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Weber ML, Šmíd B, Breuer U, Rose MA, Menzler NH, Dittmann R, Waser R, Guillon O, Gunkel F, Lenser C. Space charge governs the kinetics of metal exsolution. NATURE MATERIALS 2024; 23:406-413. [PMID: 38168807 PMCID: PMC10917682 DOI: 10.1038/s41563-023-01743-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 10/30/2023] [Indexed: 01/05/2024]
Abstract
Nanostructured composite electrode materials play a major role in the fields of catalysis and electrochemistry. The self-assembly of metallic nanoparticles on oxide supports via metal exsolution relies on the transport of reducible dopants towards the perovskite surface to provide accessible catalytic centres at the solid-gas interface. At surfaces and interfaces, however, strong electrostatic gradients and space charges typically control the properties of oxides. Here we reveal that the nature of the surface-dopant interaction is the main determining factor for the exsolution kinetics of nickel in SrTi0.9Nb0.05Ni0.05O3-δ. The electrostatic interaction of dopants with surface space charge regions forming upon thermal oxidation results in strong surface passivation, which manifests in a retarded exsolution response. We furthermore demonstrate the controllability of the exsolution response via engineering of the perovskite surface chemistry. Our findings indicate that tailoring the electrostatic gradients at the perovskite surface is an essential step to improve exsolution-type materials in catalytic converters.
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Affiliation(s)
- Moritz L Weber
- Peter Gruenberg Institute - Electronic Materials (PGI-7), Forschungszentrum Juelich GmbH, Juelich, Germany.
- Institute of Energy and Climate Research - Materials Synthesis and Processing (IEK-1), Forschungszentrum Juelich GmbH, Juelich, Germany.
- Juelich-Aachen Research Alliance (JARA-FIT), Juelich, Germany.
- Institute of Mineral Engineering (GHI), RWTH Aachen University, Aachen, Germany.
| | - Břetislav Šmíd
- Department of Surface and Plasma Science, Charles University, Prague, Czech Republic
| | - Uwe Breuer
- Central Institute for Engineering, Electronics and Analytics (ZEA-3), Forschungszentrum Juelich GmbH, Juelich, Germany
| | - Marc-André Rose
- Peter Gruenberg Institute - Electronic Materials (PGI-7), Forschungszentrum Juelich GmbH, Juelich, Germany
- Juelich-Aachen Research Alliance (JARA-FIT), Juelich, Germany
- Institute for Electronic Materials (IWE 2), RWTH Aachen University, Aachen, Germany
| | - Norbert H Menzler
- Institute of Energy and Climate Research - Materials Synthesis and Processing (IEK-1), Forschungszentrum Juelich GmbH, Juelich, Germany
- Institute of Mineral Engineering (GHI), RWTH Aachen University, Aachen, Germany
| | - Regina Dittmann
- Peter Gruenberg Institute - Electronic Materials (PGI-7), Forschungszentrum Juelich GmbH, Juelich, Germany
- Juelich-Aachen Research Alliance (JARA-FIT), Juelich, Germany
| | - Rainer Waser
- Peter Gruenberg Institute - Electronic Materials (PGI-7), Forschungszentrum Juelich GmbH, Juelich, Germany
- Juelich-Aachen Research Alliance (JARA-FIT), Juelich, Germany
- Institute for Electronic Materials (IWE 2), RWTH Aachen University, Aachen, Germany
| | - Olivier Guillon
- Institute of Energy and Climate Research - Materials Synthesis and Processing (IEK-1), Forschungszentrum Juelich GmbH, Juelich, Germany
- Institute of Mineral Engineering (GHI), RWTH Aachen University, Aachen, Germany
- Juelich-Aachen Research Alliance (JARA-Energy), Juelich, Germany
| | - Felix Gunkel
- Peter Gruenberg Institute - Electronic Materials (PGI-7), Forschungszentrum Juelich GmbH, Juelich, Germany.
- Juelich-Aachen Research Alliance (JARA-FIT), Juelich, Germany.
| | - Christian Lenser
- Institute of Energy and Climate Research - Materials Synthesis and Processing (IEK-1), Forschungszentrum Juelich GmbH, Juelich, Germany.
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Wrana D, Cieślik K, Belza W, Rodenbücher C, Szot K, Krok F. Kelvin probe force microscopy work function characterization of transition metal oxide crystals under ongoing reduction and oxidation. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2019; 10:1596-1607. [PMID: 31467822 PMCID: PMC6693395 DOI: 10.3762/bjnano.10.155] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Accepted: 07/09/2019] [Indexed: 06/10/2023]
Abstract
Controlling the work function of transition metal oxides is of key importance with regard to future energy production and storage. As the majority of applications involve the use of heterostructures, the most suitable characterization technique is Kelvin probe force microscopy (KPFM), which provides excellent energetic and lateral resolution. In this paper, we demonstrate precise characterization of the work function using the example of artificially formed crystalline titanium monoxide (TiO) nanowires on strontium titanate (SrTiO3) surfaces, providing a sharp atomic interface. The measured value of 3.31(21) eV is the first experimental work function evidence for a cubic TiO phase, where significant variations among the different crystallographic facets were also observed. Despite the remarkable height of the TiO nanowires, KPFM was implemented to achieve a high lateral resolution of 15 nm, which is close to the topographical limit. In this study, we also show the unique possibility of obtaining work function and conductivity maps on the same area by combining noncontact and contact modes of atomic force microscopy (AFM). As most of the real applications require ambient operating conditions, we have additionally checked the impact of air venting on the work function of the TiO/SrTiO3(100) heterostructure, proving that surface reoxidation occurs and results in a work function increase of 0.9 eV and 0.6 eV for SrTiO3 and TiO, respectively. Additionally, the influence of adsorbed surface species was estimated to contribute 0.4 eV and 0.2 eV to the work function of both structures. The presented method employing KPFM and local conductivity AFM for the characterization of the work function of transition metal oxides may help in understanding the impact of reduction and oxidation on electronic properties, which is of high importance in the development of effective sensing and catalytic devices.
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Affiliation(s)
- Dominik Wrana
- Marian Smoluchowski Institute of Physics, Jagiellonian University, Lojasiewicza 11, 30-348 Krakow, Poland
| | - Karol Cieślik
- Marian Smoluchowski Institute of Physics, Jagiellonian University, Lojasiewicza 11, 30-348 Krakow, Poland
| | - Wojciech Belza
- Marian Smoluchowski Institute of Physics, Jagiellonian University, Lojasiewicza 11, 30-348 Krakow, Poland
| | - Christian Rodenbücher
- Institute of Energy and Climate Research (IEK-3), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Krzysztof Szot
- Peter Grünberg Institute (PGI-7), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
- August Chelkowski Institute of Physics, University of Silesia, 40–007 Katowice, Poland
| | - Franciszek Krok
- Marian Smoluchowski Institute of Physics, Jagiellonian University, Lojasiewicza 11, 30-348 Krakow, Poland
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Mathieu C, Gonzalez S, Lubin C, Copie O, Feyer V, Schneider CM, Barrett N. High-temperature 2D Fermi surface of SrTiO3
studied by energy-filtered PEEM. SURF INTERFACE ANAL 2018. [DOI: 10.1002/sia.6533] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Claire Mathieu
- SPEC, CEA, CNRS; Université Paris-Saclay, CEA Saclay; Gif-sur-Yvette Cedex France
| | - Sara Gonzalez
- SPEC, CEA, CNRS; Université Paris-Saclay, CEA Saclay; Gif-sur-Yvette Cedex France
- BaDElPh beamline; Elettra-Sincrotrone Trieste; S.S. 14 km 163.5 in AREA Science Park Basovizza I-34149 Trieste Italy
| | - Christophe Lubin
- SPEC, CEA, CNRS; Université Paris-Saclay, CEA Saclay; Gif-sur-Yvette Cedex France
| | - Olivier Copie
- Institut Jean Lamour; UMR 7198 CNRS/Université de Lorraine; Vandoeuvre-lès-Nancy France
| | - Vitaliy Feyer
- Peter Grünberg Institute (PGI-6); JARA-FIT, Research Center Jülich; Jülich Germany
- NanoESCA beamline; Elettra-Sincrotrone Trieste; S.S. 14 km 163.5 in AREA Science Park Basovizza I-34149 Trieste Italy
| | - Claus M. Schneider
- Peter Grünberg Institute (PGI-6); JARA-FIT, Research Center Jülich; Jülich Germany
| | - Nick Barrett
- SPEC, CEA, CNRS; Université Paris-Saclay, CEA Saclay; Gif-sur-Yvette Cedex France
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Baeumer C, Schmitz C, Ramadan AHH, Du H, Skaja K, Feyer V, Müller P, Arndt B, Jia CL, Mayer J, De Souza RA, Michael Schneider C, Waser R, Dittmann R. Spectromicroscopic insights for rational design of redox-based memristive devices. Nat Commun 2015; 6:8610. [PMID: 26477940 PMCID: PMC4634325 DOI: 10.1038/ncomms9610] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 09/10/2015] [Indexed: 11/23/2022] Open
Abstract
The demand for highly scalable, low-power devices for data storage and logic operations is strongly stimulating research into resistive switching as a novel concept for future non-volatile memory devices. To meet technological requirements, it is imperative to have a set of material design rules based on fundamental material physics, but deriving such rules is proving challenging. Here, we elucidate both switching mechanism and failure mechanism in the valence-change model material SrTiO3, and on this basis we derive a design rule for failure-resistant devices. Spectromicroscopy reveals that the resistance change during device operation and failure is indeed caused by nanoscale oxygen migration resulting in localized valence changes between Ti(4+) and Ti(3+). While fast reoxidation typically results in retention failure in SrTiO3, local phase separation within the switching filament stabilizes the retention. Mimicking this phase separation by intentionally introducing retention-stabilization layers with slow oxygen transport improves retention times considerably.
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Affiliation(s)
- Christoph Baeumer
- Peter Gruenberg Institute, Forschungszentrum Juelich GmbH and JARA-FIT, 52425 Juelich, Germany
| | - Christoph Schmitz
- Peter Gruenberg Institute, Forschungszentrum Juelich GmbH and JARA-FIT, 52425 Juelich, Germany
| | - Amr H. H. Ramadan
- Institute of Physical Chemistry, RWTH Aachen University and JARA-FIT, 52056 Aachen, Germany
| | - Hongchu Du
- Peter Gruenberg Institute, Forschungszentrum Juelich GmbH and JARA-FIT, 52425 Juelich, Germany
- Ernst Ruska-Centre, Forschungszentrum Juelich GmbH and RWTH Aachen University, 52425 Juelich, Germany
| | - Katharina Skaja
- Peter Gruenberg Institute, Forschungszentrum Juelich GmbH and JARA-FIT, 52425 Juelich, Germany
| | - Vitaliy Feyer
- Peter Gruenberg Institute, Forschungszentrum Juelich GmbH and JARA-FIT, 52425 Juelich, Germany
| | - Philipp Müller
- Peter Gruenberg Institute, Forschungszentrum Juelich GmbH and JARA-FIT, 52425 Juelich, Germany
| | - Benedikt Arndt
- Peter Gruenberg Institute, Forschungszentrum Juelich GmbH and JARA-FIT, 52425 Juelich, Germany
| | - Chun-Lin Jia
- Peter Gruenberg Institute, Forschungszentrum Juelich GmbH and JARA-FIT, 52425 Juelich, Germany
- Ernst Ruska-Centre, Forschungszentrum Juelich GmbH and RWTH Aachen University, 52425 Juelich, Germany
| | - Joachim Mayer
- Peter Gruenberg Institute, Forschungszentrum Juelich GmbH and JARA-FIT, 52425 Juelich, Germany
- Ernst Ruska-Centre, Forschungszentrum Juelich GmbH and RWTH Aachen University, 52425 Juelich, Germany
| | - Roger A. De Souza
- Institute of Physical Chemistry, RWTH Aachen University and JARA-FIT, 52056 Aachen, Germany
| | - Claus Michael Schneider
- Peter Gruenberg Institute, Forschungszentrum Juelich GmbH and JARA-FIT, 52425 Juelich, Germany
| | - Rainer Waser
- Peter Gruenberg Institute, Forschungszentrum Juelich GmbH and JARA-FIT, 52425 Juelich, Germany
- Institute of Materials in Electrical Engineering and Information Technology II, RWTH Aachen University, 52056 Aachen, Germany
| | - Regina Dittmann
- Peter Gruenberg Institute, Forschungszentrum Juelich GmbH and JARA-FIT, 52425 Juelich, Germany
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Ifland B, Peretzki P, Kressdorf B, Saring P, Kelling A, Seibt M, Jooss C. Current-voltage characteristics of manganite-titanite perovskite junctions. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2015; 6:1467-84. [PMID: 26199851 PMCID: PMC4505172 DOI: 10.3762/bjnano.6.152] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 06/16/2015] [Indexed: 06/05/2023]
Abstract
After a general introduction into the Shockley theory of current voltage (J-V) characteristics of inorganic and organic semiconductor junctions of different bandwidth, we apply the Shockley theory-based, one diode model to a new type of perovskite junctions with polaronic charge carriers. In particular, we studied manganite-titanate p-n heterojunctions made of n-doped SrTi1- y Nb y O3, y = 0.002 and p-doped Pr1- x Ca x MnO3, x = 0.34 having a strongly correlated electron system. The diffusion length of the polaron carriers was analyzed by electron beam-induced current (EBIC) in a thin cross plane lamella of the junction. In the J-V characteristics, the polaronic nature of the charge carriers is exhibited mainly by the temperature dependence of the microscopic parameters, such as the hopping mobility of the series resistance and a colossal electro-resistance (CER) effect in the parallel resistance. We conclude that a modification of the Shockley equation incorporating voltage-dependent microscopic polaron parameters is required. Specifically, the voltage dependence of the reverse saturation current density is analyzed and interpreted as a voltage-dependent electron-polaron hole-polaron pair generation and separation at the interface.
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Affiliation(s)
- Benedikt Ifland
- Institute of Materials Physics, University of Goettingen, Friedrich-Hund-Platz 1, 37077 Goettingen, Germany
| | - Patrick Peretzki
- 4th Physical Institute, University of Goettingen, Friedrich-Hund-Platz 1, 37077 Goettingen, Germany
| | - Birte Kressdorf
- Institute of Materials Physics, University of Goettingen, Friedrich-Hund-Platz 1, 37077 Goettingen, Germany
| | - Philipp Saring
- 4th Physical Institute, University of Goettingen, Friedrich-Hund-Platz 1, 37077 Goettingen, Germany
| | - Andreas Kelling
- Institute of Materials Physics, University of Goettingen, Friedrich-Hund-Platz 1, 37077 Goettingen, Germany
| | - Michael Seibt
- 4th Physical Institute, University of Goettingen, Friedrich-Hund-Platz 1, 37077 Goettingen, Germany
| | - Christian Jooss
- Institute of Materials Physics, University of Goettingen, Friedrich-Hund-Platz 1, 37077 Goettingen, Germany
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6
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Mottaghizadeh A, Yu Q, Lang PL, Zimmers A, Aubin H. Metal oxide resistive switching: evolution of the density of states across the metal-insulator transition. PHYSICAL REVIEW LETTERS 2014; 112:066803. [PMID: 24580702 DOI: 10.1103/physrevlett.112.066803] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Indexed: 06/03/2023]
Abstract
We report the study of gold-SrTiO3 (STO)-gold memristors where the doping concentration in STO can be fine-tuned through electric field migration of oxygen vacancies. In this tunnel junction device, the evolution of the density of states (DOS) can be followed continuously across the metal-insulator transition (MIT). At very low dopant concentration, the junction displays characteristic signatures of discrete dopant levels. As the dopant concentration increases, the semiconductor band gap fills in but a soft Coulomb gap remains. At even higher doping, a transition to a metallic state occurs where the DOS at the Fermi level becomes finite and Altshuler-Aronov corrections to the DOS are observed. At the critical point of the MIT, the DOS scales linearly with energy N(ϵ)∼ϵ, the possible signature of multifractality.
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Affiliation(s)
- A Mottaghizadeh
- Laboratoire de Physique et d'Etude des Matériaux, UMR 8213, ESPCI-ParisTech-CNRS-UPMC, 10 rue Vauquelin, 75231 Paris, France
| | - Q Yu
- Laboratoire de Physique et d'Etude des Matériaux, UMR 8213, ESPCI-ParisTech-CNRS-UPMC, 10 rue Vauquelin, 75231 Paris, France
| | - P L Lang
- Laboratoire de Physique et d'Etude des Matériaux, UMR 8213, ESPCI-ParisTech-CNRS-UPMC, 10 rue Vauquelin, 75231 Paris, France
| | - A Zimmers
- Laboratoire de Physique et d'Etude des Matériaux, UMR 8213, ESPCI-ParisTech-CNRS-UPMC, 10 rue Vauquelin, 75231 Paris, France
| | - H Aubin
- Laboratoire de Physique et d'Etude des Matériaux, UMR 8213, ESPCI-ParisTech-CNRS-UPMC, 10 rue Vauquelin, 75231 Paris, France
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7
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Bußmann BK, Marinov K, Ochedowski O, Scheuschner N, Maultzsch J, Schleberger M. Electronic characterization of single-layer MoS2 sheets exfoliated on SrTiO3. ACTA ACUST UNITED AC 2012. [DOI: 10.1557/opl.2012.1463] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
ABSTRACTSingle layer regions of MoS2 on SiO2 and SrTiO3 were identified by Raman spectroscopy and μ-photoluminescence before Kelvin probe force microscopy was performed. For the already known system MoS2/SiO2 we find 1.839 eV for the direct bandgap, in good agreement with earlier results. On MoS2/SrTiO3 the direct bandgap was determined to be 1.829 eV. From our Kelvin probe data we infer that the SrTiO3 substrate leads to a dipole layer at the interface of the MoS2 single layer. The corresponding μ-PL measurements however show no significant decrease of the bandgap. This shows, that in the case of MoS2 the carrier type as well as concentration is not significantly influenced by the choice of SrTiO3 as the substrate compared to SiO2.
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Bussmann BK, Ochedowski O, Schleberger M. Doping of graphene exfoliated on SrTiO3. NANOTECHNOLOGY 2011; 22:265703. [PMID: 21576809 DOI: 10.1088/0957-4484/22/26/265703] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We present atomic force microscopy and scanning Kelvin probe data obtained under ultra-high vacuum conditions from graphene exfoliated on crystalline SrTiO(3) substrates. The contact potential difference shows a monotonic increase with the number of graphene layers until after five layers of saturation is reached. By identifying the saturation value with the work function of graphite we determine the work function of single and bilayer graphene to be Φ(SLG) = 4.409 ± 0.039 eV and Φ(BLG) = 4.516 ± 0.035 eV, respectively. In agreement with the higher work function of single-layer graphene with respect to free-standing graphene, our measurements indicate an accumulation of charge carriers corresponding to a doping of the exfoliated graphene layer with electrons.
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