Abstract
Two-dimensional (2D) superconductors have intriguing physical properties and abundant potential applications. Recently, 2D superconducting α-Mo2C and facecentered cubic Mo2C have been controllably prepared and they bring new viewpoints to carbon-based superconductivity. Although molybdenum carbides (Mo-Cs) have multiple crystalline stacking orders, there are still few structures reported for the lack of higher energy supply during growth. In this study, we report a two-step vapor deposition method to grow superconducting η-Mo3C2 films with different thicknesses, with the assistance of controllable plasma power. The grown η-Mo3C2 films show polycrystalline characteristics, but they still present superior superconductivity. The 3.0-nm-thick film has the superconducting transition temperature of 5.38 K, and its electrical performances follow truly 2D superconducting transitions. This study will not only exhibit a robust superconducting η-Mo3C2 ultrathin film, but also provides a convenient growth way to realize more carbide-based heterostructures for future device applications.
摘要
二维超导体具有丰富的物理特性和非常广泛的潜在应用. 最近, 有报道制备出具有二维超导特性的α-Mo2C和面心立方Mo2C,这些材料为碳基超导的研究带来了新的方向. 碳化钼具有多种晶体结构, 除了目前已经被制备的种类外, 二维碳化钼尚没有新的晶体结构被制备出来, 这或许是因为在制备过程中缺乏额外的能量供给. 在本工作中, 我们进一步发展了两步气相沉积法, 通过有效调控等离子体作为外加能量供给, 成功制备出具有不同厚度和超导特性的二维η-Mo3C2薄膜. 虽然这种方法生长出的η-Mo3C22薄膜是多晶, 但这些薄膜仍然可以表现出良好的超导特性. 其中,3.0 nm厚的薄膜具有5.38 K的超导转变温度, 而且其电学性能很好地与二维超导特性吻合. 这项工作不仅证明了二维η-Mo3C2薄膜具有稳定和良好的超导特性, 而且还提供了一种更为便捷的生长方法, 这将进一步促进更多基于二维碳化物异质结构的应用性器件的便捷制备.
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Acknowledgements
This work was supported by the National Key R&D Program of China (2018YFA0305800), the Fundamental Research Funds for the Central Universities (020414380145 and 020414380153), the National Natural Science Foundation of China (11674154, 11761131010, 51972163, 11904163, 61974021 and 11525415), the Natural Science Foundation of Jiangsu Province (BK20190010), and the Fok Ying-Tong Education Foundation of China (171038). We thank Xiaoxiang Xi for help with electrical measurements by the superconducting magnet of 12 T.
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Gao L conceived and supervised the project, and designed the experiments. Shi W, Yu J and Xu J carried out the growth experiments and XPS, Raman and electrical measurements. Huang X and Liu W assisted in the electrical measurements. Tu X and Sun L performed TEM. Gao L, ShiWand Yu J wrote the manuscript, Xu J, Xu T and Sun L revised it, and all authors commented on it.
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The authors declare no competing financial interests.
Wei Shi received his bachelor degree from Nanjing University in 2016. Now, he is a master candidate under the supervision of Prof. Libo Gao at the School of Physics, Nanjing University. His research interest focuses on the controllable growth of 2D carbide materials.
Libo Gao is a professor at the School of Physics, Nanjing University. He received his bachelor degree from Dalian University of Technology and PhD degree from the Institute of Metal Research, Chinese Academy of Sciences. He worked as a research fellow at Graphene Research Center, National University of Singapore from 2011 to 2015. Since 2015, he has been working in Nanjing University as a full professor. His scientific interests focus on controllable preparation and physical properties of 2D materials.
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Shi, W., Yu, J., Xu, T. et al. Superconductivity in two-dimensional η-Mo3C2 films. Sci. China Mater. 64, 664–672 (2021). https://doi.org/10.1007/s40843-020-1459-x
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DOI: https://doi.org/10.1007/s40843-020-1459-x