[Seminar] GS. Philippe Dollfus, lúc 14:30, ngày 19/07/2019 tại Đại học PHENIKAA
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Người trình bày: GS. Philippe Dollfus CNRS, Université Paris-Sud, Université Paris-Saclay, France.
Thời gian: 14:30, ngày 19/07/2019.
Địa điểm: Phòng 101, nhà B, Đại học Phenikaa Yên Nghĩa, Hà Đông, Hà Nội
Tiêu đề: Band structure engineering in 2D materials and their heterostructures – Application to nanoelectronics
The family of 2D materials is now very large. The combination of such materials, in the form of either vertical stack or in-plane heterostructure, offers an infinity of opportunities to engineer the band structure for specific applications.
For instance, to modulate the electronic and transport properties of graphene, a very attractive route consists in arranging properly two graphene sections of different orientation. One may think about strain junctions, twisted graphene bilayers and grain boundaries separating two crystalline graphene domains. Strain may be also used as an additional degree of freedom to tune differently the bandstructure of the two sections, as a consequence of the separation of their Dirac cones in k-space.
We will investigate these different options and their possible applications, by means of atomistic calculations combining Green’s functions (GF) and tight-binding (TB) formalisms, and including strain effects. We show in particular the possibility to tune in a wide range the conductance gap, though the two graphene sections remain gapless. In addition to the description of this effect, we will show how it can be to enhance the negative differential conductance in PN tunnel diodes, and to enhance the saturation and the on/off current ratio in transistors. In the case of polycrystalline graphene we show also that the transmission can be modulated differently by strain in the two valleys D and D’, which gives the possibility to manipulate valley-polarized currents and the optical-like behaviour of Dirac particles, even at room temperature.
Finally, we will show how heterostructures of transition metal dichalcogenides may be engineered to strongly improve the switching behaviour of tunnel field-effect transistors for low-power electronics.
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