XPS/ESCA (X-ray Photoelectron Spectroscopy/Electron Spectroscopy for Chemical Analysis )
X-ray Photoelectron Spectroscopy/Electron Spectroscopy for Chemical Analysis (XPS/ESCA)
X-ray Photoelectron Spectroscopy (XPS), also known as Electron Spectroscopy for Chemical Analysis (ESCA), 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 50-70 Angstroms. Alternatively, XPS can be utilized for sputter depth profiling to characterize thin films by quantifying matrix-level elements as a function of depth. XPS is an elemental analysis technique that is unique in providing chemical state information of the detected elements, such as distinguishing between sulfate and sulfide forms of the element sulfur. The process works by irradiating a sample with monochromatic x-rays, resulting in the emission of photoelectrons whose energies are characteristic of the elements within the sampling volume.
Main applications
- 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
- Measuring lube thickness on hard disks
- Obtaining depth profiles of thin film stacks (both conducting and non-conducting) for matrix level constituents
- Assessing the differences in oxide thickness between samples
XPS/
Technical Capabilities
Signal Detected:
Photoelectrons from near surface atoms
Elements Detected:
Li-U Chemical bonding information
Detection Limits:
0.01 - 1 at% sub-monolayer
Depth Resolution:
20 - 200 Angstroms (Profiling Mode)
10 - 100 Angstroms (Surface analysis)
Imaging/Mapping:
Yes
Lateral Resolution/Probe Size:
10 µm - 2 mm
Ideal Uses for XPS Analysis
- Surface analysis of organic and inorganic materials, stains, or residues
- Determining composition and chemical state information from surfaces
- Depth profiling for thin film composition
- Silicon oxynitride thickness and dose measurements
- Thin film oxide thickness measurements (SiO2, Al2O3 etc.)
Relevant Industries for XPS Analysis
- Aerospace
- Automotive
- Biomedical/biotechnology
- Compound Semiconductor
- Data Storage
- Defense
- Displays
- Electronics
- Industrial Products
- Lighting
- Pharmaceutical
- Photonics
- Polymer
- Semiconductor
- Solar Photovoltaics
- Telecommunications
Strengths of XPS Analysis
- 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 (paper, plastics, and glass)
- Depth profiling with matrix-level concentrations
- Oxide thickness measurements
Limitations of XPS Analysis
- Detection limits typically ~ 0.1 at%
- Smallest analytical area ~10 µm
- Limited specific organic information
- Sample compatibility with UHV environment