A research team led by Prof. Young Hee LEE from the Institute for Basic Science successfully analyzed atomic structures and electrical characteristics of MoS 2 which are labeled as new materials for the next generation along with Graphene.
Grain boundaries in monolayer transition metal dichalcogenides have unique atomic defect structures and band dispersion relations that depend on the inter-domain misorientation angle. They explored misorientation angledependent electrical transport at grain boundaries in monolayer MoS 2 by correlating the atomic defect structures of measured devices analysed with transmission electron microscopy, and first-principles calculations. Transmission electron microscopy indicates that grain boundaries are primarily composed of 5–7 dislocation cores with periodicity and additional complex defects formed at high angles, obeying the classical low-angle theory. The inter-domain mobility is minimized for angles of 9° and increases nonlinearly by two orders of magnitude before saturating at 16 cm 2 V -1 s -1
around misorientation angle of 20°. This trend is explained via grain-boundary electrostatic barriers estimated from density functional calculations and experimental tunnelling barrier heights, which are 0.5 eV at low angles and 0.15 eV at high angles (≥20°). The results provide practical expectations regarding transport properties in large-area films, which are restricted largely by the poor mobility across low-angle grain boundaries. Also this work is applicable to other similar 2D systems and contribute to the fundamental understanding of transport in semiconductors. This research was published at Nature Communications, affiliated magazine with Nature.