The photoelectrons of interest have relatively low kinetic energy. All elements, except hydrogen and helium, are detected. Detection limits are approximately 0. High Resolution Multiplex Scan - This technique evaluates the chemical state s of each element through its core electron binding energies.
Precise determinations of binding energies are made through the use of curvefitting routines applied to the peaks in the multiplex scan.
A NIST database is available to identify binding energies with specific compounds. Quantitation - The concentrations of the elements identified in the survey scan are determined by integrating the area under a characteristic peak for each element.
Sensitivity factors are applied to the peak area values to determine the elemental concentration. Cutting a sample is not always an option and can lead to added contamination of the area of interest. Samples must be compatible with high vacuum environment.
Samples must be amenable to a high vacuum environment ca. So, if your sample will outgas when placed under vacuum, XPS is not the right test for your needs. For manufacturers that make products where surface chemistry or thickness is critical to product function and safety, XPS testing and analysis could help you troubleshoot issues or ensure compliance with quality standards. Since Innovatech Labs has provided materials testing with extremely fast turnaround. While standard lead time is five business days or less, with expedited analysis, you can expect results in just hours.
Additionally, the change in bond energy chemical shift caused by the electron state surrounding the atoms to be analyzed, such as atomic valence charges and interatomic distances, tend to be greater than the chemical shift observed in AES, which makes the relative ease with which the state of chemical bonds can be identified another advantage of XPS. Secondary electron image observation SXI: Scanning X-ray Image based on this feature also allows for quick and accurate analysis location designation.
Additionally, it supports various analyses including multi-point simultaneous analysis, large area measurement, line analysis, and area analysis. However, with insulating material samples, a positive charge occurs in the x-ray irradiated area due to the generation of photoelectrons. A spectrum measured in a positively charged state shifts to the high bond energy side low kinetic energy side compared to its actual position, making it difficult to grasp the correct energy position.
Typically specific peaks of elements of interest are monitored to demonstrate relative changes in abundance or peak shifts in the binding energies that indicate changing bound states as a function of depth.
This sample has a thin film of B deposited on carbon steel. This depth profile was produced by selecting only the peaks of interest referred to as a multiplex routine , and then sequentially sputtering with the Ar gun for a fixed duration followed by analysis of the elements of interest.
Additional factors that may affect the quality of depth profiles include: a surface roughness of the sample, b redeposition of sputtered species, c "knock-on" effect that results in implantation or atomic mixing of surface components into the bulk, material; d differential sputtering rates of different chemical components; and e presence of crystal defects dislocations and underlying crystal structure.
Surveys of all elements present on a material surface can produce semi-quantitative analyses by measuring the area under each peak and applying appropriate elemental sensitivity factors from published tables, determined experimentally or theoretically; e. A general expression for quantitative analysis is:. For elements in numerous bound states on a material, high resolution scans that display deconvoluted spectra for a given element can be used to determine the relative abundances of each chemical state by integrating the area under the curve for each peak.
Typically, samples used for XPS analysis are analyzed "as received" because any chemical treatments will leave a contaminating residue. Here are some practical tips:. Data acquisition is conducted in two modes, Survey or Detailed high spectral resolution. The analytical mode is dictated by the type of information that is desired. Survey mode provides a complete inventory of elements present on a material surface.
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