Facile and rigorous route to distinguish the boundary structure of monolayer MoS2 domains by oxygen etching

Chen

Tan

et al. 2022

ACS Appl. Nano Mater.

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Different transitional-metal dichalcogenides (TMDs) can form lateral heterojunctions by epitaxial growth. TMD heterojunctions exhibit unique optical and electrical properties by seamlessly connecting atoms at the interface. Bilayer (BL) TMDs with nanoscale thicknesses have higher state density, mobility, and room temperature stability than monolayer (ML) TMDs, so they may be more suitable for optoelectronic device applications. However, the synthesis of BL lateral heterojunctions is challenging due to the uncontrolled orientation of the second layer stacking. We report a method to grow lateral heterojunctions of BL TMDs by self-assembly epitaxy. The number of nucleation layers can be controlled by the Mo/S ratio. The BL lateral heterojunctions synthesized by this method are all AB stacking, which effectively avoids the simultaneous existence of vertical and lateral heterojunctions in AA′ stacking. After the alkaline precursor solution is spun, the binding ability of WO 4 2− or MoO 4 2− ions to sulfur atoms is different. Sulfur atoms preferentially combine with MoO 4 2− ions to form MoS 2 , resulting in a lateral heterojunction with a sharp interface. The BL lateral heterojunction has a better photoelectric detector performance than the ML. This work provides a method for the synthesis of BL lateral heterojunctions.

Section: Resultsmentioning

confidence: 99%

One-Step Synthesis of a Bilayer MoS₂/WS₂ Lateral Heterojunction for Photoelectric Detection

Chen

Tan

et al. 2022

ACS Appl. Nano Mater.

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“…[57] Etching technology has been widely used to study defects, GBs and boundary structures of 2D materials. [58][59][60] To further determine the seamless stitching of unidirectional MoS 2 domains, oxygen etching was performed to visualize the possible GBs on macroscopic scale. Figure 3b shows no obvious etching lines between unidirectional MoS 2 domains after oxygen etching, only some etched triangular pits appear inside the domains.…”

Section: Resultsmentioning

confidence: 99%

Single‐Crystal MoS₂ Monolayer Wafer Grown on Au (111) Film Substrates

Jiang

et al. 2021

Small

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Monolayer transition metal dichalcogenides (TMDCs) with high crystalline quality are important channel materials for next‐generation electronics. Researches on TMDCs have been accelerated by the development of chemical vapor deposition (CVD). However, antiparallel domains and twin grain boundaries (GBs) usually form in CVD synthesis due to the special threefold symmetry of TMDCs lattices. The existence of GBs severely reduces the electrical and photoelectrical properties of TMDCs, thus restricting their practical applications. Herein, the epitaxial growth of single crystal MoS2 (SC‐MoS2) monolayer is reported on Au (111) film across a two‐inch c‐plane sapphire wafer by CVD. The MoS2 domains obtained on Au (111) film exhibit unidirectional alignment with zigzag edges parallel to the <110> direction of Au (111). Experimental results indicated that the unidirectional growth of MoS2 domains on Au (111) is a temperature‐guided epitaxial growth mode. The high growth temperature provides enough energy for the rotation of the MoS2 seeds to find the most favorable orientation on Au (111) to achieve a unidirectional ratio of over 99%. Moreover, the unidirectional MoS2 domains seamlessly stitched into single crystal monolayer without GBs formation. The progress achieved in this work will promote the practical applications of TMDCs in microelectronics.

“…MoS 2 was synthesized using a multi-tube reactor, where the Mo source and S source were placed in different quartz tubes inside the quartz reactor, and the gas flow can be adjusted independently for each tube, which can effectively avoid Mo source poisoning in a low-pressure environment, as shown in Figure S1. In our previous work, 18 we have studied in detail the evolution of MoS 2 domain shape and boundary structure under thermodynamic equilibrium growth conditions. In order to synthesize the balanced growth of MoS 2 , we need to keep the growth parameters constant during the experiment.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Morphology Regulation of MoS₂ Nanosheet-Based Domain Boundaries for the Hydrogen Evolution Reaction

et al. 2022

ACS Appl. Nano Mater.

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The edge of the 2H-MoS2 phase has good electrocatalytic behavior for hydrogen evolution reaction (HER). However, the shape of monolayer MoS2 synthesized under thermodynamic equilibrium conditions is triangular, which limits the density of catalytic sites at the edge of a crystal domain. The morphology of the edge of monolayer MoS2 grown under non-thermodynamic equilibrium conditions will show a large number of dendrite nanostructures. The abundant dendrite edge nanostructures make it have more catalytic site densities than monolayer MoS2 synthesized under thermodynamic equilibrium conditions. The relationship between MoO3 source supply and MoS2 fractal dimension was established through the simulation of fractal dimension. HER performance showed that the Tafel slope (59 mV/Dec) of dendrite monolayer MoS2 was much lower than that of the triangular sample (97 mV/Dec), which confirmed that the dendrite MoS2 monolayer was more conducive to the application of hydrogen evolution reaction.