Assessing electron beam sensitivity for SrTiO3 and La0.7Sr0.3MnO3 using electron energy loss spectroscopy

Area of Science:

• Materials Science
• Solid State Physics
• Electron Microscopy

Background:

• Electron beam irradiation can induce damage in materials during microscopy.
• Understanding beam damage thresholds is crucial for accurate material characterization.
• Aberration-corrected scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) are powerful techniques for nanoscale analysis.

Purpose of the Study:

• To determine the thresholds for electron beam damage in La0.7Sr0.3MnO3 and SrTiO3.
• To evaluate the effectiveness of STEM imaging versus EELS for detecting beam damage.
• To assess the influence of acceleration voltage, probe current, and exposure time on material damage.

Main Methods:

• Materials (La0.7Sr0.3MnO3 and SrTiO3) were subjected to intense electron probe exposure using STEM.
• Simultaneous EELS data acquisition was performed during electron beam irradiation.
• Electron beam damage was quantified by analyzing changes in core loss fine structure using a refined model-based approach.

Main Results:

• SrTiO3 showed beam damage at 200kV (detected by EELS and STEM contrast), but not at 80kV.
• La0.7Sr0.3MnO3 exhibited beam damage at both 80kV and 200kV, detectable by EELS but not STEM contrast.
• STEM image contrast changes due to minor damage can be difficult to discern under common experimental conditions.

Conclusions:

• EELS is a more sensitive technique than STEM imaging for detecting early-stage electron beam damage in these materials.
• The common practice of comparing pre- and post-acquisition STEM images may lead to misinterpretation of beam damage as genuine material property changes.
• Lower acceleration voltages (e.g., 80kV) can mitigate beam damage in certain materials like SrTiO3.