X-ray Photoelectron Spectroscopy (XPS Spectroscopy) or Electron Spectroscopy for Chemical Analysis (ESCA)

X-Ray Photoelectron Spectroscopy (XPS Spectroscopy) is also known as Electron Spectroscopy for Chemical Analysis (ESCA). X-Ray Photoelectron Spectroscopy is used to determine quantitative atomic composition and chemistry. It is a surface analysis technique with a sampling volume that extends from the surface to a depth of approximately 50-100 Å. XPS Spectroscopy can also be used for sputter depth profiling. This is useful to characterize thin films by quantifying matrix-level elements as a function of depth.

XPS Spectroscopy is an elemental analysis technique. This is unique in also providing chemical state information for the detected elements. A good use is distinguishing between sulfate and sulfide forms of sulfur. The process works by irradiating a sample with monochromatic X-rays. This results in the emission of photoelectrons whose energies are characteristic of the elements within the sampling volume.

SMART chart

XPS Spectroscopy is part of our Smart Chart Series. XPS Spectroscopy can detect and quantify all elements except for H and He and provide chemical state information, making it a powerful survey analysis technique.

X-rays penetrate a sample several microns deep and force electrons from the sample. Therefore, only electrons from the top 100 Armstrong’s have enough energy to reach the XPS detector.

Firstly, XPS Spectroscopy usually starts with a survey that looks at the full energy range scan at highest sensitivity. Therefore, we can identify and quantifies elements at surface. Secondly, we typically use high resolution XPS analysis to determine the bonding state where we use narrow scans at higher energy resolution. This can determine the chemical bonding state from peak position and peak shape. Finally, to determine a thin film composition, depth profile analysis is useful, as it looks at atomic composition.

EAG uses X-ray Photoelectron Spectroscopy in a variety of applications to help customers across a range of industries. For instance, with R&D, process development/improvement and failure analysis.

XPS Spectroscopy Examples

Examples of XPS Analysis include:

Identifying stains and discolorations
Characterizing cleaning processes
Analyzing the composition of powders and debris
Determining contaminant sources
Examining polymer functionality before and after processing to identify and quantify surface changes
Obtaining depth profiles of thin film stacks (both conducting and non-conducting) for matrix level constituents and contaminants (down to the low % level)
Assessing the differences in oxide thickness between samples
Measuring lubricant thickness on hard disks

XPS Spectroscopy Summary

Ideal Uses

Firstly, surface analysis of organic and inorganic materials, stains, or residues
Secondly, determining composition and chemical state information from surfaces
Thirdly, depth profiling for thin film composition
In addition, thin film oxide thickness measurements (SiO₂, Al₂O₃)

XPS Strengths

Chemical state identification on surfaces
Identification of all elements except for H and He
Quantitative analysis, including chemical state differences between samples
Applicable for a wide variety of materials, including insulating samples (including paper, plastics and glass)
Depth profiling with matrix-level concentrations
Oxide thickness measurements

XPS Limitations

Firstly, detection limits typically ~ 0.1 at%
Secondly, smallest analytical area ~10 µm
In addition, limited specific organic information
Lastly, sample compatibility with UHV environment

XPS Spectroscopy Technical Specifications

Signal Detected: Photoelectrons from near surface atoms
Elements Detected: Li-U Chemical bonding information
Detection Limits: 0.1–1 at% sub-monolayer
Depth Resolution: 20–200 Å (Profiling Mode); 10–100 Å (Surface analysis)
Imaging/Mapping: Yes
Lateral Resolution/Probe Size: 10 µm – 2 mm

Above all, XPS Spectroscopy insights into a sample’s chemical makeup allow you to make product and process improvements more quickly, enabling you to reduce cycle time and save money.

In addition, with EAG, you also have access to the best facilities, instruments and scientists available for performing XPS Spectroscopy analyses. We handle many different materials from multiple industries, giving us a very wide range of experience. Lastly, our person-to-person service ensures that you will receive answers to all of your questions.