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The fabrication of electronic devices from exfoliated 2-D materials can be tricky. The group of Daniel Granados at IMDEA Nanociencia has engineered a solution that consists of the after-fabrication tailoring of MoS2-FET transistors using pulsed-focused electron beam induced etching.
Transition metal dichalcogenides are 2-D, atomically thin layers bound together by Van der Waals forces. These materials exhibit thickness-dependent variations in their physical properties that can be exploited in distinct optoelectronic applications. For example, the band structure of molybdenum disulphide (MoS2) has a direct bandgap of 1.8 eV in a single layer that narrows down with thickness of 1.2 eV indirect bandgap in bulk.
Layers - MoS2 - Exfoliation - Fabrication - Devices
The atomically thin layers of MoS2 can be separated by micromechanical exfoliation, nonetheless the fabrication of optoelectronic devices from mechanically exfoliated MoS2 is an intricate process. The geometry of the device is limited in all cases by the shape of the exfoliated flake, even when a deterministic stamping method is employed. Even when using CVD (chemical vapour deposition) techniques the device fabrication is hindered by the material growing in islands with reduced sizes and different physical properties.
Thus, developing techniques to tailor the device geometry after the fabrication steps are completed is of great interest. The group of Prof. Daniel Granados at IMDEA Nanociencia has come to a smart solution by modifying the geometry of several field effect transistors (FET) fabricated out of exfoliated MoS2. The proposed method uses a variation of focused electron beam-induced etching (FEBIE) with a pulsed electron beam. The beam scans the surface into a designed...
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