How to Read an X-ray Photoelectron Spectrum
If yous've ever sent a sample in for surface analysis, at that place'south a skilful take a chance that you're already familiar with x-ray photoelectron spectroscopy (XPS). XPS assay is a widely used surface analysis technique, with applications across numerous industries.
As well referred to equally electron spectroscopy for chemical analysis (ESCA), XPS is suitable for a broad range of materials, and tin can provide valuable information most the elemental and binding energy of a material's surfaces and interfaces.
Of class, XPS survey scans aren't exactly self-explanatory. What exercise all those peaks and jagged lines mean? When you work with Innovatech Labs, you'll receive detailed insights and actionable recommendations in an like shooting fish in a barrel-to-empathise format.
And for those of you lot who'd like to dig in and truly empathise the data and what the results mean, we take developed this introduction to analyzing and interpreting XPS information.
The Analysis
In gild to translate XPS or ESCA results, it's helpful to understand how this technique actually works. Just put, XPS uses an x-ray beam to excite atoms on the surface of a solid sample, which spurs the release of photoelectrons. From there, the kinetic free energy and the number of electrons that escape from the superlative 0 to ten nanometers of the sample are measured.
To dive a little deeper, each atom in a fabric contains core electrons. When the x-ray beam hits the surface of the material, the energy from the x-ray is absorbed by one of the core electrons. The free energy needed to cause the cadre electron to exist emitted and subsequently detected is unique to each element. This uniqueness allows the apply of binding energy to place the elements present on the surface of the analyzed fabric.
Because XPS just detects electrons that escape from the sample and reach the detector, the elemental signals from the surface are much stronger than from those deeper in the sample. In addition, the binding energy changes with the chemical environment of the chemical element, causing an effect is known as "chemical shift." As a result, XPS can estimate the thickness, uniformity, and surface chemical science of the sample'southward surface, coatings, and films.
XPS detects all elements besides hydrogen and helium, so a survey scan is unremarkably a starting point for near analyses. For each element, there is a range of electron states open to excitation past the x-ray axle. Seeing the total range of elements present in the sample'southward surface makes information technology easier to zero in on specific XPS spectra in subsequent loftier-resolution testing.
How to Clarify XPS Spectra Information
XPS analysis is rooted in understanding the position and intensity of peaks on the survey scans and the high-resolution spectra data. And so, when it comes to XPS data interpretation, hither'due south what y'all need to know.
The X-Centrality: Summit Position
In XPS analysis, the position of a peak on the x-axis indicates the elemental and chemical composition. This centrality is traditionally displayed equally "Binding Energy" in electron volts (eV).
The binding energy is calculated from the difference in the energy of the x-ray source and the kinetic free energy of the photoelectron being detected. Traditionally, the x-axis is plotted from the highest to lowest binding energy, which is opposite of what you might look. If information technology were to be plotted every bit the photoelectron energy, and so the x-centrality would go from zilch eV to the highest photoelectron energy.
The Y-Axis: Peak Intensity
The y-axis in XPS analysis records the intensity of surface material—how much of a item element can be institute at the surface. This axis usually displays the total number of photoelectron counts per 2d.
Typically, conquering of the photoelectron intensity versus binding free energy from effectually ane,200 eV to zero eV is called a survey scan.
Overlapping Peaks
Like life, XPS results can sometimes be a little messy. Sometimes there won't be conspicuously resolved peaks on the ten-centrality. For instance, a sample with both tin and lead might take interfering peaks. Innovatech Labs uses peak models to split elemental information for further analysis.
More than than One Elemental Peak
In some cases, elements accept more than one transition that is suitable for quantification. For instance, a scan of your sample may include ii notable peaks for silicon (due east.1000., Si 2s and Si 2p). To positively place an element, information technology's important that all of its transitions exist present in the survey scan and show approximately the correct ratio in their intensity.
Withal, only one transition can be used in analysis. In this case, it's of import to utilise the transition that has the largest peak. This minimizes the risk that smaller peaks will interfere with the analysis.
Examples of Analyzing and Interpreting XPS Data
At present that y'all sympathise the basics of how to read XPS spectra data, below we share some examples of diverse testing results.
Analysis of Haze on a Polyimide Substrate
When an electronics manufacturer observed a haze on a polyimide moving-picture show, they suspected chromium residuum resulting from a chromium motion picture non being completely etched during the production.
XPS testing produced the following testing survey browse of the hazed area. The survey scan shows the presence of chromium (C1s) in the hazed area, indicating that the chromium film was not completely removed.
Passivation Integrity of Stainless Steel
A manufacturing client wanted to ensure that a stainless steel passivation layer was sufficient for rust prevention. Our team turned to XPS assay for quantitative measurement of surface impurities in the oxide layers and to provide information about the oxidation country of chromium and iron. We were able to discern the chromium-to-iron ratio is ii.four and meets scientific requirements for rust prevention.
Desire to Learn More About X-Ray Photoelectron Spectroscopy?
XPS analysis is a bang-up starting signal for a wide range of applications in manufacturing and quality control. If surface chemistry is critical for product function and safety, XPS might be the test for you lot. Innovatech Labs is eager to field any of your questions about XPS or other materials analysis.
Contact united states today for more than data. You can likewise request a quote if y'all accept a specific project in mind.
Source: https://www.innovatechlabs.com/newsroom/2075/how-analyze-xps-data/
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