X-ray Photoelectron Spectroscopy – XPS

X-ray Photoelectron Spectroscopy

X-ray photoelectron spectroscopy (XPS) is a surface-sensitive elemental analysis technique. It is a powerful tool for determining the elemental and chemical state information of specimen surfaces. Combined with ion milling, XPS can be applied to depth profiling of thin films, detecting surface contamination of materials, inspecting surface treatments, and other surface characterization in the nanoscale. Its applicability in material characterization is far-reaching from inorganic compounds, metal alloys, polymers, glasses, biomaterials, ion modified materials, coatings, ceramics to semiconductors, etc.

In XPS, a sample is irradiated with the monochromatic x-rays that result in the emission of inner orbital and bonding electrons. The measurement of these electrons binding energies and intensities (from the top 1–10 nm of the sample) allows identification and quantification of the elements on the material’s surface.

X-ray Photoelectron Spectroscopy (XPS) Common Uses

• Determination of the empirical formula of pure materials
• Distinguishing between sulfide and sulfate forms of a sulfur element
• Analysis of the surface composition of fiber-reinforced composite materials
• Quantitative information about graphene, such as the number of layers and identification of impurities
• Determining the differences in oxide layer (SiON, SiO2) thickness between samples
• Quantitative analysis of surface layers generated during the wear process
• Chemical analysis of plasma-treated textiles
• Analysis of stainless steel passivation by determining the corrosion, adhesion, and friction properties
• Investigation of the extent of functionality and specific adsorption or binding of the biomolecules (proteins, enzymes, lipids) onto the various surfaces

Advantages

• An effective technique for both conductive and insulating samples
• Provides extensive information such as surface sensitivity; quantifiable elemental and chemical details2
• Ability to perform depth profiling by quantifying matrix-level elements as a function of depth
• Ability to distinguish between oxidations states of the molecules

Limitations

• Samples should be compatible with an ultra-high vacuum (UHV) environment; unsuitable for biological samples
• Detection of all elements except H and He
• Identification of the elemental composition in ~ 0.1 atomic percent or 1000ppm
• Typically, the smallest analytical area is ~10 µm
• The low resolution of source radiation (~0.1 – 1.0 eV)
• Many potential artifacts may arise that are often related to the sample preparation
• It takes a long time (½ to 8 hours per sample) to obtain the XPS spectrum

Industries

• Semiconductors
• Electronics
• Chemical Industry
• Thin Films and Coatings
• Tribology
• Advanced Materials
• Biotechnology
• Metal/Steel Industry
• Fiber Composites

X-ray Photoelectron Spectroscopy (XPS) Laboratories

• EAG Laboratories, Inc.
• Intertek
• Cerium Laboratories, LLC
• Jordi Labs
• Innovatech Labs
• Nanolab Technologies, Inc.
• Lucideon Group
• Micron Inc. Analytical Service Laboratory
• Rocky Mountain Laboratories, Inc.

More Details

• Working principle of XPS
• Limitations of XPS