Precession electron diffraction tomography on twinned crystals: application to CaTiO₃thin films

Abstract

Strain engineering via epitaxial thin‐film synthesis is an efficient way to modify the crystal structure of a material in order to induce new features or improve existing properties. One of the challenges in this approach is to quantify structural changes occurring in these films. While X‐ray diffraction is the most widely used technique for obtaining accurate structural information from bulk materials, severe limitations appear in the case of epitaxial thin films. This past decade, precession electron diffraction tomography has emerged as a relevant technique for the structural characterization of nano‐sized materials. While its usefulness has already been demonstrated for solving the unknown structure of materials deposited in the form of thin films, the frequent existence of orientation variants within the film introduces a severe bias in the structure refinement, even when using the dynamical diffraction theory to calculate diffracted intensities. This is illustrated here using CaTiO3 films deposited on SrTiO3 substrates as a case study. By taking into account twinning in the structural analysis, it is shown that the structure of the CaTiO3 films can be refined with an accuracy comparable to that obtained by dynamical refinement from non‐twinned data. The introduction of the possibility to handle twin data sets is undoubtedly a valuable add‐on and, notably, paves the way for a successful use of precession electron diffraction tomography for accurate structural analyses of thin films.

3D Electron Diffraction: The Nanocrystallography Revolution

“…125 A very promising application of dynamical refinements is foreseen for such cases where the main goal is to point out subtle structural changes. Steciuk et al 76 showed that the structure of a thin film of CaTiO 3 grown on SrTiO 3 can be refined even in the presence of twinning and that the evolution of the thin film structure as a function of the distance from the substrate may also be observed.…”

“…Since 2007, the three-dimensional ED method has spread with an exponential trend. Very soon, still in the hand of few specialists, it allowed the structure determination of landmark samples, mostly inorganic, that were considered impracticable for X-ray methods. − Later, the introduction of ultrafast data acquisition procedures and of more sensitive detectors allowed establishing robust experimental protocols also for organic and metalorganic materials. − Finally, three-dimensional ED found successful applications for macromolecules − and other structures of biologic interest. − The growing attention on three-dimensional ED is confirmed by the number and impact of related publications in the very last year, − and by the fact that this method has been considered one of the most important recent scientific breakthroughs …”

Oxygen crystallographic positions in thin films by non-destructive resonant elastic X-ray scattering

“…A possibility for such systems is precession electron diffraction, a technique coupled with transmission electron microscopy which allows solving the structure of thin-film materials (Steciuk et al, 2019;Rotella et al, 2015). Despite its potency in obtaining accurate structure models, this technique requires a tedious and destructive sample preparation process.…”

Phosphinate MOF formed from tetratopic ligands as proton conductive materials

“…In the hkl reciprocal space sections, the diffraction data showed a mirror symmetry (Figure S10), which is incompatible with the structure model. All measured diffraction data showed the same twinning, which was used during the dynamical refinement [29]. Similarly to the ICR-10 structure, the atomic displacement parameters of the two ligand legs pointing towards the pores were substantially higher than those of the rest of the structure.…”