Crystal Orientation and Thickness Dependence of the Superconducting Transition Temperature of TetragonalFeSe1−xThin Films

Abstract

Superconductivity was recently found in the tetragonal phase FeSe. A structural transformation from tetragonal to orthorhombic (or monoclinic, depending on point of view) was observed at low temperature, but was not accompanied by a magnetic ordering as commonly occurs in the parent compounds of FeAs-based superconductors. Here, we report the correlation between structural distortion and superconductivity in FeSe(1-x) thin films with different preferred growth orientations. The films with preferred growth along the c axis show a strong thickness dependent suppression of superconductivity and low temperature structural distortion. In contrast, both properties are less affected in the films with (101) preferred orientation. These results suggest that the low temperature structural distortion is closely associated with the superconductivity of this material.

Superconducting property and Fe valence state of FeSe thick films grown from high temperature solution

“…Recently, the thickness and orientation dependences of T c were reported for the epitaxial FeSe films grown at 320-500 • C by pulsed laser deposition [11]. The (0 0 1) textured films showed a significantly depressed T c when their thickness was less than 1.0 m, while the (1 0 1) textured films exhibited only small T c variation with thickness [11]. As mentioned earlier, the film thickness in this study was about 1.5 m and therefore should not be relevant.…”

Superconducting properties of iron chalcogenide thin films

“…Wang et al [43] deposited smooth tetragonal FeSe 1−x films on (001) MgO substrates by PLD. They studied the effect of low-temperature distortion on superconductivity and crystallinity.…”

A Simple Fabrication of FeSe Superconductors with High Upper Critical Field

“…In addition, it is the As-free compound, and hence less poisonous than the other kinds of pnictide compounds. Tetragonal FeSe (doped or undoped) in various modalities have been fabricated by many kinds of methods, e.g., polycrystal powder [10][11][12][13], single crystal [14,15], thin films [16,17]. However, due to the growth challenge of the pnictide materials, the fabrication processes of all the above methods are somewhat complicated.…”