Co alloy media made on amorphous carbon substrate

Kuwabara, M.; Sato, M.; Onishi, Y.; Visokay, M.R.; Hayashi, Hidetaka; Inoue, Hidenari; Muramatsu, Keiichi

doi:10.1063/1.352502

Cited by 15 publications

(2 citation statements)

References 2 publications

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“…Figure 3 compares the surface morphology of superconducting films after thermal processing for 1 hour at 600 • C prepared without (figure 3(a)) and with (figure 3 layers (~6 × 10 −6 K −1 ) [23] and the glassy carbon substrate (3 × 10 −6 K −1 ) [22]. Upon heating, the Mg layer expands more than the surrounding B and C substrate layers [12], which could induce the blistering observed in unmixed films.…”

Section: Resultsmentioning

confidence: 99%

Superconducting films of MgB₂ via ion beam mixing of Mg/B multilayers

Beckham

Aji

Baker

et al. 2020

J. Phys. D: Appl. Phys.

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The growth of smooth superconducting MgB2 films in a non-epitaxial regime is challenging. Here, we study the formation of superconducting MgB2 films by solid-phase reactive inter-diffusion of sputter-deposited Mg/B multilayers, employing ion beam mixing to disperse the multilayers prior to thermal annealing. The multilayers are intermixed by room-temperature bombardment with 500 keV Xe ions to doses up to 4 × 1016 cm−2, followed by thermal annealing to form MgB2. Results show that such an intermixing step leads to a dramatic reduction in surface roughness of superconducting films. However, lattice defects produced by ion bombardment reduce the critical superconducting transition temperature, an effect which scales monotonically with ion dose. The critical temperature can be recovered by an additional defect annealing step at .

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Section: Resultsmentioning

confidence: 99%

Superconducting films of MgB₂ via ion beam mixing of Mg/B multilayers

Beckham

Aji

Baker

et al. 2020

J. Phys. D: Appl. Phys.

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“…In contrast, the thinnest films (25 and 55 nm) do not exhibit blistering (figure 6(e)). Such blistering can be attributed to compressive stresses due to a difference in the coefficient of thermal expansion between glassy carbon (3 × 10 −6 K −1 ) [47] and B (∼6 × 10 −6 K −1 ) [48], presumably exacerbated by poor adhesion of the film. Furthermore, the nearly twofold increase in volume of the film during vapor processing likely imposes an upper limit on stable film thickness, irrespective of the stress related to thermal expansion.…”

Section: Film Thickness Dependencementioning

confidence: 99%

Vapor annealing synthesis of non-epitaxial MgB₂films on glassy carbon

Baker

Aji

Bae

et al. 2018

Supercond. Sci. Technol.

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We describe the fabrication and characterization of 25-800 nm thick MgB 2 films on glassy carbon substrates by Mg vapor annealing of sputter-deposited amorphous B films. Results demonstrate a critical role of both the initial B film thickness and the temperature-time profile on the microstructure, elemental composition, and superconducting properties of the resultant MgB 2 films. Films with thicknesses of 55 nm and below exhibit a smooth surface, with a roughness of 1.1 nm, while thicker films have surface morphology consisting of elongated nano-crystallites. The suppression of the superconducting transition temperature for thin films scales linearly with the oxygen impurity concentration and also correlates with the amount of lattice disorder probed by Raman scattering. The best results are obtained by a rapid (12 min) anneal at 850 °C with large temperature ramp and cooling rates of ∼540 °C min −1 . Such fast processing suppresses the deleterious oxygen uptake.

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