vibrational properties including the bunching strength and flatness of acoustic branches and their nearby optical branches, which lies outside of the conventional guidelines.

In short, our work has identified 2D semiconductor MSi2N4 as high-𝜅 materials, which could open new opportunities for heat dissipation and thermal management in semiconductor device, and give important insights into analyzing the physics of 𝜅 in layered 2D systems.