Specific Process Knowledge/Characterization/Element analysis: Difference between revisions
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== Spatial resolution using EDX == | == Spatial resolution using EDX == | ||
Using | Using the the very fine beam of electrons from a SEM one is capable of making point-like elemental analysis of the sample. A multiple scattering process will occur when the incident electrons collide with the sample electrons. This process generates low energetic secondary electrons and it continues until the incident electrons have lost so much energy that they are not different from the secondary electrons. The volume of the sample in which this process takes place is called the interaction volume. X-rays are generated throughout the interaction volume and we are therefore probing the whole volume when using the EDX detector. | ||
The | |||
Using some empirical equations one can calculate how the distribution of X-rays generated in the sample will be at certain high voltages. Below are shown the depth profiles of X-rays from silicon and gold when irradiated with 5-30 kV electrons. | |||
<gallery caption="Curves that show the depth of origin of the X-rays" | <gallery caption="Curves that show the depth of origin of the X-rays" | ||
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image:AuX-rayemission.jpg|The depth profiles of X-rays emerging from bulk gold at different high voltages. | image:AuX-rayemission.jpg|The depth profiles of X-rays emerging from bulk gold at different high voltages. | ||
</gallery> | </gallery> | ||
It is seen that the trend is: | |||
* Increasing the high voltage gives rise to a bigger and deeper interaction volume and hence increases the depth which is probed. | |||
* Increasing the density of the sample material reduces the size and depth of the interaction volume - hence a more shallow layer is probed. | |||