Low‐Defect‐Density Monolayer MoS2 Wafer by Oxygen‐Assisted Growth‐Repair Strategy

Atomic chalcogen vacancy is the most commonly observed defect category in two dimensional (2D) transition‐metal dichalcogenides, which can be detrimental to the intrinsic properties and device performance. Here a low‐defect density, high‐uniform, wafer‐scale single crystal epitaxial technology by in situ oxygen‐incorporated “growth‐repair” strategy is reported. For the first time, the oxygen‐repairing efficiency on MoS2 monolayers at atomic scale is quantitatively evaluated. The sulfur defect density is greatly reduced from (2.71 ± 0.65) × 1013 down to (4.28 ± 0.27) × 1012 cm−2, which is one order of magnitude lower than reported as‐grown MoS2. Such prominent defect deduction is owing to the kinetically more favorable configuration of oxygen substitution and an increase in sulfur vacancy formation energy around oxygen‐incorporated sites by the first‐principle calculations. Furthermore, the sulfur vacancies induced donor defect states is largely eliminated confirmed by quenched defect‐related emission. The devices exhibit improved carrier mobility by more than three times up to 65.2 cm2 V−1 s−1 and lower Schottky barrier height reduced by half (less than 20 meV), originating from the suppressed Fermi‐level pinning effect from disorder‐induced gap state. The work provides an effective route toward engineering the intrinsic defect density and electronic states through modulating synthesis kinetics of 2D materials. The defect reduction efficiency via a facile “growth‐repair” strategy for MoS2 wafers is quantitatively investigated. A low sulfur defect density of 4.28 × 1012 cm−2 is achieved, which is caused by dramatic increase of defect formation energy neighboring substitutional oxygen atoms. The repaired MoS2 shows enhanced electrical and optical properties, paving the way toward future electronic and optoelectronic devices.