Meaning
Analytical techniques use a beam of electrons passed through an ultra-thin specimen to create a high-resolution image of its internal structure. This transmission electron microscopy provides a level of detail that is thousands of times greater than what a light microscope can achieve. The resulting data shows the arrangement of atoms and the presence of crystal defects within a material.
Specimen Preparation
Creating samples that are thin enough for electrons to penetrate is a complex and time-consuming process. Samples used in transmission electron microscopy are often less than one hundred nanometers thick and are prepared using ion milling or ultramicrotomy. If the sample is too thick, the beam is absorbed rather than transmitted, which results in a dark and useless image.
This stage is often the bottleneck in a failure analysis laboratory.
Contrast Mechanism
Differences in the atomic weight and thickness of the sample create the variations in the image that reveal the microstructure. When electrons interact with the sample, they are scattered by the nuclei, which produces diffraction patterns. These patterns allow researchers to identify the phase and orientation of the crystals.
Material Characterization
High-end manufacturing relies on this technology to verify the quality of nano-scale features in semiconductors and catalysts. Using transmission electron microscopy ensures that the grain boundaries and interfaces meet the design specifications for a production run.
