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Dappe YJ, Almadori Y, Dau MT, Vergnaud C, Jamet M, Paillet C, Journot T, Hyot B, Pochet P, Grévin B. Charge transfers and charged defects in WSe 2/graphene-SiC interfaces. Nanotechnology 2020; 31:255709. [PMID: 32182596 DOI: 10.1088/1361-6528/ab8083] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We report on Kelvin probe force microscopy (KPFM) and density functional theory (DFT) investigations of charge transfers in vertical heterojunctions between tungsten diselenide (WSe2) layers and graphene on silicon carbide substrates. The experimental data reveal the existence of an interface dipole, which is shown by DFT to originate from the neutralization of the graphene n-doping by an electron transfer towards the transition metal dichalcogenide (TMD) layer. The relative vacuum level shift probed by KPFM between the TMD and the substrate stays constant when passing from monolayer to bilayer graphene, which confirms that the Schottky-Mott model can be rigorously applied to these interfaces by taking into account the charge transfer from the substrate to the TMD. DFT calculations show that the first TMD layer absorbs almost all the excess charges contained in the graphene, and that the second TMD layer shall not play a significant role in the electrostatics of the system. Negatively charged defect at the TMD edges contribute however to the electrostatic landscape probed by KPFM on both TMD layers.
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Affiliation(s)
- Y J Dappe
- SPEC, CEA, CNRS, Université Paris Saclay, CEA Saclay, 91191 Gif-sur-Yvette Cedex France
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Oyarzún S, Nandy AK, Rortais F, Rojas-Sánchez JC, Dau MT, Noël P, Laczkowski P, Pouget S, Okuno H, Vila L, Vergnaud C, Beigné C, Marty A, Attané JP, Gambarelli S, George JM, Jaffrès H, Blügel S, Jamet M. Evidence for spin-to-charge conversion by Rashba coupling in metallic states at the Fe/Ge(111) interface. Nat Commun 2016; 7:13857. [PMID: 27976747 PMCID: PMC5171917 DOI: 10.1038/ncomms13857] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 11/04/2016] [Indexed: 12/13/2022] Open
Abstract
The spin-orbit coupling relating the electron spin and momentum allows for spin generation, detection and manipulation. It thus fulfils the three basic functions of the spin field-effect transistor. However, the spin Hall effect in bulk germanium is too weak to produce spin currents, whereas large Rashba effect at Ge(111) surfaces covered with heavy metals could generate spin-polarized currents. The Rashba spin splitting can actually be as large as hundreds of meV. Here we show a giant spin-to-charge conversion in metallic states at the Fe/Ge(111) interface due to the Rashba coupling. We generate very large charge currents by direct spin pumping into the interface states from 20 K to room temperature. The presence of these metallic states at the Fe/Ge(111) interface is demonstrated by first-principles electronic structure calculations. By this, we demonstrate how to take advantage of the spin-orbit coupling for the development of the spin field-effect transistor.
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Affiliation(s)
- S Oyarzún
- Institut des Nanosciences et l'Energie Atomique et Cryogénie, INAC, Commissariat á aux Energies Alternatives-Univ. Grenoble Alpes, 17 rue des Martyrs, F-38000 Grenoble, France
- CEA, INAC, F-38000 Grenoble, France
- Departamento de Fisica, CEDENNA, Universidad de Santiago de Chile (USACH), 9170124 Santiago, Chile
| | - A K Nandy
- Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
| | - F Rortais
- Institut des Nanosciences et l'Energie Atomique et Cryogénie, INAC, Commissariat á aux Energies Alternatives-Univ. Grenoble Alpes, 17 rue des Martyrs, F-38000 Grenoble, France
- CEA, INAC, F-38000 Grenoble, France
| | - J-C Rojas-Sánchez
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
| | - M-T Dau
- Institut des Nanosciences et l'Energie Atomique et Cryogénie, INAC, Commissariat á aux Energies Alternatives-Univ. Grenoble Alpes, 17 rue des Martyrs, F-38000 Grenoble, France
- CEA, INAC, F-38000 Grenoble, France
| | - P Noël
- Institut des Nanosciences et l'Energie Atomique et Cryogénie, INAC, Commissariat á aux Energies Alternatives-Univ. Grenoble Alpes, 17 rue des Martyrs, F-38000 Grenoble, France
- CEA, INAC, F-38000 Grenoble, France
| | - P Laczkowski
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
| | - S Pouget
- Institut des Nanosciences et l'Energie Atomique et Cryogénie, INAC, Commissariat á aux Energies Alternatives-Univ. Grenoble Alpes, 17 rue des Martyrs, F-38000 Grenoble, France
- CEA, INAC, F-38000 Grenoble, France
| | - H Okuno
- Institut des Nanosciences et l'Energie Atomique et Cryogénie, INAC, Commissariat á aux Energies Alternatives-Univ. Grenoble Alpes, 17 rue des Martyrs, F-38000 Grenoble, France
- CEA, INAC, F-38000 Grenoble, France
| | - L Vila
- Institut des Nanosciences et l'Energie Atomique et Cryogénie, INAC, Commissariat á aux Energies Alternatives-Univ. Grenoble Alpes, 17 rue des Martyrs, F-38000 Grenoble, France
- CEA, INAC, F-38000 Grenoble, France
| | - C Vergnaud
- Institut des Nanosciences et l'Energie Atomique et Cryogénie, INAC, Commissariat á aux Energies Alternatives-Univ. Grenoble Alpes, 17 rue des Martyrs, F-38000 Grenoble, France
- CEA, INAC, F-38000 Grenoble, France
| | - C Beigné
- Institut des Nanosciences et l'Energie Atomique et Cryogénie, INAC, Commissariat á aux Energies Alternatives-Univ. Grenoble Alpes, 17 rue des Martyrs, F-38000 Grenoble, France
- CEA, INAC, F-38000 Grenoble, France
| | - A Marty
- Institut des Nanosciences et l'Energie Atomique et Cryogénie, INAC, Commissariat á aux Energies Alternatives-Univ. Grenoble Alpes, 17 rue des Martyrs, F-38000 Grenoble, France
- CEA, INAC, F-38000 Grenoble, France
| | - J-P Attané
- Institut des Nanosciences et l'Energie Atomique et Cryogénie, INAC, Commissariat á aux Energies Alternatives-Univ. Grenoble Alpes, 17 rue des Martyrs, F-38000 Grenoble, France
- CEA, INAC, F-38000 Grenoble, France
| | - S Gambarelli
- Institut des Nanosciences et l'Energie Atomique et Cryogénie, INAC, Commissariat á aux Energies Alternatives-Univ. Grenoble Alpes, 17 rue des Martyrs, F-38000 Grenoble, France
- CEA, INAC, F-38000 Grenoble, France
| | - J-M George
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
| | - H Jaffrès
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
| | - S Blügel
- Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
| | - M Jamet
- Institut des Nanosciences et l'Energie Atomique et Cryogénie, INAC, Commissariat á aux Energies Alternatives-Univ. Grenoble Alpes, 17 rue des Martyrs, F-38000 Grenoble, France
- CEA, INAC, F-38000 Grenoble, France
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