Meaning
Analytical procedures using scanning transmission electron microscopy and energy dispersive spectroscopy measure the chemical changes at the interfaces between different crystal grains. High resolution stem eds boundary profiling allows researchers to detect the segregation of single layers of atoms that could embrittle a metal. This technique is the most precise way to characterize the chemistry of internal surfaces.
Beam Interaction
Focused electrons pass through a thin foil sample to generate x-rays that are characteristic of the elements present at each point. In stem eds boundary profiling the beam moves across the interface in small steps to create a plot of concentration versus distance. The quality of the data depends on the beam being perfectly aligned with the grain boundary plane.
Data Resolution
Accuracy at the atomic scale requires a stable environment free from vibration and electromagnetic interference. Modern stem eds boundary profiling can resolve chemical differences over a distance of less than one nanometer. This level of detail is necessary for understanding how dopants influence the electrical properties of semiconductor devices.
Sample Preparation
Creating a specimen that is thin enough for electron transmission without introducing artificial defects is a major challenge. Standard stem eds boundary profiling uses focused ion beam milling to extract a tiny wedge of material from a specific location on a part. The thickness of this wedge must be uniform to ensure that the chemical readings are not distorted by varying path lengths.
This careful preparation is the most time consuming part of the entire analysis.
