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○ Title: Electronic Properties of Mixed-dimensional 2D/3D Heterostructures
○ Speaker: 홍 석 륜 교수님 (세종대학교)
○ Date/time: 2021. 8. 4. (Wed.) 4:00PM
○ 온라인 참여방법: 아래의 WebEx 링크 접속
○ Abstract: Graphene and other 2D materials such as transition metal dichalcogenides (TMDs) and metal monochalcogenides (MMCs) have attractive physical and chemical properties. For utilization of 2D materials as electronic devices, their mixed-dimensional van der Waals (vdW) heterostructures with 3D materials are receiving much attention. To understand electronic properties of these mixed-dimensional 2D/3D heterostructures, we have performed density functional theory calculations.
We investigate the reduction of the Fermi level pinning (FLP) at Au–MoS2 interfaces by atomic passivation on Au(111). Passivating atoms prevent the direct contact between Au(111) and MoS2, and thus FLP at Au–MoS2 interfaces is reduced by weak interaction between atom-passivated Au(111) and MoS2. Especially, FLP is greatly reduced at sulfur-passivated Au-MoS2 interfaces with the smallest binding energy. Furthermore, fluorine-passivated Au(111) can form ohmic contact with MoS2, representing almost zero Schottky barrier height (SBH). We suggest that SBH can be controlled depending on the passivating atoms on Au(111).
Next, we study atomic and electronic structures of the 2D/3D heterojunction between MoS2 and Si(100) by focusing on the contact behavior dependence on the interfacial structures. Calculations show that MoS2 and clean Si(100) form an almost n-type ohmic contact with small SBH due to strong covalent bonds between them, and that the contact between MoS2 and H-Si(100) makes a p–n heterojunction with weak vdW interactions. Such a difference in contact behaviors can be explained by different electric dipole formation at the heterojunction interfaces. Similarly, 2D/3D heterostructures between GaSe and Si(111) are investigated. GaSe forms n-type contact with c-Si(111) and thus Fermi level pinning occurs at GaSe/c-Si(111) interfaces with metal-induced gap states. In the case of GaSe/H-Si(111), we identify that the interfaces form p-n heterojunction, especially with type II band alignment. Overall, it is concluded that contact properties can be varied depending on the interfacial structures of 2D/3D semiconductor heterojunctions.
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