2D Semiconductor TMDCs Synthesis for large scale

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Nanomaterial Application Devices

(Transistor, Photo-detector)

▶ Background and Motivation

The electronics and optoelectronics have been promising future research topic. Especially, Each low dimensional semiconductor has outstanding characteristics about those in the materials world. 2D materials without atomic bonds in the Z-axis are superior in electron characteristics. Because TMDCs have complementary optical absorption properties as well as electronic properties, those are also called as materials of dream. Our laboratory will demonstrate electronic and optoelectronic devices based on 2D materials with noble physical properties and break through the limitations that current industry faces.

▶ Large Scale TMDC growth using Metal-Organic Chemical Vapor Deposition

Metal-Organic CVD growth provides a unprecedented direction of high-quality monolayer TMDC film for the integration of multiple device patterning with different 2D material compositions and electrical properties on single substrate. Metal Source and Gas are precisely Controlled by individual MFCs

▶ Hybrid optoelectronic : 2D-0D photodetector

The 2D-0D hybrid optoelectronic system maximizes the photodetector characteristics such as responsivity (R), Detectivity (D*) employing the advantages of the light absorption of quantum dot material and the high mobility of two-dimensional material.

▶ 2D Hetero-structure Electronics I

We demonstrate that thermal treatment under ambient condition precisely controls the thickness of BP flake.
The thermal etching method utilizes the chemical reactivity of BP surface with oxygen and water molecules by the repeated formation and evaporation of phosphoric acid during thermal annealing. Field effect transistor of the thickness-modulated BP sheet by thermal etching method shows a high hole mobility and a high on−off ratio. The stability of the BP devices remained for 1 month under ambient condition without an additional protecting layer, resulting from the preservation of active BP layers below native surface phosphorus oxide.

▶ 2D Hetero-structure Electronics II

In this study, the relationship between photocurrent and the charge balance of electrons and holes in van der Waals heterojunctions is investigated. To observe this phenomenon, a p-WSe2/n-WS2/n-MoS2 heterojunction device with both p–n and n–n junctions is fabricated. The device can modulate the charge carrier balance between heterojunction layers to generate photocurrent upon illumination by selectively applying electrostatic doping to a specific layer. Using photocurrent mapping, the operating transition zones for the device is demonstrated, allowing to accurately identify the locations where photocurrent generates. Finally, the origins of flicker and shot noise at the different semiconductor interfaces are analyzed to understand their effect on the photoresponsivity and detectivity of unit active area (2.5 μm2, 𝝀 = 405 nm) in the p-WSe2/n-WS2/n-MoS2 heterojunction device.