X-Ray Photoelectron Spectroscopy (XPS) is the ideal technique to use if you need a quantitative analysis of the surface (top 5-7 nanometers) of your sample. XPS can also give you information about the chemical bonding on the surface of your sample. For example, one can observe different bonding states of C in polymeric materials.
How XPS works — the sample is bombarded with an x-ray beam causing photoelectrons to be emitted from the surface. The energy of these photoelectrons is characteristic of the elemental composition of your sample.
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Instrumentation Available
Key Attributes
- Elements detected: Li-U
- Detection limits: 0.01 – 1% atomic (depending on sample and element)
- Imaging: Yes
- Lateral resolution 10 µm to 2 mm (depending on instrument)
- Surface sensitivity: top 1 – 10 nm
- Depth profiling: Yes, both elemental and molecular (with gas cluster ion bombardment)
Strengths
- Sensitive to differences in chemical environment
- Very surface sensitive (top 1 – 10 nm)
- Quantitative without standards
- Straightforward analysis of insulating samples (polymers, plastic, glass, etc.)
- Quantitative depth profiling on a wide range of materials
Limitations
- Detection limits ~ 0.1 at%
- Hydrogen is not detectable
- Poor lateral resolution ~30 µm
- Sample must be UHV (<1e-9 torr) compatible
- For organic bonding analysis, you must have some understanding of your sample
Applications
- Identification of unknown discolorations, hazes and stains
- Compositional analysis of powders and debris
- Identification of surface contamination
- Identification of changes in polymer functionality as a function of treatment
- Compositional depth profiling of thin films stacks (both elemental and molecular)
- Measurement of the oxide thickness on different samples
Additional Reading
