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X-ray diffraction data on Fe(Se,Te) thin film deposited LAO: in (a) the symmetrical scan, in (b) scans in the direction . The out of plane and in plane epitaxial quality of the growth is shown in panels (c) and (d) where a scan (rocking curve) of the 001 reflection and a scan of the 101 reflection are plotted, respectively.
The -axis (a) and (b) values vs film thickness for several Fe(Se,Te) films on LAO (○) STO (◻) and Y:ZrO (△): the superconducting critical temperature reaches a maximum value of 21 K for a thickness of about 200 nm; for the same thickness value a minimum value of the in-plane cell parameter is observed. In (c): the resistivities vs temperature of several films on LAO with different thickness (9, 18, 36, 72, 150, 200, 280, and 420 nm): the room temperature resistivity monotonically decreases increasing the thickness. In the inset the detail of superconducting transition for some films.
Atomic force microscope images of the initial and intermediate stages of the growth of a Fe(Se,Te) thin film on LAO substrate. Fe(Se,Te) initially nucleates in the form of small islands (a) that concentrate at the step edges (b); the islands coalesce (c) and a uniform coverage is obtained (d).
In (a) the transition temperatures of several Fe(Se,Te) films on LAO (○) STO (◻) and Y:ZrO (△) are reported as a function of the in-plane cell parameter . In (b) and (c) the transition temperatures of films deposited on LAO are plotted as a function of the Fe–(Se,Te) bond length and of the (Se,Te)–Fe–(Se,Te) bond angle, respectively. The stars represent, in all the panel the corresponding bulk values. As an eye guideline the linear fit of the data (dashed lines) is added in all the panels.
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