Fluorescence X-ray absorption spectroscopy using a Ge pixel array detector: application to high-temperature...

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid State Chemistry

Background:

• High-temperature superconducting thin films are crucial for advanced electronic applications.
• Understanding their local atomic structure is key to optimizing performance.
• Existing methods can be limited by substrate interference and resolution.

Purpose of the Study:

• To develop and apply a novel X-ray absorption spectroscopy technique for probing the local structure of thin superconducting films.
• To accurately analyze the local CuO6 octahedron distortions in (La,Sr)2CuO4 thin films.
• To demonstrate the capability of the technique for low-temperature, high-accuracy measurements without substrate interference.

Main Methods:

• Utilized a 100-segment Germanium (Ge) pixel array detector for fluorescence X-ray absorption spectroscopy.
• Employed grazing-incidence angle (theta) optimization and azimuthal angle (phi) adjustment to obtain clear extended X-ray absorption fine structure (EXAFS) signals.
• Analyzed EXAFS oscillations to determine local structural parameters of the CuO6 octahedron.

Main Results:

• Successfully obtained smooth EXAFS oscillations for strained (La,Sr)2CuO4 thin-film single crystals.
• Quantified uniaxial distortion in the CuO6 octahedron, with changes in tetragonality around 5 x 10(-3).
• Correlated observed distortions with crystallographic lattice mismatch from LaSrAlO4 and SrTiO3 substrates.

Conclusions:

• The Ge pixel array detector enables accurate, real-time inspection of thin-film local structure.
• The technique effectively probes substrate-induced lattice distortions in high-temperature superconductors.
• This method provides a reliable approach for characterizing thin-film materials at low temperatures.