XPS is unique in being able to generate quantitative, chemical state information from a wide range of conducting, semiconducting and insulating materials. The information can be extremely surface sensitive, probing the outermost 1 -3 nm of the surface by angle resolved XPS. Higher energy X-ray excitation sources, such as Ag Lα (2984.2 eV) can be used to generate information from the near surface, up to 20 nm, whilst the destructive sputter depth profiling using Ar_n⁺ gas clusters can provide XPS data from several microns into the ‘bulk’ material.

These attributes of the modern spectrometer can be used in combination with in-situ modification of surface chemistry. Such an approach is of importance in gaining a better understanding of the functionality of materials. To aid research of these types of samples Kratos has developed a high pressure gas reaction cell allowing samples to be exposed to pressures up to 20 bar and temperatures of 1000 °C with static or dynamic gas flow conditions. The integrated gas handling system ensures that the samples can be processed for oxidation and reduction reactions dependent on the gases used. Use of this accessory is independent of the main analysis chamber with samples transferred from the gas reaction cell for analysis at normal UHV conditions. This approach ensures that the photoelectron transmission of the spectrometer remains constant and charge neutralisation is not compromised during the XPS analysis.

A further development for in-situ sample preparation is the integration of evaporation sources onto the AXIS spectrometers. The easy movement of samples through the spectrometer ensures that chemistry of thin-film deposition can be followed by XPS through the deposition cycles. It is also possible to compliment XPS measurements with low energy ion scattering spectroscopy (ISS), probing the outermost atomic layer of the sample and allowing the determination of film-closure for example.

This presentation will demonstrate the latest capabilities of the Kratos X-ray photoelectron spectrometers for lateral and depth distribution of elemental and chemical state through the characterisation of in-situ deposited and high temperature/pressure modified surfaces.

References:

1. L. K. Preethi, et al., Sci. Rep. 7, 14314 (2017)

2. M. Weis, et al., Sci. Rep. 7, 13782 (2017)

3. N. M. Freitag et al., Nature Nanotechn. 13, 392-397 (2018)

4. A. Momeni et al. J. Phys. Chem. Lett., 9, 908–913 (2018)

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