Specific Process Knowledge/Characterization/Element analysis

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Element analysis at Nanolab

The following techniques for elemental analysis are available at Nanolab.

• EDX
• SIMS (no longer available at Nanolab, SIMS service can be provided by this company: [1])
• XPS (ESCA)

In the table below the three techniques are compared

Comparison of EDX, SIMS and XPS

	SEM with EDX	Atomika SIMS	XPS (or ESCA)
Full name	Energy Dispersive X-ray Analysis	Secondary Ion Mass Spectroscopy	X-ray Photoelectron Spectroscopy (or Electron Spectroscopy for Chemical Analysis)
Technique	The primary beam of high energy electrons used in the SEM for imaging impinges on the sample atoms and leaves them in an excited state. X-rays with a characteristic energy are generated in the relaxation process. The combination of the fine control of the primary beam offered by the SEM and the detection of the X-rays makes it possible to make point-like elemental analysis.	A beam of high energy ions (cesium or oxygen) is used for sputtering off surface atoms of the sample. The material coming off the sample in this process is analysed with a mass spectrometer.	In a process in which a monochromatic beam of X-rays irradiates the sample surface, electrons bound inside the sample are knocked free to become photoelectrons. Escaping the sample with characteristic energy, these electrons not only carry elemental information but also chemical information. Analysing them respect to energy and numbers and adding an ion gun for depth profiles provide a powerful analysis tool.
What elements are detected	Every element heavier than boron/carbon	In principle every element, however, the sensitivity	Every element except hydrogen and helium.
Chemical information	None	None	Chemical state information
Sample requirements	Vacuum compatible	UHV vacuum compatible The sample needs to be cut into small (app. 5*5 mm) pieces.	UHV vacuum compatible Sample size max 50x50 mm, thickness max 20 mm.
Spatial resolution	Very precise point-like analysis is possible with SEM electron beam.	A square with dimensions of a few hundred microns is selected for analyis with a camera	Using a magnified view from a camera, a point that covers an area down to an ellipse of 40 microns may be irradiated with photons (the default size is 400 microns)
Depth resolution	The size of the interaction volume depends on the high voltage in the SEM and the sample density: The higher the SEM high voltage the bigger and deeper the interaction volume. The more dense the material is the smaller is the interaction volume. See section 'Spatial resolution using EDX' below.	The sputtering of the surface makes it possible to perform detailed depth profiling with extremely good sensitivity and depth resolution.	Very surface sensitive technique. Only photoelectrons from the top layer (a few nanometers deep) escape unscattered. By using the ion beam etch, the composition of deeper lying layers can be probed.
Detection limit	Approximately 1 % atomic weight	Down to 1 ppb for certain elements	Approximately 1 % atomic weight
Speed of measurement	Very fast and easy	Time consuming	Quite fast and easy