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El-Sherif H, Briggs N, Bersch B, Pan M, Hamidinejad M, Rajabpour S, Filleter T, Kim KW, Robinson J, Bassim ND. Scalable Characterization of 2D Gallium-Intercalated Epitaxial Graphene. ACS Appl Mater Interfaces 2021; 13:55428-55439. [PMID: 34780159 DOI: 10.1021/acsami.1c14091] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Scalable synthesis of two-dimensional gallium (2D-Ga) covered by graphene layers was recently realized through confinement heteroepitaxy using silicon carbide substrates. However, the thickness, uniformity, and area coverage of the 2D-Ga heterostructures have not previously been studied with high-spatial resolution techniques. In this work, we resolve and measure the 2D-Ga heterostructure thicknesses using scanning electron microscopy (SEM). Utilizing multiple correlative methods, we find that SEM image contrast is directly related to the presence of uniform bilayer Ga at the interface and a variation of the number of graphene layers. We also investigate the origin of SEM contrast using both experimental measurements and theoretical calculations of the surface potentials. We find that a carbon buffer layer is detached due to the gallium intercalation, which increases the surface potential as an indication of the 2D-Ga presence. We then scale up the heterostructure characterization over a few-square millimeter area by segmenting SEM images, each acquired with nanometer-scale in-plane resolution. This work leverages the spectroscopic imaging capabilities of SEM that allows high-spatial resolution imaging for tracking intercalants, identifying relative surface potentials, determining the number of 2D layers, and further characterizing scalability and uniformity of low-dimensional materials.
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Affiliation(s)
- Hesham El-Sherif
- Department of Materials Science and Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S4L8, Canada
| | - Natalie Briggs
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, State College, Pennsylvania 16802, United States
| | - Brian Bersch
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, State College, Pennsylvania 16802, United States
| | - Minghao Pan
- Department of Physics and Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Mahdi Hamidinejad
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario M5S3G8, Canada
| | - Siavash Rajabpour
- Department of Chemical Engineering, The Pennsylvania State University, University Park, State College, Pennsylvania 16802, United States
| | - Tobin Filleter
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario M5S3G8, Canada
| | - Ki Wook Kim
- Department of Physics and Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Joshua Robinson
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, State College, Pennsylvania 16802, United States
| | - Nabil D Bassim
- Department of Materials Science and Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S4L8, Canada
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Anam B, Gaston N. Two-dimensional aluminium, gallium, and indium metallic crystals by first-principles design. J Phys Condens Matter 2021; 33:125901. [PMID: 33321476 DOI: 10.1088/1361-648x/abd3d9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Accepted: 12/15/2020] [Indexed: 06/12/2023]
Abstract
Rapidly emerging two-dimensional (2D) atomic layer crystals exhibit diverse, tunable electronic properties. They appear to be more flexible than 3D crystals with greater versatility and improved functionality in a wide range of potential applications. Among these 2D materials, metallic crystals are relatively unexplored although two allotropes of gallenene (2D gallium) have been synthesized on a range of substrates. Based on these experimental findings, we investigate systematically the group 13 metals using first-principles density functional theory calculations and an unbiased structural search. In this study, the electronic structure, bonding characteristics, and phonon properties of predicted 2D allotropes of group 13 metals are calculated, including the expected effects of strain induced by substrates on the dynamical stability. Theoretical results predict that most group 13 elements have one or more stable 2D allotropes with the preferred allotrope depending on the cell shape relaxation and strain, indicating that the substrate will determine the overall allotrope preferred. This demonstrates a new avenue for the discovery of thermodynamically stable 2D metallic layers, with properties potentially suitable for electronic and optoelectronic applications.
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Affiliation(s)
- Bushra Anam
- MacDiarmid Institute for Advanced Materials and Nanotechnology, The Department of Physics, University of Auckland, Private Bag 92019, Auckland 1010, New Zealand
| | - Nicola Gaston
- MacDiarmid Institute for Advanced Materials and Nanotechnology, The Department of Physics, University of Auckland, Private Bag 92019, Auckland 1010, New Zealand
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