Journal
ACS NANO
Volume 7, Issue 12, Pages 10475-10481Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nn4052887
Keywords
metal dichalcogenide; dislocation; grain boundary; magnetism; two-dimensional material
Categories
Funding
- U.S. Army Research Office MURI grant [W911NF-11-1-0362]
- Robert Welch Foundation [C-1590]
- NSF [OCI-0959097]
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Grain boundaries (GBs) are structural imperfections that typically degrade the performance of materials. Here we show that dislocations and GBs in two-dimensional (2D) metal dichalcogenides MX2 (M = Mo, W; X = 5, Se) can actually improve the material by giving it a qualitatively new physical property: magnetism. The dislocations studied all display a substantial magnetic moment of similar to 1 Bohr magneton. In contrast, dislocations in other well-studied 2D materials are typically nonmagnetic. GBs composed of pentagon-heptagon pairs interact ferromagnetically and transition from semiconductor to half-metal or metal as a function of tilt angle and/or doping level. When the tilt angle exceeds 47 degrees, the structural energetics favor square-octagon pairs and the GB becomes an antiferromagnetic semiconductor. These exceptional magnetic properties arise from interplay of dislocation-induced localized states, doping, and locally unbalanced stoichiometry. Purposeful engineering of topological GBs may be able to convert MX2 into a promising 2D magnetic semiconductor.
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