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Bromley D, Wright AJ, Jones LAH, Swallow JEN, Beesley T, Batty R, Weatherup RS, Dhanak VR, O'Brien L. Electron beam evaporation of superconductor-ferromagnet heterostructures. Sci Rep 2022; 12:7786. [PMID: 35545648 PMCID: PMC9095728 DOI: 10.1038/s41598-022-11828-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 04/29/2022] [Indexed: 11/09/2022] Open
Abstract
We report on the electronic and magnetic properties of superconductor-ferromagnet heterostructures fabricated by electron beam evaporation on to unheated thermally oxidised Si substrates. Polycrystalline Nb thin films (5 to 50 nm thick) were shown to possess reliably high superconducting critical temperatures (\documentclass[12pt]{minimal}
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\begin{document}$$T_{c}$$\end{document}Tc), which correlate well with the residual resistivity ratio (RRR) of the film. These properties improved during ex-situ annealing, resulting in \documentclass[12pt]{minimal}
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\begin{document}$${\Delta }T_{c}$$\end{document}ΔTc and \documentclass[12pt]{minimal}
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\begin{document}$${\Delta }$$\end{document}ΔRRR increases of up 2.2 K (\documentclass[12pt]{minimal}
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\begin{document}$$\sim$$\end{document}∼ 40% of the pre-annealed \documentclass[12pt]{minimal}
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\begin{document}$$T_{c}$$\end{document}Tc) and 0.8 (\documentclass[12pt]{minimal}
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\begin{document}$$\sim$$\end{document}∼ 60% of the pre-annealed RRR) respectively. Nb/Pt/Co/Pt heterostructures showed substantial perpendicular anisotropy in the ultrathin limit (≤ 2.5 nm), even in the extreme limit of Pt(0.8 nm)/Co(1 nm)/Pt(0.6 nm). These results point to the use of electron beam evaporation as route to line-of-sight deposited, low-thickness, high quality Nb-based superspintronic multilayers.
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Affiliation(s)
- D Bromley
- Department of Physics, University of Liverpool, Liverpool, L69 7ZE, UK
| | - A J Wright
- Department of Physics, University of Liverpool, Liverpool, L69 7ZE, UK
| | - L A H Jones
- Department of Physics, University of Liverpool, Liverpool, L69 7ZE, UK
| | - J E N Swallow
- Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK
| | - T Beesley
- Department of Physics, University of Liverpool, Liverpool, L69 7ZE, UK
| | - R Batty
- Department of Physics, University of Liverpool, Liverpool, L69 7ZE, UK
| | - R S Weatherup
- Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK
| | - V R Dhanak
- Department of Physics, University of Liverpool, Liverpool, L69 7ZE, UK
| | - L O'Brien
- Department of Physics, University of Liverpool, Liverpool, L69 7ZE, UK.
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Cabrero-Vilatela A, Alexander-Webber JA, Sagade AA, Aria AI, Braeuninger-Weimer P, Martin MB, Weatherup RS, Hofmann S. Atomic layer deposited oxide films as protective interface layers for integrated graphene transfer. Nanotechnology 2017; 28:485201. [PMID: 29039352 DOI: 10.1088/1361-6528/aa940c] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The transfer of chemical vapour deposited graphene from its parent growth catalyst has become a bottleneck for many of its emerging applications. The sacrificial polymer layers that are typically deposited onto graphene for mechanical support during transfer are challenging to remove completely and hence leave graphene and subsequent device interfaces contaminated. Here, we report on the use of atomic layer deposited (ALD) oxide films as protective interface and support layers during graphene transfer. The method avoids any direct contact of the graphene with polymers and through the use of thicker ALD layers (≥100 nm), polymers can be eliminated from the transfer-process altogether. The ALD film can be kept as a functional device layer, facilitating integrated device manufacturing. We demonstrate back-gated field effect devices based on single-layer graphene transferred with a protective Al2O3 film onto SiO2 that show significantly reduced charge trap and residual carrier densities. We critically discuss the advantages and challenges of processing graphene/ALD bilayer structures.
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Affiliation(s)
- A Cabrero-Vilatela
- Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, United Kingdom
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