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Hnid I, Yassin A, Arbouch I, Guérin D, van Dyck C, Sanguinet L, Lenfant S, Cornil J, Blanchard P, Vuillaume D. Molecular Junctions for Terahertz Switches and Detectors. NANO LETTERS 2024; 24:2553-2560. [PMID: 38363554 DOI: 10.1021/acs.nanolett.3c04602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/17/2024]
Abstract
Molecular electronics targets tiny devices exploiting the electronic properties of the molecular orbitals, which can be tailored and controlled by the chemical structure and configuration of the molecules. Many functional devices have been experimentally demonstrated; however, these devices were operated in the low-frequency domain (mainly dc to MHz). This represents a serious limitation for electronic applications, although molecular devices working in the THz regime have been theoretically predicted. Here, we experimentally demonstrate molecular THz switches at room temperature. The devices consist of self-assembled monolayers of molecules bearing two conjugated moieties coupled through a nonconjugated linker. These devices exhibit clear negative differential conductance behaviors (peaks in the current-voltage curves), as confirmed by ab initio simulations, which were reversibly suppressed under illumination with a 30 THz wave. We analyze how the THz switching behavior depends on the THz wave properties (power and frequency), and we benchmark that these molecular devices would outperform actual THz detectors.
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Affiliation(s)
- Imen Hnid
- Institute for Electronics Microelectronics and Nanotechnology (IEMN), CNRS, University of Lille, Av. Poincaré, F-59652 Villeneuve d'Ascq, France
| | - Ali Yassin
- MOLTECH-Anjou, CNRS, University of Angers, SFR MATRIX, F-49000 Angers, France
- Natural Sciences Department, School of Arts and Sciences, Lebanese American University, 1102-2801, Beirut, Lebanon
| | - Imane Arbouch
- Laboratory for Chemistry of Novel Materials, University of Mons, 7000 Mons, Belgium
| | - David Guérin
- Institute for Electronics Microelectronics and Nanotechnology (IEMN), CNRS, University of Lille, Av. Poincaré, F-59652 Villeneuve d'Ascq, France
| | - Colin van Dyck
- Theoretical Chemical Physics group, University of Mons, 7000 Mons, Belgium
| | - Lionel Sanguinet
- MOLTECH-Anjou, CNRS, University of Angers, SFR MATRIX, F-49000 Angers, France
| | - Stéphane Lenfant
- Institute for Electronics Microelectronics and Nanotechnology (IEMN), CNRS, University of Lille, Av. Poincaré, F-59652 Villeneuve d'Ascq, France
| | - Jérôme Cornil
- Laboratory for Chemistry of Novel Materials, University of Mons, 7000 Mons, Belgium
| | - Philippe Blanchard
- MOLTECH-Anjou, CNRS, University of Angers, SFR MATRIX, F-49000 Angers, France
| | - Dominique Vuillaume
- Institute for Electronics Microelectronics and Nanotechnology (IEMN), CNRS, University of Lille, Av. Poincaré, F-59652 Villeneuve d'Ascq, France
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Oswald J, Beretta D, Stiefel M, Furrer R, Lohde S, Vuillaume D, Calame M. Field and Thermal Emission Limited Charge Injection in Au-C60-Graphene van der Waals Vertical Heterostructures for Organic Electronics. ACS APPLIED NANO MATERIALS 2023; 6:9444-9452. [PMID: 37325015 PMCID: PMC10262147 DOI: 10.1021/acsanm.3c01090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Accepted: 05/08/2023] [Indexed: 06/17/2023]
Abstract
Among the family of 2D materials, graphene is the ideal candidate as top or interlayer electrode for hybrid van der Waals heterostructures made of organic thin films and 2D materials due to its high conductivity and mobility and its inherent ability of forming neat interfaces without diffusing in the adjacent organic layer. Understanding the charge injection mechanism at graphene/organic semiconductor interfaces is therefore crucial to develop organic electronic devices. In particular, Gr/C60 interfaces are promising building blocks for future n-type vertical organic transistors exploiting graphene as tunneling base electrode in a two back-to-back Gr/C60 Schottky diode configuration. This work delves into the charge transport mechanism across Au/C60/Gr vertical heterostructures fabricated on Si/SiO2 using a combination of techniques commonly used in the semiconductor industry, where a resist-free CVD graphene layer functions as a top electrode. Temperature-dependent electrical measurements show that the transport mechanism is injection limited and occurs via Fowler-Nordheim tunneling at low temperature, while it is dominated by a nonideal thermionic emission at room and high temperatures, with energy barriers at room temperature of ca. 0.58 and 0.65 eV at the Gr/C60 and Au/C60 interfaces, respectively. Impedance spectroscopy confirms that the organic semiconductor is depleted, and the energy band diagram results in two electron blocking interfaces. The resulting rectifying nature of the Gr/C60 interface could be exploited in organic hot electron transistors and vertical organic permeable-base transistors.
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Affiliation(s)
- Jacopo Oswald
- Transport
at Nanoscale Interfaces Laboratory, Empa
- Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland
- Swiss
Nanoscience Institute, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Davide Beretta
- Transport
at Nanoscale Interfaces Laboratory, Empa
- Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland
| | - Michael Stiefel
- Transport
at Nanoscale Interfaces Laboratory, Empa
- Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland
| | - Roman Furrer
- Transport
at Nanoscale Interfaces Laboratory, Empa
- Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland
| | - Sebastian Lohde
- Transport
at Nanoscale Interfaces Laboratory, Empa
- Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland
| | - Dominique Vuillaume
- Institute
of Electronic, Microelectronic and Nanotechnology (IEMN), Centre National de la Recherche Scientifique, Villeneuve d’Ascq 59652, France
| | - Michel Calame
- Transport
at Nanoscale Interfaces Laboratory, Empa
- Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland
- Swiss
Nanoscience Institute, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
- Department
of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
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Daher Mansour M, Oswald J, Beretta D, Stiefel M, Furrer R, Calame M, Vuillaume D. Nanoscale electronic transport at graphene/pentacene van der Waals interfaces. NANOSCALE 2023; 15:9203-9213. [PMID: 37157969 DOI: 10.1039/d2nr06682c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
We report a study on the relationship between the structure and electron transport properties of nanoscale graphene/pentacene interfaces. We fabricated graphene/pentacene interfaces from 10 to 30 nm thick needle-like pentacene nanostructures down to two-three layer (2L-3L) dendritic pentacene islands, and we measured their electron transport properties by conductive atomic force microscopy (C-AFM). The energy barrier at the interfaces, i.e., the energy position of the pentacene highest occupied molecular orbital (HOMO) with respect to the Fermi energy of graphene and the C-AFM metal tip was determined and discussed with an appropriate electron transport model (a double Schottky diode model and a Landauer-Buttiker model, respectively) taking into account the voltage-dependent charge doping of graphene. In both types of samples, the energy barrier at the graphene/pentacene interface is slightly larger than that at the pentacene/metal tip interface, resulting in 0.47-0.55 eV and 0.21-0.34 eV, respectively, for the 10-30 nm thick needle-like pentacene islands, and 0.92-1.44 eV and 0.67-1.05 eV, respectively, for the 2L-3L thick dendritic pentacene nanostructures. We attribute this difference to the molecular organization details of the pentacene/graphene heterostructures, with pentacene molecules lying flat on graphene in the needle-like pentacene nanostructures, while standing upright in the 2L-3L dendritic islands, as observed from Raman spectroscopy.
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Affiliation(s)
- Michel Daher Mansour
- Institut for Electronic, Microelectronic and Nanotechnology, Centre National de la Recherche Scientifique, Villeneuve d'Ascq, France.
| | - Jacopo Oswald
- Transport at Nanoscale Interfaces Laboratory, Swiss Federal Laboratories for Materials Science and Technology (EMPA), Dübendorf, Switzerland.
- Swiss Nanoscience Institute, University of Basel, Switzerland
| | - Davide Beretta
- Transport at Nanoscale Interfaces Laboratory, Swiss Federal Laboratories for Materials Science and Technology (EMPA), Dübendorf, Switzerland.
| | - Michael Stiefel
- Transport at Nanoscale Interfaces Laboratory, Swiss Federal Laboratories for Materials Science and Technology (EMPA), Dübendorf, Switzerland.
| | - Roman Furrer
- Transport at Nanoscale Interfaces Laboratory, Swiss Federal Laboratories for Materials Science and Technology (EMPA), Dübendorf, Switzerland.
| | - Michel Calame
- Transport at Nanoscale Interfaces Laboratory, Swiss Federal Laboratories for Materials Science and Technology (EMPA), Dübendorf, Switzerland.
- Swiss Nanoscience Institute, University of Basel, Switzerland
- Department of Physics, University of Basel, Switzerland
| | - Dominique Vuillaume
- Institut for Electronic, Microelectronic and Nanotechnology, Centre National de la Recherche Scientifique, Villeneuve d'Ascq, France.
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Oswald J, Beretta D, Stiefel M, Furrer R, Vuillaume D, Calame M. The Effect of C60 and Pentacene Adsorbates on the Electrical Properties of CVD Graphene on SiO 2. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:1134. [PMID: 36986028 PMCID: PMC10052095 DOI: 10.3390/nano13061134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 03/17/2023] [Accepted: 03/20/2023] [Indexed: 06/18/2023]
Abstract
Graphene is an excellent 2D material for vertical organic transistors electrodes due to its weak electrostatic screening and field-tunable work function, in addition to its high conductivity, flexibility and optical transparency. Nevertheless, the interaction between graphene and other carbon-based materials, including small organic molecules, can affect the graphene electrical properties and therefore, the device performances. This work investigates the effects of thermally evaporated C60 (n-type) and Pentacene (p-type) thin films on the in-plane charge transport properties of large area CVD graphene under vacuum. This study was performed on a population of 300 graphene field effect transistors. The output characteristic of the transistors revealed that a C60 thin film adsorbate increased the graphene hole density by (1.65 ± 0.36) × 1012 cm-2, whereas a Pentacene thin film increased the graphene electron density by (0.55 ± 0.54) × 1012 cm-2. Hence, C60 induced a graphene Fermi energy downshift of about 100 meV, while Pentacene induced a Fermi energy upshift of about 120 meV. In both cases, the increase in charge carriers was accompanied by a reduced charge mobility, which resulted in a larger graphene sheet resistance of about 3 kΩ at the Dirac point. Interestingly, the contact resistance, which varied in the range 200 Ω-1 kΩ, was not significantly affected by the deposition of the organic molecules.
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Affiliation(s)
- Jacopo Oswald
- Empa, Swiss Federal Laboratories for Materials Science and Technology, Transport at Nanoscale Interfaces Laboratory, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland
- Swiss Nanoscience Institute, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Davide Beretta
- Empa, Swiss Federal Laboratories for Materials Science and Technology, Transport at Nanoscale Interfaces Laboratory, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland
| | - Michael Stiefel
- Empa, Swiss Federal Laboratories for Materials Science and Technology, Transport at Nanoscale Interfaces Laboratory, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland
| | - Roman Furrer
- Empa, Swiss Federal Laboratories for Materials Science and Technology, Transport at Nanoscale Interfaces Laboratory, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland
| | - Dominique Vuillaume
- Centre National de la Recherche Scientifique, Institute for Electronic, Microelectronic and Nanotechnology (IEMN), 59652 Villeneuve d’Ascq, France
| | - Michel Calame
- Empa, Swiss Federal Laboratories for Materials Science and Technology, Transport at Nanoscale Interfaces Laboratory, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland
- Swiss Nanoscience Institute, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
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