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Thomsen JD, Han MG, Penn AN, Foucher AC, Geiwitz M, Burch KS, Dekanovsky L, Sofer Z, Liu Y, Petrovic C, Ross FM, Zhu Y, Narang P. Effect of Surface Oxidation and Crystal Thickness on the Magnetic Properties and Magnetic Domain Structures of Cr 2Ge 2Te 6. ACS NANO 2024; 18:13458-13467. [PMID: 38739873 DOI: 10.1021/acsnano.3c09858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
van der Waals (vdW) magnetic materials, such as Cr2Ge2Te6 (CGT), show promise for memory and logic applications. This is due to their broadly tunable magnetic properties and the presence of topological magnetic features such as skyrmionic bubbles. A systematic study of thickness and oxidation effects on magnetic domain structures is important for designing devices and vdW heterostructures for practical applications. Here, we investigate thickness effects on magnetic properties, magnetic domains, and bubbles in oxidation-controlled CGT crystals. We find that CGT exposed to ambient conditions for 5 days forms an oxide layer approximately 5 nm thick. This oxidation leads to a significant increase in the oxidation state of the Cr ions, indicating a change in local magnetic properties. This is supported by real-space magnetic texture imaging through Lorentz transmission electron microscopy. By comparing the thickness-dependent saturation field of oxidized and pristine crystals, we find that oxidation leads to a nonmagnetic surface layer that is thicker than the oxide layer alone. We also find that the stripe domain width and skyrmionic bubble size are strongly affected by the crystal thickness in pristine crystals. These findings underscore the impact of thickness and surface oxidation on the properties of CGT, such as saturation field and domain/skyrmionic bubble size, and suggest a pathway for manipulating magnetic properties through a controlled oxidation process.
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Affiliation(s)
- Joachim Dahl Thomsen
- Division of Physical Sciences, College of Letters and Science, University of California, Los Angeles, Los Angeles, California 90095, United States
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Myung-Geun Han
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Aubrey N Penn
- MIT.nano, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Alexandre C Foucher
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Michael Geiwitz
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Kenneth Stephen Burch
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Lukas Dekanovsky
- Department of Inorganic Chemistry, University of Chemistry and Technology Prague, Technická 5, Prague 6 166 28, Czech Republic
| | - Zdeněk Sofer
- Department of Inorganic Chemistry, University of Chemistry and Technology Prague, Technická 5, Prague 6 166 28, Czech Republic
| | - Yu Liu
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973, United States
- Center for Correlated Matter and School of Physics, Zhejiang University, Hangzhou 310058, People's Republic of China
| | - Cedomir Petrovic
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973, United States
- Shanghai Key Laboratory of Material Frontiers Research in Extreme Environments (MFree), Shanghai Advanced Research in Physical Sciences (SHARPS), Pudong, Shanghai 201203, People's Republic of China
| | - Frances M Ross
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Yimei Zhu
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Prineha Narang
- Division of Physical Sciences, College of Letters and Science, University of California, Los Angeles, Los Angeles, California 90095, United States
- Electrical and Computer Engineering Department, University of California, Los Angeles, Los Angeles, California 90095, United States
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Klein J, Pham T, Thomsen JD, Curtis JB, Denneulin T, Lorke M, Florian M, Steinhoff A, Wiscons RA, Luxa J, Sofer Z, Jahnke F, Narang P, Ross FM. Control of structure and spin texture in the van der Waals layered magnet CrSBr. Nat Commun 2022; 13:5420. [PMID: 36109520 PMCID: PMC9478124 DOI: 10.1038/s41467-022-32737-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 08/03/2022] [Indexed: 11/14/2022] Open
Abstract
Controlling magnetism at nanometer length scales is essential for realizing high-performance spintronic, magneto-electric and topological devices and creating on-demand spin Hamiltonians probing fundamental concepts in physics. Van der Waals (vdW)-bonded layered magnets offer exceptional opportunities for such spin texture engineering. Here, we demonstrate nanoscale structural control in the layered magnet CrSBr with the potential to create spin patterns without the environmental sensitivity that has hindered such manipulations in other vdW magnets. We drive a local phase transformation using an electron beam that moves atoms and exchanges bond directions, effectively creating regions that have vertical vdW layers embedded within the initial horizontally vdW bonded exfoliated flakes. We calculate that the newly formed two-dimensional structure is ferromagnetically ordered in-plane with an energy gap in the visible spectrum, and weak antiferromagnetism between the planes, suggesting possibilities for creating spin textures and quantum magnetic phases.
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Affiliation(s)
- J Klein
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
| | - T Pham
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - J D Thomsen
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - J B Curtis
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
- Department of Physics, Harvard University, Cambridge, MA, USA
| | - T Denneulin
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, 52425, Jülich, Germany
| | - M Lorke
- Institut für Theoretische Physik, Universität Bremen, P.O. Box 330 440, 28334, Bremen, Germany
| | - M Florian
- Institut für Theoretische Physik, Universität Bremen, P.O. Box 330 440, 28334, Bremen, Germany
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, USA
| | - A Steinhoff
- Institut für Theoretische Physik, Universität Bremen, P.O. Box 330 440, 28334, Bremen, Germany
| | - R A Wiscons
- Department of Chemistry, Columbia University, New York, 10027, NY, USA
| | - J Luxa
- Department of Inorganic Chemistry, University of Chemistry and Technology Prague, Technická 5, 166 28, Prague 6, Czech Republic
| | - Z Sofer
- Department of Inorganic Chemistry, University of Chemistry and Technology Prague, Technická 5, 166 28, Prague 6, Czech Republic
| | - F Jahnke
- Institut für Theoretische Physik, Universität Bremen, P.O. Box 330 440, 28334, Bremen, Germany
| | - P Narang
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA.
| | - F M Ross
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
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Manzo S, Strohbeen PJ, Lim ZH, Saraswat V, Du D, Xu S, Pokharel N, Mawst LJ, Arnold MS, Kawasaki JK. Pinhole-seeded lateral epitaxy and exfoliation of GaSb films on graphene-terminated surfaces. Nat Commun 2022; 13:4014. [PMID: 35851271 PMCID: PMC9293962 DOI: 10.1038/s41467-022-31610-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2021] [Accepted: 06/17/2022] [Indexed: 11/25/2022] Open
Abstract
Remote epitaxy is a promising approach for synthesizing exfoliatable crystalline membranes and enabling epitaxy of materials with large lattice mismatch. However, the atomic scale mechanisms for remote epitaxy remain unclear. Here we experimentally demonstrate that GaSb films grow on graphene-terminated GaSb (001) via a seeded lateral epitaxy mechanism, in which pinhole defects in the graphene serve as selective nucleation sites, followed by lateral epitaxy and coalescence into a continuous film. Remote interactions are not necessary in order to explain the growth. Importantly, the small size of the pinholes permits exfoliation of continuous, free-standing GaSb membranes. Due to the chemical similarity between GaSb and other III-V materials, we anticipate this mechanism to apply more generally to other materials. By combining molecular beam epitaxy with in-situ electron diffraction and photoemission, plus ex-situ atomic force microscopy and Raman spectroscopy, we track the graphene defect generation and GaSb growth evolution a few monolayers at a time. Our results show that the controlled introduction of nanoscale openings in graphene provides an alternative route towards tuning the growth and properties of 3D epitaxial films and membranes on 2D material masks. Remote epitaxy represents a promising method for the synthesis of thin films on lattice-mismatched substrates, but its atomic-scale mechanisms are still unclear. Here, the authors demonstrate the growth of exfoliatable GaSb films on graphene-terminated GaSb (001) via seeded lateral epitaxy, showing that pinhole defects in graphene serve as selective nucleation sites.
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Affiliation(s)
- Sebastian Manzo
- Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Patrick J Strohbeen
- Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Zheng Hui Lim
- Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Vivek Saraswat
- Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Dongxue Du
- Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Shining Xu
- Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Nikhil Pokharel
- Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Luke J Mawst
- Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Michael S Arnold
- Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Jason K Kawasaki
- Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA.
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Ghamsari M, Madrakian T, Afkhami A, Ahmadi M. Self-assembled graphene-based microfibers with eclectic optical properties. Sci Rep 2021; 11:5451. [PMID: 33750859 PMCID: PMC7943562 DOI: 10.1038/s41598-021-84940-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2020] [Accepted: 02/23/2021] [Indexed: 01/31/2023] Open
Abstract
The construction of graphene-based microfibers with reinforced mechanical and electrical properties has been the subject of numerous researches in recent years. However, the fabrication of graphene-based fibers with remarkable optical features still remains a challenge and has not been addressed so far. This paper aims to report a series of flexible self-assembled fibers, synthesized through a few-minute sonication of thermally oxidized graphene oxide nanosheets, so-called Nanoporous Over-Oxidized Graphene (NOG), in an acidic medium. These free-standing glassy fibers were classified into four distinct morphological structures and displayed a collection of intriguing optical properties comprising high transparency, strong birefringence, fixed body colorations (e.g. colorless, blue, green, and red), tunable interference marginal colorations, UV-visible-near IR fluorescence, and upconversion emissions. Moreover, they exhibited high chemical stability in strongly acidic, basic, and oxidizing media. The foregoing notable attributes introduce the NOG fiber as a promising candidate both for the construction of graphene-based photoluminescent textiles and the development of a wide variety of optical applications.
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Affiliation(s)
- Mahdi Ghamsari
- Faculty of Chemistry, Bu-Ali Sina University, Hamedan, 6517838695, Iran
| | - Tayyebeh Madrakian
- Faculty of Chemistry, Bu-Ali Sina University, Hamedan, 6517838695, Iran.
| | - Abbas Afkhami
- Faculty of Chemistry, Bu-Ali Sina University, Hamedan, 6517838695, Iran
| | - Mazaher Ahmadi
- Faculty of Chemistry, Bu-Ali Sina University, Hamedan, 6517838695, Iran
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Schlichting KP, Poulikakos D. Selective Etching of Graphene Membrane Nanopores: From Molecular Sieving to Extreme Permeance. ACS APPLIED MATERIALS & INTERFACES 2020; 12:36468-36477. [PMID: 32805790 DOI: 10.1021/acsami.0c07277] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Two-dimensional materials are the essential building blocks of breakthrough membrane technologies due to minimal permeation barriers across atomically thin pores. Tunable pore size fabrication combined with independently controlled pore number density is necessary for outstanding performance but remains a challenge. There is a great need for parallel, upscalable methods that can control pore size from sub-nm to >5 nm, a pore size range required for membranes with effective molecular separation. Here we report a dry, facile, and scalable process introducing atomic defects by design, followed by selective etching of graphene edge atoms able to controllably expand the nanopore dimensions from sub-nm to 5 nm. The attainable average pore sizes at 1015 m-2 pore density promise applicability to various separation applications. We investigate the gas permeation and separation mechanisms, finding that these membranes display molecular sieving (H2/CH4 separation factor = 9.3; H2 permeance = 3370 gas permeation units (GPU)) and reveal the presence of interweaved transport phenomena of pore chemistry, surface flow, and gas molecule momentum transfer. We observe the smooth transition from molecular sieving to effusion at unprecedented permeance (H2/CH4 separation factor = 3.7; H2 permeance = 107 GPU). Our scalable graphene membrane fabrication approach in combination with sub-5 nm pores opens a new route employing 2D membranes to study gas transport and effectively paving the way to industrial applications.
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Affiliation(s)
- Karl-Philipp Schlichting
- Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, CH-8092 Zurich, Switzerland
| | - Dimos Poulikakos
- Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, CH-8092 Zurich, Switzerland
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