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Gnoli L, Benini M, Del Conte C, Riminucci A, Rakshit RK, Singh M, Sanna S, Yadav R, Lin KW, Mezzi A, Achilli S, Molteni E, Marino M, Fratesi G, Dediu V, Bergenti I. Enhancement of Magnetic Stability in Antiferromagnetic CoO Films by Adsorption of Organic Molecules. ACS APPLIED ELECTRONIC MATERIALS 2024; 6:3138-3146. [PMID: 38828040 PMCID: PMC11137817 DOI: 10.1021/acsaelm.3c01599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Revised: 02/14/2024] [Accepted: 02/19/2024] [Indexed: 06/05/2024]
Abstract
Antiferromagnets are a class of magnetic materials of great interest in spintronic devices because of their stability and ultrafast dynamics. When interfaced with an organic molecular layer, antiferromagnetic (AF) films are expected to form a spinterface that can allow fine control of specific AF properties. In this paper, we investigate spinterface effects on CoO, an AF oxide. To access the magnetic state of the antiferromagnet, we couple it to a ferromagnetic Co film via an exchange bias (EB) effect. In this way, the formation of a spinterface is detected through changes induced on the CoO/Co EB system. We demonstrate that C60 and Gaq3 adsorption on CoO shifts its blocking temperature; in turn, an increase in both the EB fields and the coercivities is observed on the EB-coupled Co layer. Ab initio calculations for the CoO/C60 interface indicate that the molecular adsorption is responsible for a charge redistribution on the CoO layer that alters the occupation of the d orbitals of Co atoms and, to a smaller extent, the p orbitals of oxygen. As a result, the AF coupling between Co atoms in the CoO is enhanced. Considering the granular nature of CoO, a larger AF stability upon molecular adsorption is then associated with a larger number of AF grains that are stable upon reversal of the Co layer.
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Affiliation(s)
- Luca Gnoli
- CNR
ISMN, Via Gobetti 101, 40129 Bologna, Italy
| | | | - Corrado Del Conte
- Department
of Physics and Astronomy “A. Righi”, University of Bologna, Via Berti-Pichat 6/2, I-40127 Bologna, Italy
| | | | | | - Manju Singh
- CNR
ISMN, Via Gobetti 101, 40129 Bologna, Italy
| | - Samuele Sanna
- Department
of Physics and Astronomy “A. Righi”, University of Bologna, Via Berti-Pichat 6/2, I-40127 Bologna, Italy
| | - Roshni Yadav
- Materials
Science and Engineering Department, National
Chung Hsing University, Taichung 402, Taiwan
| | - Ko-Wei Lin
- Materials
Science and Engineering Department, National
Chung Hsing University, Taichung 402, Taiwan
| | - Alessio Mezzi
- CNR
ISMN, Via Salaria km
29.300, 00015 Monterotondo
Scalo, Italy
| | - Simona Achilli
- Physics
Department, Università degli Studi
di Milano, Via Celoria 16, 20133 Milan, Italy
| | - Elena Molteni
- Physics
Department, Università degli Studi
di Milano, Via Celoria 16, 20133 Milan, Italy
| | - Marco Marino
- Physics
Department, Università degli Studi
di Milano, Via Celoria 16, 20133 Milan, Italy
| | - Guido Fratesi
- Physics
Department, Università degli Studi
di Milano, Via Celoria 16, 20133 Milan, Italy
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2
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Albani G, Capra M, Lodesani A, Calloni A, Bussetti G, Finazzi M, Ciccacci F, Brambilla A, Duò L, Picone A. Self-assembly of C 60 on a ZnTPP/Fe(001)- p(1 × 1)O substrate: observation of a quasi-freestanding C 60 monolayer. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2022; 13:857-864. [PMID: 36105692 PMCID: PMC9443418 DOI: 10.3762/bjnano.13.76] [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: 04/29/2022] [Accepted: 08/11/2022] [Indexed: 06/15/2023]
Abstract
Fullerene (C60) has been deposited in ultrahigh vacuum on top of a zinc tetraphenylporphyrin (ZnTPP) monolayer self-assembled on a Fe(001)-p(1 × 1)O substrate. The nanoscale morphology and the electronic properties of the C60/ZnTPP/Fe(001)-p(1 × 1)O heterostructure have been investigated by scanning tunneling microscopy/spectroscopy and ultraviolet photoemission spectroscopy. C60 nucleates compact and well-ordered hexagonal domains on top of the ZnTPP buffer layer, suggesting a high surface diffusivity of C60 and a weak coupling between the overlayer and the substrate. Accordingly, work function measurements reveal a negligible charge transfer at the C60/ZnTPP interface. Finally, the difference between the energy of the lowest unoccupied molecular orbital (LUMO) and that of the highest occupied molecular orbital (HOMO) measured on C60 is about 3.75 eV, a value remarkably higher than those found in fullerene films stabilized directly on metal surfaces. Our results unveil a model system that could be useful in applications in which a quasi-freestanding monolayer of C60 interfaced with a metallic electrode is required.
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Affiliation(s)
- Guglielmo Albani
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Michele Capra
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Alessandro Lodesani
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Alberto Calloni
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Gianlorenzo Bussetti
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Marco Finazzi
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Franco Ciccacci
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Alberto Brambilla
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Lamberto Duò
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Andrea Picone
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
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Picone A, Finazzi M, Duò L, Giannotti D, Ciccacci F, Brambilla A. Observation of a Metastable Honeycomb Arrangement of C 60 on Ni(111) with (7 × 7) Periodicity: Tailoring an Interface for Organic Spintronics. ACS APPLIED NANO MATERIALS 2021; 4:12993-13000. [PMID: 34977478 PMCID: PMC8713361 DOI: 10.1021/acsanm.1c02060] [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: 07/20/2021] [Accepted: 11/23/2021] [Indexed: 06/14/2023]
Abstract
Hybrid nanostructures in which organic molecules are interfaced with metal surfaces hold promise for the discovery of intriguing physical and chemical phenomena, as well as for the development of innovative devices. In this frame, it is crucial to understand the interplay between the structural details of the interface and the electronic properties of the system. Here, an experimental investigation of the C60/Ni(111) interface is performed by means of scanning tunneling microscopy/spectroscopy (STM/STS) and low-energy electron diffraction (LEED). The deposition of C60 at room temperature, followed by high-temperature annealing, promotes the stabilization of two different phases. A hitherto unreported phase forming a (7 × 7) honeycomb overlayer coexists with the well-known (4 × 4) reconstruction. Highly resolved STM images disclose the adsorption geometry of the molecules for both phases. STS reveals that the electronic properties of C60/Ni(111) are strongly influenced by the morphology of the interface, suggesting the possibility of tuning the electronic properties of the organic/inorganic heterostructures by adjusting the structural coupling with the substrate. This achievement can be important for hybrid magnetic interfaces, where the harmonization between the molecular and the magnetic orders can enhance the development of hybrid magnetic states.
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Orlando F, Fratesi G, Onida G, Achilli S. Tailoring the magnetic ordering of the Cr 4O 5/Fe(001) surface via a controlled adsorption of C 60 organic molecules. Phys Chem Chem Phys 2021; 23:7948-7954. [PMID: 33439166 DOI: 10.1039/d0cp05848c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We analyse the spinterface formed by a C60 molecular layer on a Fe(001) surface covered by a two-dimensional Cr4O5 layer. We consider different geometries, by combining the high symmetry adsorption sites of the surface with three possible orientations of the molecules in a fully relaxed Density Functional Theory calculation. We show that the local hybridization between the electronic states of the Cr4O5 layer and those of the organic molecules is able to modify the magnetic coupling of the Cr atoms. Both the intra-layer and the inter-layer magnetic interaction is indeed driven by O atoms of the two-dimensional oxide. We demonstrate that the C60 adsorption on the energetically most stable site turns the ferromagnetic intra-layer coupling into an antiferromagnetic one, and that antiferromagnetic to ferromagnetic switching and spin patterning of the substrate could be possible by adsorption on other sites.
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Affiliation(s)
- Federico Orlando
- Dipartimento di Fisica "Aldo Pontremoli", Università degli Studi di Milano, Via Celoria 16, I-20133 Milano, Italy
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An In-Depth Assessment of the Electronic and Magnetic Properties of a Highly Ordered Hybrid Interface: The Case of Nickel Tetra-Phenyl-Porphyrins on Fe(001)- p(1 × 1)O. MICROMACHINES 2021; 12:mi12020191. [PMID: 33668500 PMCID: PMC7918924 DOI: 10.3390/mi12020191] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Revised: 02/08/2021] [Accepted: 02/11/2021] [Indexed: 11/17/2022]
Abstract
In this paper we focus on the structural, electronic, and magnetic properties of Ni tetra-phenyl-porphyrins (NiTPP) grown on top of Fe(001)–p(1 × 1)O. Ordered thin films of metal TPP molecules are potentially interesting for organic electronic and spintronic applications, especially when they are coupled to a ferromagnetic substrate. Unfortunately, porphyrin layers deposited on top of ferromagnetic substrates do not generally show long-range order. In this work, we provide evidence of an ordered disposition of the organic film above the iron surface and we prove that the thin layer of iron oxide decouples the molecules from the substrate, thus preserving the molecular electronic features, especially the HOMO-LUMO gap, even when just a few organic layers are deposited. The effect of the exposure to molecular oxygen is also investigated and an increased robustness against oxidation with respect to the bare substrate is detected. Finally, we present our results for the magnetic analysis performed by spin resolved spectroscopy, finding a null magnetic coupling between the molecules and the substrate.
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Rabia A, Tumino F, Milani A, Russo V, Bassi AL, Bassi N, Lucotti A, Achilli S, Fratesi G, Manini N, Onida G, Sun Q, Xu W, Casari CS. Structural, Electronic, and Vibrational Properties of a Two-Dimensional Graphdiyne-like Carbon Nanonetwork Synthesized on Au(111): Implications for the Engineering of sp-sp 2 Carbon Nanostructures. ACS APPLIED NANO MATERIALS 2020; 3:12178-12187. [PMID: 33392466 PMCID: PMC7771048 DOI: 10.1021/acsanm.0c02665] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2020] [Accepted: 11/19/2020] [Indexed: 05/08/2023]
Abstract
Graphdiyne, atomically thin two-dimensional (2D) carbon nanostructure based on sp-sp2 hybridization is an appealing system potentially showing outstanding mechanical and optoelectronic properties. Surface-catalyzed coupling of halogenated sp-carbon-based molecular precursors represents a promising bottom-up strategy to fabricate extended 2D carbon systems with engineered structure on metallic substrates. Here, we investigate the atomic-scale structure and electronic and vibrational properties of an extended graphdiyne-like sp-sp2 carbon nanonetwork grown on Au(111) by means of the on-surface synthesis. The formation of such a 2D nanonetwork at its different stages as a function of the annealing temperature after the deposition is monitored by scanning tunneling microscopy (STM), Raman spectroscopy, and combined with density functional theory (DFT) calculations. High-resolution STM imaging and the high sensitivity of Raman spectroscopy to the bond nature provide a unique strategy to unravel the atomic-scale properties of sp-sp2 carbon nanostructures. We show that hybridization between the 2D carbon nanonetwork and the underlying substrate states strongly affects its electronic and vibrational properties, modifying substantially the density of states and the Raman spectrum compared to the free standing system. This opens the way to the modulation of the electronic properties with significant prospects in future applications as active nanomaterials for catalysis, photoconversion, and carbon-based nanoelectronics.
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Affiliation(s)
- Andi Rabia
- Department
of Energy, Politecnico di Milano via Ponzio 34/3, Milano I-20133, Italy
| | - Francesco Tumino
- Department
of Energy, Politecnico di Milano via Ponzio 34/3, Milano I-20133, Italy
| | - Alberto Milani
- Department
of Energy, Politecnico di Milano via Ponzio 34/3, Milano I-20133, Italy
| | - Valeria Russo
- Department
of Energy, Politecnico di Milano via Ponzio 34/3, Milano I-20133, Italy
| | - Andrea Li Bassi
- Department
of Energy, Politecnico di Milano via Ponzio 34/3, Milano I-20133, Italy
| | - Nicolò Bassi
- Department
of Energy, Politecnico di Milano via Ponzio 34/3, Milano I-20133, Italy
| | - Andrea Lucotti
- Dipartimento
di Chimica, Materiali e Ingegneria Chimica “G. Natta”, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano 20133, Italy
| | - Simona Achilli
- ETSF
and Dipartimento di Fisica “Aldo Pontremoli”, Università degli Studi di Milano, Via Celoria, 16, Milano I-20133, Italy
| | - Guido Fratesi
- ETSF
and Dipartimento di Fisica “Aldo Pontremoli”, Università degli Studi di Milano, Via Celoria, 16, Milano I-20133, Italy
| | - Nicola Manini
- ETSF
and Dipartimento di Fisica “Aldo Pontremoli”, Università degli Studi di Milano, Via Celoria, 16, Milano I-20133, Italy
| | - Giovanni Onida
- ETSF
and Dipartimento di Fisica “Aldo Pontremoli”, Università degli Studi di Milano, Via Celoria, 16, Milano I-20133, Italy
| | - Qiang Sun
- Interdisciplinary
Materials Research Center, College of Materials Science and Engineering, Tongji University, Shanghai 201804, P. R. China
| | - Wei Xu
- Interdisciplinary
Materials Research Center, College of Materials Science and Engineering, Tongji University, Shanghai 201804, P. R. China
| | - Carlo S. Casari
- Department
of Energy, Politecnico di Milano via Ponzio 34/3, Milano I-20133, Italy
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8
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Li D, Wang X, Lin Z, Zheng Y, Jiang Q, Zheng N, Zhang W, Jin KJ, Yu G. Tuning Charge Carrier and Spin Transport Properties via Structural Modification of Polymer Semiconductors. ACS APPLIED MATERIALS & INTERFACES 2019; 11:30089-30097. [PMID: 31342737 DOI: 10.1021/acsami.9b07863] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Targeted design of organic semiconductors in organic spintronics is relatively limited. Therefore, four conjugated polymers with analogous structures based on isoindigo (IID) units were designed and synthesized to investigate the structure-property relationships in spin and charge carrier transport. Structural design strategies include introduction of pyridinic nitrogen atoms into IID units to change electronic structures and alteration of different branching points of alkyl chains to adjust the aggregation structure. By fabricating polymer field-effect transistors (PFETs) and organic spin valves (OSVs), all of the polymers exhibited good ambipolar field-effect properties (all of the mobilities exceeding 0.3 cm2 V-1 s-1) and relatively high magnetoresistance (MR) values (maximum up to 25%). Most importantly, it is found that the introduction of pyridinic nitrogen into the IID units can improve MR values of OSVs and electron mobilities of PFETs, whereas the extension of alkyl chain branching points can reduce MR values of the conjugated polymers. This work is the first attempt to thoroughly study the structure-property relationship in the OSVs, combined with molecular design of the conjugated polymers, which provides a guideline for molecular engineering, especially for organic spintronics.
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Affiliation(s)
- Dong Li
- Beijing National Laboratory for Molecular Sciences, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry , Chinese Academy of Sciences , Beijing 100190 , P. R. China
- University of Chinese Academy of Sciences , Beijing 100049 , P. R. China
| | - Xiang Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics , Chinese Academy of Sciences , Beijing 100190 , P. R. China
- University of Chinese Academy of Sciences , Beijing 100049 , P. R. China
- Songshan Lake Materials Laboratory , Dongguan , Guangdong 523808 , P. R. China
| | - Zuzhang Lin
- Beijing National Laboratory for Molecular Sciences, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry , Chinese Academy of Sciences , Beijing 100190 , P. R. China
| | - Yuanhui Zheng
- Beijing National Laboratory for Molecular Sciences, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry , Chinese Academy of Sciences , Beijing 100190 , P. R. China
| | - Qianqing Jiang
- Beijing National Laboratory for Molecular Sciences, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry , Chinese Academy of Sciences , Beijing 100190 , P. R. China
| | - Naihang Zheng
- Beijing National Laboratory for Molecular Sciences, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry , Chinese Academy of Sciences , Beijing 100190 , P. R. China
- University of Chinese Academy of Sciences , Beijing 100049 , P. R. China
| | - Weifeng Zhang
- Beijing National Laboratory for Molecular Sciences, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry , Chinese Academy of Sciences , Beijing 100190 , P. R. China
| | - Kui-Juan Jin
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics , Chinese Academy of Sciences , Beijing 100190 , P. R. China
- University of Chinese Academy of Sciences , Beijing 100049 , P. R. China
- Songshan Lake Materials Laboratory , Dongguan , Guangdong 523808 , P. R. China
| | - Gui Yu
- Beijing National Laboratory for Molecular Sciences, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry , Chinese Academy of Sciences , Beijing 100190 , P. R. China
- University of Chinese Academy of Sciences , Beijing 100049 , P. R. China
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