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. 2023 Jan 11;13(1):569.
doi: 10.1038/s41598-022-24044-5.

High-performance Fe(Se,Te) films on chemical CeO2-based buffer layers

L Piperno  1 , A Vannozzi  2 , A Augieri  2 , A Masi  2 , A Mancini  2 , A Rufoloni  2 , G Celentano  2 , V Braccini  3 , M Cialone  3 , M Iebole  3   4 , N Manca  3 , A Martinelli  3 , M Meinero  3   4 , M Putti  4 , A Meledin  5   6
Affiliations

High-performance Fe(Se,Te) films on chemical CeO2-based buffer layers

L Piperno et al. Sci Rep. .

Abstract

The fabrication of a Fe-based coated conductor (CC) becomes possible when Fe(Se,Te) is grown as an epitaxial film on a metallic oriented substrate. Thanks to the material's low structural anisotropy, less strict requirements on the template microstructure allow for the design of a simplified CC architecture with respect to the REBCO multi-layered layout. This design, though, still requires a buffer layer to promote the oriented growth of the superconducting film and avoid diffusion from the metallic template. In this work, Fe(Se,Te) films are grown on chemically-deposited, CeO2-based buffer layers via pulsed laser deposition, and excellent properties are obtained when a Fe(Se,Te) seed layer is used. Among all the employed characterization techniques, transmission electron microscopy proved essential to determine the actual effect of the seed layer on the final film properties. Also, systematic investigation of the full current transport properties J(θ, H, T) is carried out: Fe(Se,Te) samples are obtained with sharp superconducting transitions around 16 K and critical current densities exceeding 1 MA cm-2 at 4.2 K in self-field. The in-field and angular behavior of the sample are in line with data from the literature. These results are the demonstration of the feasibility of a Fe-based CC, with all the relative advantages concerning process simplification and cost reduction.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
AFM images of a CZO/YSZ film obtained via MOD.
Figure 2
Figure 2
Upper panel: θ–2θ spectra of a Fe(Se,Te) film (seed layer + top layer) deposited on a MOD CZO buffer. On the left, highlight of the double phase feature of the Fe(Se,Te) signals; Lower panel, : XRD (111) ϕ-scans of the Fe(Se,Te) film and of the underlying MOD CZO buffer.
Figure 3
Figure 3
SEM images of a Fe(Se,Te) film (seed layer + top layer) deposited on a MOD CZO buffer.
Figure 4
Figure 4
TEM images of a Fe(Se,Te) film (seed layer + top layer) deposited on a MOD CZO buffer. From the left: HAADF image of the film cross section, EDX mapping of Ce, Te, Se and Fe distribution in the same region.
Figure 5
Figure 5
TEM images of the seed/top interface of the Fe(Se,Te) film shown in Fig. 4. From the top-left: HAADF image of the interface, EDX mapping of O, Se, Te in the same region, schematic representation of the lines used to calculate the EDX profiles, EDX profile across a low-intensity region, EDX profile across the interface.
Figure 6
Figure 6
Resistive transitions in applied magnetic fields up to 18 T in a Fe(Se,Te) film (seed layer + top layer) deposited on a MOD CZO-buffered YSZ. Left panel: H//c, right panel: H//ab.
Figure 7
Figure 7
Temperature dependence of Hc2 derived from R versus T measurements according to the 90% method in a Fe(Se,Te) film (seed layer + top layer) deposited on a MOD CZO-buffered YSZ. Full symbols: H//c, empty symbols: H//ab. Inset: anisotropy parameter calculated as γHc2 = Hc2//ab/Hc2//c.
Figure 8
Figure 8
Magnetic field dependence of Jc at different temperatures in a Fe(Se,Te) film (seed layer + top layer) deposited on a MOD CZO-buffered YSZ. Full symbols: H//c, empty symbols: H//ab.
Figure 9
Figure 9
Jc anisotropy γJ = Jc (H//ab)/Jc (H//c) as a function of applied field in the 0–18 T field range between 4 and 12 K.
Figure 10
Figure 10
Normalized Fp curves versus reduced field at θ = 0° and θ = 90° (inset) showing the overlap of the curves in the whole temperature/field investigated regime.
Figure 11
Figure 11
Temperature dependence of Hirr derived from R versus T measurements (full symbols) and the pinning force fits (empty symbols) in a Fe(Se,Te) film (seed layer + top layer) deposited on a MOD CZO-buffered YSZ. circles: H//c, squares: H//ab. Inset: anisotropy parameter calculated as γHirr = Hirr//ab/Hirr//c.
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