Point defects in monolayer WSi<sub>2</sub>N<sub>4</sub> and MoSi<sub>2</sub>N<sub>4</sub>.
basic_science · Level V
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- Record sourced from PubMed, PMID 41872233.
- Also identified by DOI 10.1038/s41467-026-70946-7.
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Abstract
Point defects critically govern the properties of two-dimensional semiconductors, yet their atomic-scale characteristics in the emerging MoSi<sub>2</sub>N<sub>4</sub> family remain unexplored. Here we combine atomic-resolution scanning transmission electron microscopy and first-principles calculations to systematically investigate point defects in monolayer semiconducting WSi<sub>2</sub>N<sub>4</sub> and MoSi<sub>2</sub>N<sub>4</sub>. We identify ten distinct defect types, with Si-for-top-N antisites (Si<sub>N(t)</sub>), double-middle-N divacancies (V<sub>N(m)2</sub>), and double-top-N divacancies (V<sub>N(t)2</sub>) being the most abundant. These defects induce mobility modulation and bandgap reduction - in some cases leading to complete band closure and insulator-to-metal transitions - and, in certain configurations, give rise to spin-polarized bands with localized magnetic moments. Additionally, we observe low-dimensional assemblies formed via defect self-organization, including 2D Si<sub>N(t)</sub> networks and 1D Si2<sub>Mo</sub> chains. Our findings establish fundamental defect-property relationships and provide insights for defect-driven engineering of electronic and magnetic states in 2D WSi<sub>2</sub>N<sub>4</sub> and MoSi<sub>2</sub>N<sub>4</sub> semiconductors.