Local structure and defects in ion irradiated KTaO₃

Area of Science:

• Materials Science
• Solid State Physics
• Ion Beam Modification

Background:

• Cubic perovskite Potassium Tantalate (KTaO3) is a material with significant dielectric properties.
• Understanding structural modifications under ion irradiation is crucial for its applications in electronics and radiation environments.

Purpose of the Study:

• To investigate the local structural modifications in KTaO3 induced by different energies of Au ion irradiation.
• To elucidate the defect formation mechanisms and their evolution under irradiation.

Main Methods:

• Raman Spectroscopy
• X-ray Absorption Spectroscopy (XAS) at Ta L3-edge
• Extended X-ray Absorption Fine Structure (EXAFS)
• Density Functional Theory (DFT) calculations

Main Results:

• Irradiation with 3 MeV Au ions, dominated by displacement cascades, leads to the splitting of Ta-O bonds in TaO6 octahedra, indicating the formation of Ta antisite defects (TaK) coupled with oxygen vacancies (VO).
• High-energy (1.1 GeV) Au ion irradiation, characterized by intense ionization, causes a blue shift and intensity reduction in Raman spectra.
• Sequential irradiation shows a decrease in the concentration of coupled TaK-VO defects upon subsequent 1.1 GeV Au ion irradiation.

Conclusions:

• The study identifies distinct defect structures formed by different irradiation regimes in KTaO3.
• The findings highlight the interplay between displacement damage and electronic excitation in modifying perovskite structures.