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Title: Origin of the emergence of higher T c than bulk in iron chalcogenide thin films

Fabrication of epitaxial FeSe xTe 1-x thin films using pulsed laser deposition (PLD) enables improving their superconducting transition temperature (T c) by more than ~40% than their bulk T c. Intriguingly, T c enhancement in FeSe xTe 1-x thin films has been observed on various substrates and with different Se content, x. To date, various mechanisms for T c enhancement have been reported, but they remain controversial in universally explaining the T c improvement in the FeSe xTe 1-x films. In this report, we demonstrate that the controversies over the mechanism of T c enhancement are due to the abnormal changes in the chalcogen ratio (Se:Te) during the film growth and that the previously reported T c enhancement in FeSe 0.5Te 0.5 thin films is caused by a remarkable increase of Se content. Although our FeSe xTe 1-x thin films were fabricated via PLD using a Fe 0.94Se 0.45Te 0.55 target, the precisely measured composition indicates a Se-rich FeSe xTe 1-x (0.6 < x < 0.8) as ascertained through accurate compositional analysis by both wavelength dispersive spectroscopy (WDS) and Rutherford backscattering spectrometry (RBS). We suggest that the origin of the abnormal composition change is the difference in the thermodynamic propertiesmore » of ternary FeSe xTe 1-x, based on first principle calculations.« less
Authors:
 [1] ;  [2] ;  [3] ;  [1] ;  [4] ;  [5] ;  [2] ;  [1] ;  [1] ;  [6] ;  [6] ;  [4] ;  [1] ;  [3] ;  [2] ; ORCiD logo [1]
  1. Gwangju Inst. of Science and Technology (GIST), Gwangju (South Korea). School of Materials Science and Engineering
  2. Univ. of Wisconsin, Madison, WI (United States). Dept. of Materials Science and Engineering
  3. Kyungpook National Univ., Daegu (Korea, Republic of). Dept. of Physics
  4. Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab. (MagLab), Applied Superconductivity Center
  5. Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Science Dept.
  6. Peking Univ., Beijing (China). Electron Microscopy Lab., School of Physics
Publication Date:
Report Number(s):
BNL-114442-2017-JA
Journal ID: ISSN 2045-2322; R&D Project: PO010; KC0201060
Grant/Contract Number:
SC0012704; FG02-06ER46327
Type:
Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 7; Journal Issue: 1; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Research Foundation of Korea (NRF)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Surfaces, interfaces and thin films; Superconducting properties and materials
OSTI Identifier:
1412666