MoSi$_2$N$_4$-like crystals -- the new family of two-dimensional materials

TL;DR

MoSi$_2$N$_4$-like crystals are a newly identified family of two-dimensional materials with diverse electronic properties, high mobility, and complex structures, promising for future electronic applications.

Contribution

This paper introduces a new family of 2D materials based on MoSi$_2$N$_4$, classifies their electronic properties, and predicts numerous members with potential for advanced electronic devices.

Findings

MoSi$_2$N$_4$ is a synthesized septuple layer 2D semiconductor.

Members of this family can be metallic, magnetic, or semiconducting.

Predicted room-temperature mobility can reach up to 5×10^4 cm$^2$/V*s.

Abstract

Recently-synthesised MoSi$_2$N$_4$ is the first septuple layer two-dimensional material, which doesn't naturally occurs as a layered crystal, and has been obtained with CVD growth. It can be considered as MoN$_2$ crystal (with a crystal structure of MoS2) intercalating Si2N2 two-dimensional layer (with the structure similar to InSe). Such classification gave rise to the understanding of the electronic properties of the material, but also to the prediction of other members of the family (many dozens of them) as well as to the way to classify those. Whereas the originally-synthesised MoSi$_2$N$_4$ is a semiconductor, some of the members of the family are also metallic and some even demonstrate magnetic properties. Interestingly, the room-temperature mobility predicted for such crystals can be as high few thousands cm$^2$/V*s (hole mobility typically higher than electron) with some record cases as high as $5\times 10^4$ cm$^2$/V*s, making these materials strong contenders for future electronic applications. The major interest towards these materials is coming from the septuple layer structure, which allows multiple crystal phases, but also complex compositions, in particular those with broken mirror-reflection symmetry against the layer of metal atoms.