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Varshney S, Choo S, Thompson L, Yang Z, Shah J, Wen J, Koester SJ, Mkhoyan KA, McLeod AS, Jalan B. Hybrid Molecular Beam Epitaxy for Single-Crystalline Oxide Membranes with Binary Oxide Sacrificial Layers. ACS NANO 2024; 18:6348-6358. [PMID: 38314696 DOI: 10.1021/acsnano.3c11192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2024]
Abstract
The advancement in thin-film exfoliation for synthesizing oxide membranes has led to possibilities for creating artificially assembled heterostructures with structurally and chemically incompatible materials. The sacrificial layer method is a promising approach to exfoliate as-grown films from a compatible material system, allowing for their integration with dissimilar materials. Nonetheless, the conventional sacrificial layers often possess an intricate stoichiometry, thereby constraining their practicality and adaptability, particularly when considering techniques such as molecular beam epitaxy (MBE). This is where easy-to-grow binary alkaline-earth-metal oxides with a rock salt crystal structure are useful. These oxides, which include (Mg, Ca, Sr, Ba)O, can be used as a sacrificial layer covering a much broader range of lattice parameters compared to conventional sacrificial layers and are easily dissolvable in deionized water. In this study, we show the epitaxial growth of the single-crystalline perovskite SrTiO3 (STO) on sacrificial layers consisting of crystalline SrO, BaO, and Ba1-xCaxO films, employing a hybrid MBE method. Our results highlight the rapid (≤5 min) dissolution of the sacrificial layer when immersed in deionized water, facilitating the fabrication of millimeter-sized STO membranes. Using high-resolution X-ray diffraction, atomic-force microscopy, scanning transmission electron microscopy, impedance spectroscopy, and scattering-type near-field optical microscopy (SNOM), we demonstrate single-crystalline STO membranes with bulk-like intrinsic dielectric properties. The employment of alkaline earth metal oxides as sacrificial layers is likely to simplify membrane synthesis, particularly with MBE, thus expanding the research and application possibilities.
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Affiliation(s)
- Shivasheesh Varshney
- Department of Chemical Engineering and Materials Science, University of Minnesota, Twin Cities, Minnesota 55455, United States
| | - Sooho Choo
- Department of Chemical Engineering and Materials Science, University of Minnesota, Twin Cities, Minnesota 55455, United States
| | - Liam Thompson
- School of Physics and Astronomy, University of Minnesota, Twin Cities, Minnesota 55455, United States
| | - Zhifei Yang
- Department of Chemical Engineering and Materials Science, University of Minnesota, Twin Cities, Minnesota 55455, United States
- School of Physics and Astronomy, University of Minnesota, Twin Cities, Minnesota 55455, United States
| | - Jay Shah
- Department of Chemical Engineering and Materials Science, University of Minnesota, Twin Cities, Minnesota 55455, United States
| | - Jiaxuan Wen
- Department of Electrical and Computer Engineering, University of Minnesota, Twin Cities, Minnesota 55455, United States
| | - Steven J Koester
- Department of Electrical and Computer Engineering, University of Minnesota, Twin Cities, Minnesota 55455, United States
| | - K Andre Mkhoyan
- Department of Chemical Engineering and Materials Science, University of Minnesota, Twin Cities, Minnesota 55455, United States
| | - Alexander S McLeod
- School of Physics and Astronomy, University of Minnesota, Twin Cities, Minnesota 55455, United States
| | - Bharat Jalan
- Department of Chemical Engineering and Materials Science, University of Minnesota, Twin Cities, Minnesota 55455, United States
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