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X-ray photoelectron spectroscopy (XPS) KRATOS Analytical AxisUltra
Surface analysis of materials
X-ray photoelectron spectroscopy (XPS) is a surface analysis technique used to characterize a wide variety of materials, including inorganic and organic compounds, semiconductors, natural materials such as lignocellulose, and synthetic materials such as meso- and microporous ceramics. The sample surface is irradiated with an X-ray beam, and the kinetic energy of the emitted photoelectrons is measured. The analysis generally probes the first few nanometres of the surface (10 nm). XPS determines the elemental composition of the surface, the relative abundance of the detected elements by semi-quantitative analysis, and their chemical environment and oxidation state. The precision of this last determination depends in particular on the concentration of the species, the spectral resolution and the chemical complexity of the sample. All elements of the periodic table (Li–U) can be detected, with the exception of hydrogen and helium.
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Availability and contact
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User Fees
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Sample types
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Technique and applications
X-ray photoelectron spectroscopy (XPS) is a surface chemical analysis technique based on the photoelectric effect. It makes it possible to identify the elements present in the outermost layers of a material, estimate their relative atomic concentrations and determine their chemical environment. XPS is particularly sensitive to oxidation states, chemical bonding, contaminants, surface treatments and shallow interfaces. In most materials, the analytical information comes mainly from the first few nanometres, even though the X-rays penetrate much deeper.
1 | X-ray Generation
In a conventional XPS source, electrons emitted by a cathode are accelerated toward a metal anode. Their interaction with the anode produces continuous braking radiation (Bremsstrahlung) and characteristic X-ray lines. The most common sources use the Al Kα line, with a nominal energy of about 1486.6 eV, and the Mg Kα line, at about 1253.6 eV. The aluminium and magnesium components should therefore be referred to as anodes or targets, not cathodes.
A monochromatic source uses a crystal to select a narrow band around a characteristic line, most often Al Kα. Monochromatization reduces the energy width of the incident radiation, removes much of the continuum and satellite lines, and thus improves energy resolution. This improvement is essential when several chemical states produce peaks separated by only a few tenths of an electronvolt.
The irradiated area and the area actually analyzed are not necessarily the same. Lateral resolution depends on both the size of the X-ray beam and the field of view accepted by the electron optics. Depending on the configuration, the instrument can acquire spot spectra, analyze small areas or reconstruct chemical images. It is therefore important to compare the analysis area with the actual size of the phases, defects or contaminants being studied.
Technique and applications
Sample types
Types and dimensions
Accepted solids include powders, films, inorganic compounds, alloys, semiconductors, polymers, catalysts, glasses, ceramics, wood, and biomaterials. The usual maximum size is 20 × 70 mm and the thickness up to 5 mm; thicker samples may be evaluated.
Ultra-high vacuum compatibility
Samples must be stable at a pressure below 10⁻⁹ Torr, dry, and have low outgassing properties. Volatile, moist, porous, or high specific surface area materials require evaluation and sometimes longer pumping times.
Preservation and handling
Surfaces are generally analyzed as is to avoid chemical treatment leaving residues or altering the condition being studied. Use powder-free gloves, clean tweezers, and clean containers. Never touch the area being analyzed. Powders must be immobilized according to an approved protocol.
Impact of preparation on quality and repeatability
Because XPS probes only a few nanometers, a very thin layer of grease, oil, silicone, dust, adventitious oxide, or solvent residue can dominate the signal. Different handling procedures can therefore create larger discrepancies than those due to the material itself. Outgassing degrades the vacuum, increases the background, and can delay or prevent analysis. Minimal but rigorously clean preparation, proper conditioning, and a documented surface history are essential for repeatability and accurate assignment of chemical states.
COMPATIBLE SAMPLES
Sample types
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User Fees
MicroLab rates are set according to the type of user, the instrument usage mode and, depending on the service, the analysis time or the number of samples. Some services, particularly sample preparation, may be billed per sample, while instrument use and data processing are generally billed on an hourly or daily basis.
User Categories
Université Laval
This category includes users whose projects are funded, in whole or in part, by Université Laval, regardless of their faculty or affiliated unit. In particular, it includes undergraduate, master’s and doctoral students carrying out work as part of a research project supervised by a Université Laval professor or researcher.
Research / Public Funding
This category includes students, professors, researchers and professionals from other Canadian universities, CEGEPs or research centres, when the work is carried out as part of projects or within institutions funded primarily by public funds. These funds may come, for example, from government or para-governmental organizations, federal or provincial research programs, or other public funding sources.
Industry
This category applies to private companies and to work carried out in an industrial or commercial context.
Usage Modes
When several usage modes are offered for an instrument, rates distinguish between assisted and unassisted use.
Assisted
The instrument is operated by the lead operator or the technical manager, who is responsible for starting the analysis, changing samples when necessary and assisting the user through the various stages of the measurement. This mode is particularly suited to analyses requiring specific instrumental expertise and to occasional users.
Unassisted
After completing appropriate training, users can carry out their own analyses and, when necessary, change samples themselves. Use nevertheless remains under the supervision of the instrument manager. Initial training is billed according to the time required and includes both staff time and instrument use.
Unassisted use is restricted to Université Laval users and depends on the instrument, the type of analysis and the user's level of experience. For the conditions of access to this mode, please contact the manager of the relevant instrument.
Pricing Based on Analysis Duration
For services with hourly and daily rates, billing is based on the total instrument usage time, including the time required to prepare and configure the instrument for the analysis.
For periods under 6 hours, the hourly rate applies. From 6 hours up to 24 hours, a daily flat rate applies. Beyond 24 hours, billing continues in daily increments at the applicable daily rate.
The daily flat rate is particularly advantageous for long analyses: its cost generally corresponds to that of six hours of use, while allowing the instrument to be used for up to 24 hours. It thus prevents costs from rising continuously during extended acquisitions and makes it easier to budget for an analysis session. For example, an analysis lasting 12, 18 or 24 hours is billed at the same daily flat rate rather than as the sum of the individual hours.
Services listed “per sample” are billed according to the number of samples processed, regardless of this hourly/daily structure.