Specimen-thickness effects on transmission Kikuchi patterns in the scanning electron microscope.

Area of Science:

• Materials Science
• Electron Microscopy
• Crystallography

Background:

• Transmission Kikuchi diffraction (TKD) is a powerful technique for analyzing crystalline materials.
• Understanding the influence of sample properties on TKD pattern quality is crucial for accurate microstructural analysis.

Purpose of the Study:

• To investigate the effect of specimen thickness on the generation of transmission Kikuchi patterns.
• To determine the optimal thickness range for obtaining high-quality TKD patterns for automated indexing.
• To identify the regions within a sample where electron scattering events are most likely to contribute to detectable transmission patterns.

Main Methods:

• Experiments were conducted using a scanning electron microscope (SEM).
• Specimens of varying thicknesses were prepared from materials including hafnium dioxide and aluminum.
• Monte Carlo simulations were employed to model electron scattering and transmission through the specimens.

Main Results:

• High-quality transmission Kikuchi patterns, suitable for automated indexing, were obtained from films spanning nearly three orders of magnitude in thickness (5 nm to 3 μm).
• This thickness range corresponds to a mass-thickness range of approximately 5 to 810 μg cm⁻².
• Analysis indicated that the most significant scattering events contributing to detectable transmission patterns occur very close to the exit surface of the specimen.

Conclusions:

• Specimen thickness has a demonstrable effect on transmission Kikuchi pattern generation.
• Automated indexing of TKD patterns is feasible across a broad range of specimen thicknesses.
• The findings provide valuable insights for optimizing sample preparation and data acquisition in TKD analysis.