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Chemical Composition Control at the Substrate Interface as the Key for FeSe Thin-Film Growth
Yukiko Obata1, Michiko Sato2, Yuji Kondo2
1Tokyo Tech World Research Hub Initiative (WRHI), Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8503, Japan.
ACS Applied Materials & Interfaces
|October 26, 2021
Summary
Superconductivity in iron selenium (FeSe) thin films is challenging. This study reveals flawed assumptions about the FeSe/MgO interface and proposes an iron (Fe) buffer layer to improve stoichiometry and nanostrain for enhanced superconductivity.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Thin Film Deposition
Background:
- Iron selenium (FeSe) is a fascinating binary compound with potential for superconductivity.
- Inducing superconductivity in FeSe thin films requires optimized engineering protocols.
- The film/substrate interface critically influences FeSe thin-film properties.
Purpose of the Study:
- To investigate the peculiarities of pulsed laser deposition in FeSe thin-film growth.
- To re-evaluate the commonly assumed FeSe/MgO interface properties (cleanliness and lattice-matching epitaxy).
- To propose strategies for improving superconductivity in ultrathin FeSe films.
Main Methods:
- Pulsed laser deposition of FeSe thin films.
- Analysis of the FeSe/MgO interface.
- Introduction of an iron (Fe) buffer layer for interface homogenization.
- Investigation of film texture control with preparation conditions.
Main Results:
- The FeSe/MgO interface is not clean and does not obey lattice-matching epitaxy; domain-matching epitaxy with chemical heterogeneity is observed.
- An Fe buffer layer homogenizes the film/substrate interface, improving stoichiometry and nanostrain control.
- Interface homogenization with an Fe buffer favors superconductivity in ultrathin FeSe films.
- Film texture control remains possible on a chemically homogenized FeSe/Fe interface.
Conclusions:
- Challenging conventional assumptions about the FeSe/MgO interface is crucial for understanding FeSe thin-film growth.
- Employing an Fe buffer layer is a promising strategy to enhance superconductivity in FeSe thin films by controlling interface properties.
- Further research into interface engineering can unlock the full potential of FeSe-based superconducting materials.
