Challenges of Electron Correlation Microscopy on Amorphous Silicon and Amorphous Germanium
Dražen Radić1, Martin Peterlechner1, Katharina Spangenberg1
1Institute of Materials Physics, University of Münster, Wilhelm-Klemm-Str. 10, Münster, 48149 North Rhine-Westphalia, Germany.
Summary
Electron correlation microscopy of amorphous germanium and silicon revealed significant experimental artifacts. The study concluded that structural changes were primarily electron beam-driven, not due to self-diffusion at accessible temperatures.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Electron Microscopy
Background:
- Studying self-diffusion in amorphous materials like germanium (a-Ge) and silicon (a-Si) is crucial for understanding their properties.
- Electron correlation microscopy offers a potential avenue for investigating atomic-level dynamics.
Purpose of the Study:
- To investigate self-diffusion in amorphous germanium and silicon using electron correlation microscopy.
- To identify and mitigate experimental artifacts affecting in situ measurements.
Main Methods:
- Acquisition of tilted dark-field images during in situ heating in a transmission electron microscope.
- Analysis of intensity autocorrelation data using stretched exponential fits to determine characteristic times (τKWW).
Main Results:
- Measurements were significantly impacted by artifacts including contamination, crystallization, sputtering, and sample bending.
- The characteristic times (τKWW) exhibited spatial heterogeneity, potentially due to nonergodicity, artifacts, or structural inhomogeneity.
- Characteristic times were largely temperature-independent, particularly for amorphous germanium.
Conclusions:
- Experimental artifacts severely limit the study of self-diffusion in amorphous germanium and silicon via this method.
- Observed structural rearrangements are predominantly driven by the electron beam.
- True diffusive dynamics are too slow to be measured at the employed annealing temperatures.
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