Nanostructures evolution assessment and spectroscopic properties modification induced by electronic energy loss in KTaO₃ crystal

Highlights

• Depth-dependent Raman spectra clarify the lattice distortion and symmetry degeneration along the ion penetration path.

• The track fine structures are demonstrated by experimental observations and MD simulations combined with iTS calculations.

• A quantitative relationship is successfully established to predict the track fine structures under various irradiation conditions.

• Nano-hillocks and nano-pits are obtained under the combined action of kinetic and potential energy depositions.

• Suppressed fluorescence emission and enhanced photoconductivity performance are achieved.

Abstract

Modifications of micro/nanostructure and photoelectric properties under swift ion irradiation (645 MeV Xe³⁵⁺) of KTaO₃ crystal with varying electronic energy losses (7.2–31.4 keV/nm) and ion velocities (0.18–5.00 MeV/u) have been studied by combining experimental and calculated approaches. The i-TS calculations combined with molecular dynamics simulations are compared with the experimental observations, revealing the inner track fine structures from individual spherical defects to continuous ion tracks with core–shell morphologies, and a quantitative relationship, including the melting (0.42 eV/atom), damage (0.75 eV/atom), and amorphous (1.71 eV/atom) thresholds, is established to successfully predict the inner disorder/amorphous proportions and track damage morphologies. The surface nanostructures of nanohillocks (isolated or partial overlaps) and nanopits (serious overlaps) directly depend on the combined action of the deposited potential and kinetic energies of incident ions, which induce local melting and sublimation in the near-surface region. Owing to the decreased recombination and the increased separation efficiency between electrons and holes, the higher photogenerated charge carrier mobility enhanced the photocurrent effect, further optimizing the photoconductivity performance in Xe³⁵⁺-irradiated KTaO₃. Therefore, controlled defect engineering using the ion irradiation technique, as an effective strategy, could design tailored nanostructure systems and regulate photoelectric properties, further promoting the development of novel technological applications.