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Yan X, Wrobel F, Tung IC, Zhou H, Hong H, Rodolakis F, Bhattacharya A, McChesney JL, Fong DD. Origin of the 2D Electron Gas at the SrTiO 3 Surface. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2200866. [PMID: 35429184 DOI: 10.1002/adma.202200866] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 04/04/2022] [Indexed: 06/14/2023]
Abstract
Bulk SrTiO3 is a well-known band insulator and the most common substrate used in the field of complex oxide heterostructures. Its surface and interface with other oxides, however, have demonstrated a variety of remarkable behaviors distinct from those expected. In this work, using a suite of in situ techniques to monitor both the atomic and electronic structures of the SrTiO3 (001) surface prior to and during growth, the disappearance and re-appearance of a 2D electron gas (2DEG) is observed after the completion of each SrO and TiO2 monolayer, respectively. The 2DEG is identified with the TiO2 double layer present at the initial SrTiO3 surface, which gives rise to a surface potential and mobile electrons due to vacancies within the TiO2-x adlayer. Much like the electronic reconstruction discovered in other systems, two atomic planes are required, here supplied by the double layer. The combined in situ scattering/spectroscopy findings resolve a number of longstanding issues associated with complex oxide interfaces, facilitating the employment of atomic-scale defect engineering in oxide electronics.
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Affiliation(s)
- Xi Yan
- Materials Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Friederike Wrobel
- Materials Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - I-Cheng Tung
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Hua Zhou
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Hawoong Hong
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Fanny Rodolakis
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Anand Bhattacharya
- Materials Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Jessica L McChesney
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Dillon D Fong
- Materials Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
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Wan G, Sun CJ, Freeland JW, Fong DD. Defect-Driven Oxide Transformations and the Electrochemical Interphase. Acc Chem Res 2021; 54:3039-3049. [PMID: 34297550 DOI: 10.1021/acs.accounts.1c00248] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
ConspectusThe redox reaction pathway is crucial to the sustainable production of the fuels and chemicals required for a carbon-neutral society. Our society is becoming increasingly dependent on devices using batteries and electrolyzers, all of which rely on a series of redox reactions. The overall properties of oxide materials make them very well suited for such electrochemical and catalytic applications due to their associated cationic redox properties and the static site-adsorbate interactions. As these technologies have matured, it has become apparent that defect-driven redox reactions, defect-coupled diffusion, and structural transformations that are both time- and rate-dependent are also critical materials processes. This change in focus, considering not only redox properties but also more complex, dynamic behaviors, represents a new research frontier in the molecular sciences as they are strongly linked to device operation and degradation and lie at the heart of various phenomena that take place at electrochemical interfaces. Fundamental studies of the structural, electronic, and chemical transformation mechanisms are key to the advancement of materials and technological innovations that could be implemented in various electrochemical systems.In this Account, we focus on recent studies and advances in characterizing and understanding the dynamic redox evolution and structural transformations that take place in model perovskites and layered oxides under reactive conditions and correlate them with degradation mechanisms and operations in electrolyzers and batteries. We show that the dynamic evolution of oxygen vacancies and cationic migration in the surface or bulk occurs at the solid-liquid interface, using a combination of different synchrotron-based X-ray spectroscopies and scattering probes. Detailed redox-structure-reactivity correlation studies show how defects and diffusion processes can be tailored to drive various physical and chemical transformations in electrolyzers and batteries. We also highlight a strong correlation between oxygen redox reactivity and structural reorganization in both model thin films and particles, helping to bridge the gap between fundamental studies of the reaction mechanism and device applications. On the basis of these findings, we discuss strategies to probe and tune the redox reactivity and structural stability of the redox-active oxide interphase toward devising efficient pathways for energy and chemical harvesting.
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Ciatto G, Aubert N, Lecroard M, Engblom C, Fontaine P, Dubuisson JM, Abiven YM, Janolin PE, Kiat JM, Dumont Y, Berini B, Fouchet A, Keller N. FORTE - a multipurpose high-vacuum diffractometer for tender X-ray diffraction and spectroscopy at the SIRIUS beamline of Synchrotron SOLEIL. JOURNAL OF SYNCHROTRON RADIATION 2019; 26:1374-1387. [PMID: 31274467 DOI: 10.1107/s1600577519003722] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 03/18/2019] [Indexed: 06/09/2023]
Abstract
A new high-vacuum multipurpose diffractometer (called FORTE from the French acronyms of the project) has recently been installed at the tender/hard X-ray SIRIUS beamline of Synchrotron SOLEIL, France. The geometry chosen allows one to work either in the classical Eulerian four-circle geometry for bulk X-ray diffraction (XRD) or in the z-axis geometry for surface XRD. The diffractometer nicely fits the characteristics of the SIRIUS beamline, optimized to work in the 1.1-4.5 keV range, and allows one to perform unprecedented diffraction anomalous fine structure (DAFS) experiments in the tender X-ray region, also around non-specular reflections, covering a large reciprocal-space volume. Installation of an X-ray fluorescence detector on a dedicated flange allows simultaneous DAFS and X-ray absorption (XAS) measurements. The access to the tender X-ray region paves the way to resonant investigations around the L-edges of second-row transition elements which are constituents of functional oxide materials. It also enables access to several edges of interest for semiconductors. Finally, the control architecture based on synchronized Delta Tau units opens up exciting perspectives for improvement of the mechanical sphere of confusion.
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Affiliation(s)
- G Ciatto
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48 F-91192 Gif sur Yvette CEDEX, France
| | - N Aubert
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48 F-91192 Gif sur Yvette CEDEX, France
| | - M Lecroard
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48 F-91192 Gif sur Yvette CEDEX, France
| | - C Engblom
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48 F-91192 Gif sur Yvette CEDEX, France
| | - P Fontaine
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48 F-91192 Gif sur Yvette CEDEX, France
| | - J M Dubuisson
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48 F-91192 Gif sur Yvette CEDEX, France
| | - Y M Abiven
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48 F-91192 Gif sur Yvette CEDEX, France
| | - P E Janolin
- Laboratoire SPMS, UMR CNRS-CentraleSupélec, Bâtiment Gustave Eiffel - MB.105, 8-10 rue Joliot-Curie, 91190 Gif-Sur-Yvette CEDEX, France
| | - J M Kiat
- Laboratoire SPMS, UMR CNRS-CentraleSupélec, Bâtiment Gustave Eiffel - MB.105, 8-10 rue Joliot-Curie, 91190 Gif-Sur-Yvette CEDEX, France
| | - Y Dumont
- Groupe d'Etudes de la Matière Condensée (GEMaC), Université Versailles Saint-Quentin en Yvelines - CNRS, Université Paris-Saclay, Versailles, France
| | - B Berini
- Groupe d'Etudes de la Matière Condensée (GEMaC), Université Versailles Saint-Quentin en Yvelines - CNRS, Université Paris-Saclay, Versailles, France
| | - A Fouchet
- Groupe d'Etudes de la Matière Condensée (GEMaC), Université Versailles Saint-Quentin en Yvelines - CNRS, Université Paris-Saclay, Versailles, France
| | - N Keller
- Groupe d'Etudes de la Matière Condensée (GEMaC), Université Versailles Saint-Quentin en Yvelines - CNRS, Université Paris-Saclay, Versailles, France
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Cook S, Letchworth-Weaver K, Tung IC, Andersen TK, Hong H, Marks LD, Fong DD. How heteroepitaxy occurs on strontium titanate. SCIENCE ADVANCES 2019; 5:eaav0764. [PMID: 30993200 PMCID: PMC6461459 DOI: 10.1126/sciadv.aav0764] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2018] [Accepted: 02/14/2019] [Indexed: 06/01/2023]
Abstract
In traditional models of heteroepitaxy, the substrate serves mainly as a crystalline template for the thin-film lattice, dictating the initial roughness of the film and the degree of coherent strain. Here, performing in situ surface x-ray diffraction during the heteroepitaxial growth of LaTiO3 on SrTiO3 (001), we find that a TiO2 adlayer composed of the ( 13 × 13 ) R33.7° and ( 2 × 2 ) R45.0° reconstructions is a highly active participant in the growth process, continually diffusing to the surface throughout deposition. The effects of the TiO2 adlayer on layer-by-layer growth are investigated using different deposition sequences and anomalous x-ray scattering, both of which permit detailed insight into the dynamic layer rearrangements that take place. Our work challenges commonly held assumptions regarding growth on TiO2-terminated SrTiO3 (001) and demonstrates the critical role of excess TiO2 surface stoichiometry on the initial stages of heteroepitaxial growth on this important perovskite oxide substrate material.
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Affiliation(s)
- Seyoung Cook
- Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60202, USA
| | | | - I-Cheng Tung
- X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Tassie K. Andersen
- Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60202, USA
| | - Hawoong Hong
- X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Laurence D. Marks
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60202, USA
| | - Dillon D. Fong
- Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA
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Annese E, Dos Santos JE, Rodrigues GLMP, Rocha AS, de Moraes HR, Cezar JC. Ultrahigh-vacuum organic molecular-beam deposition system for in situ growth and characterization. JOURNAL OF SYNCHROTRON RADIATION 2018; 25:1658-1663. [PMID: 30407175 DOI: 10.1107/s1600577518011955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 08/23/2018] [Indexed: 06/08/2023]
Abstract
A compact ultrahigh-vacuum molecular-beam deposition system has been developed for the in situ synthesis of organic thin films and multilayers. The system incorporates all the features (heater, thickness monitor, evaporators) necessary for controlled organic thin-film growth. It can be used independently, or it can be docked to the in situ growth system and transferred to other instruments of the PGM beamline, thus allowing extensive film preparation and characterization. A manipulator dedicated to specimen preparation and organic-film deposition with temperature control between 200 K and ∼800 K has been developed. The design and performance of the system are reported with emphasis on a novel solution of masks developed to achieve position-dependent film deposition. To demonstrate the enhanced capabilities of the PGM beamline in the growth and in the characterization of electronic-structure studies of organic molecular films and their heterostructures through synchrotron-based spectroscopies, this paper presents some preliminary results of a study of Fe-phthalocyanine growth on Si substrates and on in situ prepared La0.67Sr0.33MnO3 buffer layers on SrTiO3 single crystal.
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Affiliation(s)
- Emilia Annese
- Laboratório Nacional de Luz Síncrotron - Centro Nacional de Pesquisa em Energia e Materiais - CP 6192, 13083-970 Campinas, SP, Brazil
| | - Joacir E Dos Santos
- Laboratório Nacional de Luz Síncrotron - Centro Nacional de Pesquisa em Energia e Materiais - CP 6192, 13083-970 Campinas, SP, Brazil
| | - Gustavo Lorencini M P Rodrigues
- Laboratório Nacional de Luz Síncrotron - Centro Nacional de Pesquisa em Energia e Materiais - CP 6192, 13083-970 Campinas, SP, Brazil
| | - Andre Silva Rocha
- Laboratório Nacional de Luz Síncrotron - Centro Nacional de Pesquisa em Energia e Materiais - CP 6192, 13083-970 Campinas, SP, Brazil
| | - Horacio Ribeiro de Moraes
- Laboratório Nacional de Luz Síncrotron - Centro Nacional de Pesquisa em Energia e Materiais - CP 6192, 13083-970 Campinas, SP, Brazil
| | - Julio Criginski Cezar
- Laboratório Nacional de Luz Síncrotron - Centro Nacional de Pesquisa em Energia e Materiais - CP 6192, 13083-970 Campinas, SP, Brazil
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Andersen TK, Cook S, Benda E, Hong H, Marks LD, Fong DD. Development of a hybrid molecular beam epitaxy deposition system for in situ surface x-ray studies. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:033905. [PMID: 29604768 DOI: 10.1063/1.5008369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
A portable metalorganic gas delivery system designed and constructed to interface with an existing molecular beam epitaxy chamber at beamline 33-ID-E of the Advanced Photon Source is described. This system offers the ability to perform in situ X-ray measurements of complex oxide growth via hybrid molecular beam epitaxy. The performance of the hybrid molecular beam epitaxy system while delivering metalorganic source materials is described. The high-energy X-ray scattering capabilities of the hybrid molecular beam epitaxy system are demonstrated both on oxide films grown solely from the metalorganic source and ABO3 oxide perovskites containing elements from both the metalorganic source and a traditional effusion cell.
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Affiliation(s)
- Tassie K Andersen
- Materials Science Division, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439, USA
| | - Seyoung Cook
- Materials Science Division, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439, USA
| | - Erika Benda
- Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439, USA
| | - Hawoong Hong
- Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439, USA
| | - Laurence D Marks
- Department of Materials Science and Engineering, Northwestern University, 2220 Campus Dr., Evanston, Illinois 60208, USA
| | - Dillon D Fong
- Materials Science Division, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439, USA
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7
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Andersen TK, Cook S, Wan G, Hong H, Marks LD, Fong DD. Layer-by-Layer Epitaxial Growth of Defect-Engineered Strontium Cobaltites. ACS APPLIED MATERIALS & INTERFACES 2018; 10:5949-5958. [PMID: 29346722 DOI: 10.1021/acsami.7b16970] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Control over structure and composition of (ABO3) perovskite oxides offers exciting opportunities since these materials possess unique, tunable properties. Perovskite oxides with cobalt B-site cations are particularly promising, as the range of the cation's stable oxidation states leads to many possible structural frameworks. Here, we report growth of strontium cobalt oxide thin films by molecular beam epitaxy, and conditions necessary to stabilize different defect concentration phases. In situ X-ray scattering is used to monitor structural evolution during growth, while in situ X-ray absorption near-edge spectroscopy is used to probe oxidation state and measure changes to oxygen vacancy concentration as a function of film thickness. Experimental results are compared to kinetically limited thermodynamic predictions, in particular, solute trapping, with semiquantitative agreement. Agreement between observations of dependence of cobaltite phase on oxidation activity and deposition rate, and predictions indicates that a combined experimental/theoretical approach is key to understanding phase behavior in the strontium cobalt oxide system.
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Affiliation(s)
- Tassie K Andersen
- Materials Science Division, Argonne National Laboratory , Argonne, Illinois 60439, United States
- Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States
| | - Seyoung Cook
- Materials Science Division, Argonne National Laboratory , Argonne, Illinois 60439, United States
- Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States
| | - Gang Wan
- Materials Science Division, Argonne National Laboratory , Argonne, Illinois 60439, United States
| | - Hawoong Hong
- Advanced Photon Source, Argonne National Laboratory , Argonne, Illinois 60439, United States
| | - Laurence D Marks
- Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States
| | - Dillon D Fong
- Materials Science Division, Argonne National Laboratory , Argonne, Illinois 60439, United States
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