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X-ray photoelectron spectroscopy of thin films

Nature Reviews Methods Primers volume 3, Article number: 40 (2023) Cite this article

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Abstract

X-ray photoelectron spectroscopy (XPS) is a popular analytical technique in materials science as it can assess the surface chemistry of a broad range of samples. This Primer concerns best practice in XPS analysis, aimed at both entry-level and advanced users, with a focus on thin film samples synthesized under vacuum conditions. The high surface to volume ratio of thin films means that factors such as substrate choice and air exposure time are important for the final result. Essential concepts are introduced, such as binding energy, photoelectric effect, spectral referencing and chemical shift, as well as practical aspects including surface sensitivity, probing depth, energy resolution, sample handling and sputter etching. Correct procedures for experimental planning, instrument set-up, sample preparation, data acquisition, results analysis and presentation are reviewed in connection with physical principles and common applications. Typical problems, including charging, spectral overlap, sputter damage and binding energy referencing, are discussed along with possible solutions or workarounds. Finally, a workflow is presented for arriving at high-quality results.

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Fig. 1: A general overview of XPS.
Fig. 2: XPS peaks and peak fitting.
Fig. 3: Obtaining depth-resolved information from XPS.
Fig. 4: Thin capping layers enable spectra to be acquired free from sputter damage effects.
Fig. 5: Illustration of the benefit of analysing films in situ, without air exposure causing oxidation and contamination of the surface.
Fig. 6: Limitations and optimizations of XPS experiments.
Fig. 7: Zalar rotation for better depth resolution during sputter depth profiling.

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References

  1. Powell, C. J. Growth of surface analysis and the development of databases and modeling software for Auger-electron spectroscopy and X-ray photoelectron spectroscopy. Microsc. Today 24, 16 (2016).

    Article  Google Scholar 

  2. Powell, C. J. Improvements in the reliability of X-ray photoelectron spectroscopy for surface analysis. J. Chem. Educ. 81, 1734 (2004).

    Article  Google Scholar 

  3. Fadley, C. S. X-ray photoelectron spectroscopy: progress and perspectives. J. Electron Spectros. Relat. Phenomena 178–179, 2 (2010).

    Article  Google Scholar 

  4. Hofmann, S. Auger- and X-ray Photoelectron Spectroscopy in Materials Science (Springer-Verlag, 2013).

  5. Hűfner, S. Photoelectron Spectroscopy: Principles and Applications (Springer-Verlag, 2003).

  6. Briggs, D. & Grant, J. T. (eds) Surface Analysis by Auger and X-ray Photoelectron Spectroscopy (IM Publications, 2003).

  7. Baer, D. R. et al. Introduction to topical collection: reproducibility challenges and solutions with a focus on guides to XPS analysis. J. Vac. Sci. Technol. A 39, 021601 (2021).

    Article  Google Scholar 

  8. Greczynski, G. & Hultman, L. A step-by-step guide to perform X-ray photoelectron spectroscopy. J. Appl. Phys. 132, 011101 (2022). This work is a comprehensive guide to XPS.

    Article  ADS  Google Scholar 

  9. Major, G. H., Fernandez, V., Fairley, N., Smith, E. F. & Linford, M. R. Guide to XPS data analysis: applying appropriate constraints to synthetic peaks in XPS peak fitting. J. Vac. Sci. Technol. A 40, 063201 (2022).

    Article  Google Scholar 

  10. Bagus, P. S., Ilton, E. S. & Nelin, C. J. The interpretation of XPS spectra: insights into materials properties. Surf. Sci. Rep. 68, 273–304 (2013).

    Article  ADS  Google Scholar 

  11. Berni, M., Bontempi, M., Marchiori, G. & Gambardella, A. Roughness conformality during thin films deposition onto rough substrates: a quantitative study. Thin Solid Films 709, 138258 (2020).

    Article  ADS  Google Scholar 

  12. Hertz, H. Ueber sehr schnelle electrische Schwingungen [German]. Ann. Phys. 267, 421 (1887).

    Article  MATH  Google Scholar 

  13. Einstein, A. On a Heuristic point of view about the creation and conversion of light. Ann. Phys. 17, 132–148 (1905).

    Article  Google Scholar 

  14. Ashcroft, N. W. & Mermin, N. D. Solid State Physics (Saunders College Publishing, 1976).

  15. Ishii, H., Sugiyama, K., Ito, E. & Seki, K. Energy level alignment and interfacial electronic structures at organic/metal and organic/organic interfaces. Adv. Mater. 11, 605–625 (1999).

    Article  Google Scholar 

  16. Cahen, D. & Kahn, A. Electron energetics at surfaces and interfaces: concepts and experiments. Adv. Matter 15, 271 (2003).

    Article  ADS  Google Scholar 

  17. Meitner, L. Über die Entstehung der β-Strahl-Spektren radioaktiver Substanzen [German]. Z. Phys. 9, 131 (1922).

    Article  ADS  Google Scholar 

  18. Auger, P. Sur l’effet photoélectrique composé [French]. J. Phys. Radium 6, 205–208 (1925).

    Article  MATH  Google Scholar 

  19. Sokolowski, E., Nordling, C. & Siegbahn, K. Chemical shift effect in inner electronic levels of Cu due to oxidation. Phys. Rev. 110, 776 (1958).

    Article  ADS  Google Scholar 

  20. Hagström, S., Nordling, C. & Siegbahn, K. Electron spectroscopy for chemical analyses. Phys. Lett. 9, 235–236 (1964).

    Article  ADS  Google Scholar 

  21. Siegbahn, K. et al. ESCA — Atomic, Molecular and Solid State Structure Studied by Means of Electron Spectroscopy (Almquist & Wiksells, 1967).

  22. Hagström, S., Nordling, C. & Siegbahn, K. Electron spectroscopic determination of the chemical valence state. Z. Phys. 178, 439–444 (1964).

    Article  ADS  Google Scholar 

  23. Fahlman, A. et al. Electron spectroscopy and chemical binding. Nature 210, 4–8 (1966).

    Article  ADS  Google Scholar 

  24. Drummond, I. W. in Surface Analysis by Auger and X-ray Photoelectron Spectroscopy (eds Briggs, D. & Grant, J. T.) 117–144 (IM Publications, 2003).

  25. Egelhoff, W. F. Jr Core-level binding-energy shifts at surfaces and in solids. Surf. Sci. Rep. 6, 253–415 (1987). This work presents an exceptionally good overview of all basic concepts related to XPS such as binding energy, and initial and final state effects.

    Article  ADS  Google Scholar 

  26. Pauling, L. The nature of the chemical bond. IV. The energy of single bonds and the relative electronegativity of atoms. J. Am. Chem. Soc. 54, 3570–3582 (1932).

    Article  MATH  Google Scholar 

  27. International Organization for Standardization. ISO 18115-1, Surface Chemical Analysis — Vocabulary, Part 1 — General Terms and Terms Used in Spectroscopy (ISO, 2013).

  28. Tanuma, S., Powell, C. J. & Penn, D. R. Calculations of electron inelastic mean free paths for 31 materials. Surf. Interf. Anal. 11, 577 (1988).

    Article  Google Scholar 

  29. Tanuma, S., Powell, C. J. & Penn, D. R. Calculations of electron inelastic mean free paths II. Data for 27 elements over the 50–2000 eV range. Surf. Interf. Anal. 17, 911 (1991).

    Article  Google Scholar 

  30. Tanuma, S., Powell, C. J. & Penn, D. R. Calculations of electron inelastic mean free paths III. Data for 15 organic compounds over the 50–2000 eV range. Surf. Interf. Anal. 17, 927 (1991).

    Article  Google Scholar 

  31. Tanuma, S., Powell, C. J. & Penn, D. R. Calculations of electron inelastic mean free paths IV. Evaluation of calculated IMFPs and of the predictive IMFP formula TPP-2 for electron energies between 50 and 2000 eV. Surf. Interf. Anal. 21, 165 (1993).

    Article  Google Scholar 

  32. Powell, C. J. Practical guide for inelastic mean free paths, effective attenuation lengths, mean escape depths, and information depths in X-ray photoelectron spectroscopy. J. Vac. Sci. Technol. A 38, 023209 (2020). This important paper explains subtle differences between various terms frequently used in XPS jargon.

    Article  Google Scholar 

  33. Tanuma, S., Powell, C. J. & Penn, D. R. Calculations of electron inelastic mean free paths. IX. Data for 41 elemental solids over the 50 eV to 30 keV range. Surf. Interf. Anal. 43, 689–713 (2011). This work is an extremely useful resource for electron inelastic mean free paths.

    Article  Google Scholar 

  34. Shinotsuka, H., Tanuma, S., Powell, C. J. & Penn, D. R. Calculations of electron inelastic mean free paths. Data for 41 elemental solids over the 50 eV to 200 keV range with the relativistic full Penn algorithm. Surf. Interf. Anal. 47, 871 (2015).

    Article  Google Scholar 

  35. Shinotsuka, H., Tanuma, S., Powell, C. J. & Penn, D. R. Calculations of electron inelastic mean free paths. XII. Data for 42 inorganic compounds over the 50 eV to 200 keV range with the full Penn algorithm. Surf. Interf. Anal. 51, 427 (2019).

    Article  Google Scholar 

  36. Tanuma, S. et al. Experimental determination of electron inelastic mean free paths in 13 elemental solids in the 50 to 5000 eV energy range by elastic-peak electron spectroscopy. Surf. Interf. Anal. 37, 833 (2005).

    Article  Google Scholar 

  37. Werner, W. S. M., Tomastik, C., Cabela, T., Richter, G. & Störi, H. Elastic electron reflection for determination of the inelastic mean free path of medium energy electrons in 24 elemental solids for energies between 50 and 3400 eV. J. Electron. Spectros. Relat. Phenomena 113, 127 (2001).

    Article  Google Scholar 

  38. Seah, M. P. & Dench, W. A. Quantitative electron spectroscopy of surfaces: a standard data base for electron inelastic mean free paths in solids. Surf. Interf. Anal. 1, 2–11 (1979).

    Article  Google Scholar 

  39. Seah, M. P. Simple universal curve for the energy‐dependent electron attenuation length for all materials. Surf. Interf. Anal. 44, 1353–1359 (2012).

    Article  Google Scholar 

  40. Huchital, D. A. & McKeon, R. T. Use of an electron flood gun to reduce surface charging in X‐ray photoelectron spectroscopy. Appl. Phys. Lett. 20, 158 (1972).

    Article  ADS  Google Scholar 

  41. Baer, D. R. et al. XPS guide: charge neutralization and binding energy referencing for insulating samples. J. Vac. Sci. Technol. A 38, 031204 (2020).

    Article  Google Scholar 

  42. Edwards, L., Mack, P. & Morgan, D. J. Recent advances in dual mode charge compensation for XPS analysis. Surf. Interf. Anal. 51, 925–933 (2019).

    Article  Google Scholar 

  43. Greczynski, G., Petrov, I., Greene, J. E. & Hultman, L. Al capping layers for non-destructive X-ray photoelectron spectroscopy analyses of transition-metal nitride thin films. J. Vac. Sci. Technol. A 33, 05E101 (2015).

    Article  Google Scholar 

  44. Haasch, R. T., Patscheider, J., Hellgren, N., Petrov, I. & Greene, J. E. The Si3N4/TiN Interface: 1. TiN(001) grown and analyzed in situ using angle-resolved X-ray photoelectron spectroscopy. Surf. Sci. Spectra 19, 33 (2012).

    Article  ADS  Google Scholar 

  45. Lewin, E., Counsell, J. & Patscheider, J. Spectral artefacts post sputter-etching and how to cope with them — a case study of XPS on nitride-based coatings using monoatomic and cluster ion beams. Appl. Surf. Sci. 442, 487 (2018). This work is a good comparison of how etching with Ar+ ions and Ar ion clusters affects surface chemistry for nitride-based thin films.

    Article  ADS  Google Scholar 

  46. Seah, M. P. in Surface Analysis by Auger and X-ray Photoelectron Spectroscopy (eds Briggs, D. & Grant, J. T.) 167–189 (IM Publications, 2003).

  47. International Organization for Standardization. ISO 15472:2010, Surface chemical analysis — X-ray photoelectron spectrometers — Calibration of energy scales (ISO, 2010).

  48. Stevie, F. A., Garcia, R., Shallenberger, J., Newman, J. G. & Donley, C. L. Sample handling, preparation and mounting for XPS and other surface analytical techniques. J. Vac. Sci. Technol. A 38, 063202 (2020). This work is an excellent overview of all issues related to sample preparation and handling.

    Article  Google Scholar 

  49. Major, G. H. et al. Practical guide for curve fitting in X-ray photoelectron spectroscopy. J. Vac. Sci. Technol. A 38, 061203 (2020). This work is a very comprehensive source of information for peak fitting XPS spectra.

    Article  Google Scholar 

  50. Gadzuk, J. W. & Doniach, S. A soluble relaxation model for core level spectroscopy on adsorbed atoms. Surf. Sci. 77, 154855 (1978).

    Article  Google Scholar 

  51. Veal, B. W. & Paulikas, A. P. Final-state screening and chemical shifts in photoelectron spectroscopy. Phys. Rev. B 31, 5399 (1985).

    Article  ADS  Google Scholar 

  52. Haasch, R. T., Patscheider, J., Hellgren, N., Petrov, I. & Greene, J. E. The Si3N4/TiN interface: an introduction to a series of ultrathin films grown and analyzed in situ using X-ray photoelectron spectroscopy. Surf. Sci. Spectra 19, 30–32 (2012).

    Article  ADS  Google Scholar 

  53. Naumkin, A. V., Kraut-Vass, A., Gaarenstroom, S. W. & Powell, C. J. NIST X-ray photoelectron spectroscopy database, version 4.1. National Institute of Standards and Technology http://srdata.nist.gov/xps/ (2012).

  54. Crist, B. V. XPS in industry — problems with binding energies in journals and binding energy databases. J. Electron Spectros. Relat. Phenomena 231, 75–87 (2019).

    Article  Google Scholar 

  55. Baer, D. R. & Shard, A. G. Role of consistent terminology in XPS reproducibility. J. Vac. Sci. Technol. A 38, 031203 (2020).

    Article  Google Scholar 

  56. Haasch, R. T. & Abraham, D. P. LiNi0.8Co0.2O2-based high power lithium-ion battery positive electrodes analyzed by X-ray photoelectron spectroscopy: 1. Fresh electrode. Surf. Sci. Spectra 23, 118 (2016).

    Article  ADS  Google Scholar 

  57. Greczynski, G. & Hultman, L. Self-consistent modeling of X-ray photoelectron spectra from air-exposed polycrystalline TiN thin films. Appl. Surf. Sci. 387, 294 (2016).

    Article  ADS  Google Scholar 

  58. Engelhard, M. H., Baer, D. R., Herrera-Gomez, A. & Sherwood, P. M. A. Introductory guide to backgrounds in XPS spectra and their impact on determining peak intensities. J. Vac. Sci. Technol. A 38, 063203 (2020).

    Article  Google Scholar 

  59. Repoux, M. Comparison of background removal methods for XPS. Surf. Interf. Anal. 18, 567–570 (1992).

    Article  Google Scholar 

  60. Brundle, C. R. & Crist, B. V. X-ray photoelectron spectroscopy: a perspective on quantitation accuracy for composition analysis of homogeneous materials. J. Vac. Sci. Technol. A 38, 041001 (2020).

    Article  Google Scholar 

  61. Baker, M. 1500 scientists lift the lid on reproducibility. Nature 533, 452 (2016).

    Article  ADS  Google Scholar 

  62. Briggs, D. & Seah, M. P. Practical Surface Analysis: Auger and X-ray Photoelectron Spectroscopy Vol. 1 233–239 555–586 (Wiley, 1990).

  63. Shirley, D. A. High-resolution X-ray photoemission spectrum of the valence bands of gold. Phys. Rev. B 5, 4709 (1972).

    Article  ADS  Google Scholar 

  64. Proctor, A. & Sherwood, P. M. A. Data analysis techniques in X-ray photoelectron spectroscopy. Anal. Chem. 54, 13 (1982).

    Article  Google Scholar 

  65. Tougaard, S. Universality classes of inelastic electron scattering cross-sections. Surf. Interf. Anal. 25, 137 (1997).

    Article  Google Scholar 

  66. Fairley, N. & Carrick, A. The Casa Cookbook Part 1: Recipes for XPS Data Processing 147–167 (Acolyte Science, 2005).

  67. Citrin, P. H. & Hamann, D. R. Phonon broadening of X-ray photoemission line shapes in solids and its independence of hole state lifetimes. Phys. Rev. B 15, 2923 (1977).

    Article  ADS  Google Scholar 

  68. Powell, C. J. & Jablonski, A. Progress in quantitative surface analysis by X-ray photoelectron spectroscopy: current status and perspectives. J. Electron. Spectros. Relat. Phenomena 178–179, 331–346 (2010).

    Article  Google Scholar 

  69. Brundle, C. R., Crist, B. V. & Bagus, P. S. Accuracy limitations for composition analysis by XPS using relative peak intensities: LiF as an example. J. Vac. Sci. Technol. A https://doi.org/10.1116/6.0000674 (2021).

    Article  Google Scholar 

  70. Shard, A. G. Practical guides for x-ray photoelectron spectroscopy: quantitative XPS. J. Vac. Sci. Technol. A 38, 041201 (2020).

    Article  Google Scholar 

  71. Jablonski, A. & Powell, C. J. Effective attenuation lengths for quantitative determination of surface composition by Auger-electron spectroscopy and X-ray photoelectron spectroscopy. J. Electron Spectros. Relat. Phenomena 281, 1–12 (2017).

    Article  Google Scholar 

  72. Tougaard, S. Surface nanostructure determination by X-ray photoemission spectroscopy peak shape analysis. J. Vac. Sci. Technol. A 14, 1415–1423 (1996).

    Article  Google Scholar 

  73. Tougaard, S. Practical guide to the use of backgrounds in quantitative XPS. J. Vac. Sci. Technol. A https://doi.org/10.1116/6.0000661 (2021).

    Article  Google Scholar 

  74. Zborowski, C., Vanleenhove, A. & Conard, T. Comparison and complementarity of QUASES-Tougaard and SESSA software. Appl. Surf. Sci. https://doi.org/10.1016/j.apsusc.2022.152758 (2022).

    Article  Google Scholar 

  75. Smekal, W., Werner, W. S. M. & Powell, C. J. Simulation of electron spectra for surface analysis (SESSA): a novel software tool for quantitative Auger-electron spectroscopy and X-ray photoelectron spectroscopy. Surf. Interf. Anal. 37, 1059–1067 (2005).

    Article  Google Scholar 

  76. Werner, W. S. M. & Powell, C. J. Applications of the National Institute of Standards and Technology (NIST) database for the simulation of electron spectra for surface analysis for quantitative x-ray photoelectron spectroscopy of nanostructures. J. Vac. Sci. Technol. A 39, 063205 (2021).

    Article  Google Scholar 

  77. Hellgren, N. et al. X-ray photoelectron spectroscopy analysis of TiBx (1.3 ≤ x ≤ 3.0) thin films. J. Vac. Sci. Technol. A https://doi.org/10.1116/6.0000789 (2021).

    Article  Google Scholar 

  78. Strohmeier, B. R. An ESCA method for determining the oxide thickness on aluminum alloys. Surf. Interf. Anal. 15, 51–56 (1990).

    Article  Google Scholar 

  79. Carlson, T. A. Basic assumptions and recent developments in quantitative XPS. Surf. Interf. Anal. 4, 125–134 (1982).

    Article  Google Scholar 

  80. Hofmann, S. Auger- and X-ray Photoelectron Spectroscopy in Materials Science Ch. 4.3.3 (Springer-Verlag, 2013).

  81. Unarunotai, S. et al. Layer-by-layer transfer of multiple, large area sheets of graphene grown in multilayer stacks on a single SiC wafer. ACS Nano 4, 5591 (2010).

    Article  Google Scholar 

  82. Madsen, K. E. et al. Origin of enhanced cyclability in covalently modified LiMn1.5Ni0.5O4 cathodes. ACS Appl. Mater. Interfaces. 11, 39890 (2019).

    Article  Google Scholar 

  83. Hanifpour, F. et al. Operando quantification of ammonia produced from computationally-derived transition metal nitride electro-catalysts. J. Catal. 413, 956 (2022).

    Article  Google Scholar 

  84. Hellgren, N., Haasch, R. T., Schmidt, S., Hultman, L. & Petrov, I. Interpretation of X-ray photoelectron spectra of carbon-nitride thin films: new insights from in situ XPS. Carbon 108, 242–252 (2016).

    Article  Google Scholar 

  85. Hellgren, N. et al. Electronic structure of carbon nitride thin films studied by X-ray spectroscopy techniques. Thin Solid Films 471, 19–34 (2005).

    Article  ADS  Google Scholar 

  86. Hellgren, N., Johansson, M. P., Broitman, E., Hultman, L. & Sundgren, J.-E. Role of nitrogen in the formation of hard and elastic CNx thin films by reactive magnetron sputtering. Phys. Rev. B 57, 5164–5169 (1999).

    Google Scholar 

  87. Patscheider, J., Hellgren, N., Haasch, R. T., Petrov, I. & Greene, J. E. Electronic structure of the SiNx/TiN interface: a model system for superhard nanocomposites. Phys. Rev. B https://doi.org/10.1103/PhysRevB.83.125124 (2011).

    Article  Google Scholar 

  88. Greczynski, G., Mraz, S., Hultman, L. & Schneider, J. M. Substantial difference in target surface chemistry between reactive DC and high power impulse magnetron sputtering. J. Phys. D Appl. Phys. 51, 05LT01 (2018).

    Article  Google Scholar 

  89. Greczynski, G., Primetzhofer, D., Lu, J. & Hultman, L. Core-level spectra and binding energies of transition metal nitrides by non-destructive X-ray photoelectron spectroscopy through capping layers. Appl. Surf. Sci. 396, 347 (2017).

    Article  ADS  Google Scholar 

  90. Greczynski, G., Mráz, S., Hultman, L. & Schneider, J. M. Native target chemistry during reactive DC magnetron sputtering studied by ex situ X-ray photoelectron spectroscopy. Appl. Phys. Lett. 111, 021604 (2017).

    Article  ADS  Google Scholar 

  91. Prieto, P. & Kirby, R. E. X‐ray photoelectron spectroscopy study of the difference between reactively evaporated and direct sputter‐deposited TiN films and their oxidation properties. J. Vac. Sci. Technol. A 13, 2819 (1995).

    Article  Google Scholar 

  92. Biwer, B. M. & Bernasek, S. L. Electron spectroscopic study of the iron surface and its interaction with oxygen and nitrogen. J. Electron. Spectros. Relat. Phenomena 40, 339 (1986).

    Article  Google Scholar 

  93. Haasch, R. T. et al. X-ray and ultraviolet photoelectron spectroscopic analyses of single-crystal TiN(001). I. Analysis of as-deposited layers. Surf. Sci. Spectra 7, 193–203 (2000).

    Article  ADS  Google Scholar 

  94. NIST. NIST Chemistry WebBook. National Institute of Standards and Technology http://webbook.nist.gov/chemistry/ (2023).

  95. Major, G. H. et al. Assessment of the frequency and nature of erroneous X-ray photoelectron spectroscopy analyses in the scientific literature. J. Vac. Sci. Technol. A 38, 061203 (2020).

    Article  Google Scholar 

  96. Herrera-Gomez, A. Uncertainties in photoemission peak fitting accounting for the covariance with background parameters. J. Vac. Sci. Technol. A 38, 033211 (2020).

    Article  Google Scholar 

  97. Jain, V., Biesinger, M. C. & Linford, M. R. The Gaussian–Lorentzian sum, product, and convolution (Voigt) functions in the context of peak fitting X-ray photoelectron spectroscopy (XPS) narrow scans. Appl. Surf. Sci. 447, 548–553 (2018). This work is an excellent source of information about various peak functions used in peak fitting XPS spectra.

    Article  ADS  Google Scholar 

  98. Greczynski, G. & Hultman, L. X-ray photoelectron spectroscopy: towards reliable binding energy referencing. Prog. Mat. Sci. 107, 100591 (2020). This review article presents a special emphasis on the charge referencing issue in XPS.

    Article  Google Scholar 

  99. Greczynski, G. & Hultman, L. Impact of sample storage type on adventitious carbon and native oxide growth: X-ray photoelectron spectroscopy study. Vacuum 205, 111463 (2022).

    Article  ADS  Google Scholar 

  100. Baer, D., Gaspar, D. J., Engelhard, M. H. & Lea, A. S. in Surface Analysis by Auger and X-ray Photoelectron Spectroscopy (eds Briggs, D. & Grant, J. T.) 211–234 (IM Publications, 2003).

  101. Conard, T., Vanleenhove, A. & van der Heide, P. Achieving reproducible data: examples from surface analysis in semiconductor technology. J. Vac. Sci. Technol. A 38, 033206 (2020).

    Article  Google Scholar 

  102. Greczynski, G., Mráz, S., Hultman, L. & Schneider, J. M. Unintentional carbide formation evidenced during high-vacuum magnetron sputtering of transition metal nitride thin films. Appl. Surf. Sci. 385, 356 (2016).

    Article  ADS  Google Scholar 

  103. Greczynski, G., Mráz, S., Hultman, L. & Schneider, J. M. Venting temperature determines surface chemistry of magnetron sputtered TiN films. Appl. Phys. Lett. 108, 041603 (2016).

    Article  ADS  Google Scholar 

  104. Betz, G. Alloy sputtering. Surf. Sci. 92, 283 (1980).

    Article  ADS  Google Scholar 

  105. Tarng, M. L. & Wehner, G. K. Alloy sputtering studies with in situ Auger electron spectroscopy. J. Appl. Phys. 42, 2449 (1971).

    Article  ADS  Google Scholar 

  106. Wang, Y. X. & Holloway, P. H. Effect of ion sputtering on the interface chemistry and electrical properties of Au/n‐GaAs(100) Schottky contacts. J. Vac. Sci. Technol. A 2, 567 (1984).

    Article  Google Scholar 

  107. Hammer, G. E. & Shemenski, R. M. Preferential sputtering of brass studied by AES and XPS. J. Vac. Sci. Technol. A 2, 1132 (1984).

    Article  Google Scholar 

  108. Oswald, S. & Brückner, W. XPS depth profile analysis of non-stoichiometric NiO films. Surf. Interf. Anal. 36, 17–22 (2004).

    Article  Google Scholar 

  109. Steinberger, R. et al. XPS study of the effects of long-term Ar+ ion and Ar cluster sputtering on the chemical degradation of hydrozincite and iron oxide. Corros. Sci. 99, 66–75 (2015).

    Article  Google Scholar 

  110. Xie, F. Y. et al. XPS studies on surface reduction of tungsten oxide nanowire film by Ar+ bombardment. J. Electron Spectros. Relat. Phenomena 185, 112–118 (2012).

    Article  Google Scholar 

  111. Simpson, R., White, R. G., Watts, J. F. & Baker, M. A. XPS investigation of monatomic and cluster argon ion sputtering of tantalum pentoxide. Appl. Surf. Sci. 405, 79–87 (2017).

    Article  ADS  Google Scholar 

  112. Ahlberg, P. et al. Defect formation in graphene during low-energy ion bombardment. APL Mater. 4, 046104 (2016).

    Article  ADS  Google Scholar 

  113. Sundberg, J. et al. Understanding the effects of sputter damage in W–S thin films by HAXPES. Appl. Surf. Sci. 305, 203–213 (2014).

    Article  ADS  Google Scholar 

  114. Lewin, E., Gorgoi, M., Schäfers, F., Svensson, S. & Jansson, U. Influence of sputter damage on the XPS analysis of metastable nanocomposite coatings. Surf. Coat. Technol. 204, 455–462 (2009).

    Article  Google Scholar 

  115. Greczynski, G. & Hultman, L. Towards reliable X-ray photoelectron spectroscopy: sputter-damage effects in transition metal borides, carbides, nitrides, and oxides. Appl. Surf. Sci. 542, 148599 (2021).

    Article  Google Scholar 

  116. Koenig, M. F. & Grant, J. T. Signal‐to‐noise measurement in X‐ray photoelectron spectroscopy. Surf. Interf. Anal. 7, 217 (1985).

    Article  Google Scholar 

  117. Mähl, S., Neumann, M., Dieckhoff, S., Schlett, V. & Baalmann, A. Characterisation of the VG ESCALAB instrumental broadening functions by XPS measurements at the Fermi edge of silver. J. Electron Spectros. Relat. Phenomena 85, 197 (1997).

    Article  Google Scholar 

  118. Cazaux, J. Mechanisms of charging in electron spectroscopy. J. Electron Spectros. Relat. Phenomena 105, 155 (1999).

    Article  Google Scholar 

  119. Baer, D. R., Engelhard, M. H., Gaspar, D. J., Lea, A. S. & Windisch, C. F. Jr. Use and limitations of electron flood gun control of surface potential during XPS: two non‐homogeneous sample types. Surf. Interf. Anal. 33, 781–790 (2002). This work is a very good illustration of practical aspects of sample charging and the use of flood guns.

    Article  Google Scholar 

  120. Tielsch, B. J., Fulghum, J. E. & Surman, D. J. Differential charging in XPS. Part II: sample mounting and X‐ray flux effects on heterogeneous samples. Surf. Interf. Anal. 24, 459–468 (1996).

    Article  Google Scholar 

  121. Tielsch, B. J. & Fulghum, J. E. Differential charging in XPS. Part I: demonstration of lateral charging in a bulk insulator using imaging XPS. Surf. Interf. Anal. 24, 422–427 (1996).

    Article  Google Scholar 

  122. Tielsch, B. J. & Fulghum, J. E. Differential charging in XPS. Part III. A comparison of charging in thin polymer overlayers on conducting and non‐conducting substrates. Surf. Interf. Anal. 25, 904–912 (1997).

    Article  Google Scholar 

  123. Schön, G. High resolution Auger electron spectroscopy of metallic copper. J. Electron. Spectrosc. 1, 377 (1973).

    Article  Google Scholar 

  124. Richter, K. & Peplinski, B. Energy calibration of electron spectrometers. J. Electron. Spectrosc. 13, 69 (1978).

    Article  Google Scholar 

  125. Bird, R. J. & Swift, P. Energy calibration in electron spectroscopy and the re-determination of some reference electron binding energies. J. Electron. Spectrosc. 21, 227 (1980).

    Article  Google Scholar 

  126. Anthony, M. T. & Seah, M. P. XPS: energy calibration of electron spectrometers. 1 — An absolute, traceable energy calibration and the provision of atomic reference line energies. Surf. Interf. Anal. 6, 95 (1984).

    Article  Google Scholar 

  127. Crist, B. V. Handbooks of Monochromatic XPS Spectra — The Elements and Native Oxides Vol. 1 (XPS, 1999).

  128. Swift, P. Adventitious carbon — the panacea for energy referencing? Surf. Interf. Anal. 4, 47–51 (1982).

    Article  Google Scholar 

  129. Hnatowich, D. J., Hudis, J., Perlman, M. L. & Ragaini, R. C. Determination of charging effect in photoelectron spectroscopy of nonconducting solids. J. Appl. Phys. 42, 4883–4886 (1971).

    Article  ADS  Google Scholar 

  130. Johansson, G., Hedman, J., Berndtsson, A., Klasson, M. & Nilsson, R. Calibration of electron spectra. J. Electron. Spectrosc. 2, 295 (1973).

    Article  Google Scholar 

  131. Dianis, W. P. & Lester, J. E. External standards in X-ray photoelectron spectroscopy. Comparison of gold, carbon, and molybdenum trioxide. Anal. Chem. 45, 1416–1420 (1973).

    Article  Google Scholar 

  132. Nordberg, R., Brecht, H., Albridge, R. G., Fahlman, A. & Van Wazer, J. R. Binding energy of the “2p” electrons of silicon in various compounds. Inorg. Chem. 9, 2469–2474 (1970).

    Article  Google Scholar 

  133. Kinoshita, S., Ohta, T. & Kuroda, H. Comments on the energy calibration in X-ray photoelectron spectroscopy. Bull. Chem. Soc. Jpn. 49, 1149–1150 (1976).

    Article  Google Scholar 

  134. Greczynski, G. & Hultman, L. C 1s peak of adventitious carbon aligns to the vacuum level: dire consequences for material’s bonding assignment by photoelectron spectroscopy. ChemPhysChem 18, 1507 (2017).

    Article  Google Scholar 

  135. Greczynski, G. & Hultman, L. Compromising science by ignorant instrument calibration — need to revisit half a century of published XPS data. Angew. Chem. Int. Ed. 59, 5002 (2020).

    Article  Google Scholar 

  136. Greczynski, G. & Hultman, L. Reliable determination of chemical state in X-ray photoelectron spectroscopy based on sample–work–function referencing to adventitious carbon: resolving the myth of apparent constant binding energy of the C 1s peak. Appl. Surf. Sci. 451, 99 (2018).

    Article  ADS  Google Scholar 

  137. Greczynski, G. & Hultman, L. The same chemical state of carbon gives rise to two peaks in X-ray photoelectron spectroscopy. Sci. Rep. 11, 11195 (2021).

    Article  ADS  Google Scholar 

  138. Greczynski, G. & Hultman, L. Referencing to adventitious carbon in X-ray photoelectron spectroscopy: can differential charging explain C 1s peak shifts? Appl. Surf. Sci. 606, 154855 (2022).

    Article  Google Scholar 

  139. Zalar, A. Improved depth resolution by sample rotating during Auger electron spectroscopy depth profiling. Thin Solid Films 124, 223 (1985).

    Article  ADS  Google Scholar 

  140. Zalar, A. & Hofmann, S. Comparison of rotational depth profiling with AES and XPS. Appl. Surf. Sci. 68, 361–367 (1993).

    Article  ADS  Google Scholar 

  141. Kalha, C. et al. Hard X-ray photoelectron spectroscopy: a snapshot of the state-of-the-art in 2020. J. Phys. Condens. Matter 33, 233001 (2021).

    Article  ADS  Google Scholar 

  142. Greczynski, G., Kindlund, H., Petrov, I., Greene, J. & Hultman, L. Sputter-cleaned epitaxial VxMo1–xNy/MgO(001) thin films analyzed by X-ray photoelectron spectroscopy: 1. Single-crystal V0.48Mo0.52N0.64. Surf. Sci. Spectra 20, 68 (2013).

    Article  ADS  Google Scholar 

  143. Evans, S. Work function measurements by X-Pe spectroscopy, and their relevance to the calibration of X-Pe spectra. Chem. Phys. Lett. 23, 134–138 (1973).

    Article  ADS  Google Scholar 

  144. Wagner, C. D. Chemical shifts of Auger lines, and the Auger parameter. Faraday Discuss. Chem. Soc. 60, 291–300 (1975).

    Article  Google Scholar 

  145. Wagner, C. D. Auger parameter in electron spectroscopy for the identification of chemical species. Anal. Chem. 47, 1201–1203 (1975).

    Article  Google Scholar 

  146. Stevie, F. A. & Donley, C. L. Introduction to X-ray photoelectron spectroscopy. J. Vac. Sci. Technol. A 38, 063204 (2020).

    Article  Google Scholar 

  147. Yamada, I., Matsuo, J., Toyoda, N., Aoki, T. & Seki, T. Progress and applications of cluster ion beam technology. Curr. Opin. Solid State Mater. Sci. 19, 12–18 (2015).

    Article  ADS  Google Scholar 

  148. Fisher, G. L., Dickinson, M., Bryan, S. R. & Moulder, J. C60 sputtering of organics: a study using TOF-SIMS, XPS and nanoindentation. Appl. Surf. Sci. 255, 819–823 (2008).

    Article  ADS  Google Scholar 

  149. Miyayama, T. et al. X-ray photoelectron spectroscopy study of polyimide thin films with Ar cluster ion depth profiling. J. Vac. Sci. Technol. A 28, L1–L4 (2010).

    Article  Google Scholar 

  150. Barlow, A. J., Portoles, J. F. & Cumpson, P. J. Observed damage during argon gas cluster depth profiles of compound semiconductors. J. Appl. Phys. 116, 054908 (2014).

    Article  ADS  Google Scholar 

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Acknowledgements

The authors acknowledge the financial support of the Swedish Research Council (VR Grant 2018-03957), the Swedish Energy Agency (under project 51201-1), the Knut and Alice Wallenberg Foundation (Scholar Grant KAW2019.0290), the Carl Tryggers Stiftelse (contract CTS 20:150), the Competence Center Functional Nanoscale Materials (FunMat-II) VINNOVA (grant 2022-03071) and the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University (Faculty Grant SFO-Mat-LiU No. 2009-00971). The Icelandic Research Fund (grant number 196437-051) is acknowledged for funding the research leading to the application example shown in Fig. 3. Portions of this work were carried out at the Materials Research Laboratory Central Research Facilities, University of Illinois, USA.

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Authors and Affiliations

  1. Thin Film Physics Division, Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping, Sweden

    Grzegorz Greczynski & Lars Hultman

  2. Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL, USA

    Richard T. Haasch

  3. Department of Computing, Mathematics, and Physics, Messiah University, Mechanicsburg, PA, USA

    Niklas Hellgren

  4. Department of Chemistry — Ångström Laboratory, Uppsala University, Uppsala, Sweden

    Erik Lewin

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  1. Grzegorz Greczynski
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Contributions

Introduction (G.G., L.H. and N.H.); Experimentation (E.L. and G.G.); Results (R.T.H., N.H. and G.G.); Applications (R.T.H., E.L., N.H. and G.G.); Reproducibility and data deposition (R.T.H. and G.G.); Limitations and optimizations (G.G., L.H. and E.L.); Outlook (G.G. and E.L.); Overview of the Primer (G.G. and L.H.).

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Correspondence to Grzegorz Greczynski.

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Nature Reviews Methods Primers thanks Thierry Conard, who co-reviewed with Anja Vanleenhove; Beth Willneff; and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Related links

American Society for Testing and Materials International: https://www.astm.org/

AVS Science and Technology of Materials, Interfaces, and Processing Society: https://avs.org/

CasaXPS: http://www.casaxps.com/

International Organization for Standardization: https://www.iso.org/

LaSurface: http://www.lasurface.com/database/index.php

QUASES: http://www.quases.com/

XPS reference page: http://www.xpsfitting.com/

Supplementary information

Glossary

Auger electron

An electron emitted from an atom following the filling of the core hole vacancy.

Binding energy

(EB). The difference between the total energy of the system (an atom or a molecule) before and after emission of a core-level electron.

Calibration of energy scale

The procedure performed on a regular basis to check whether the signals from reference samples, such as sputter-etched gold, silver or copper foils, appear at the correct energy value.

Charge referencing

A necessary step in data analysis to eliminate possible influence of sample charging on the results.

Chemical shifts

Measurable changes in the binding energy of X-ray photoelectron spectroscopy (XPS) peaks resulting from changes in the valence charge density (chemical environment) on concerned atoms.

Core electron

An electron originating from an inner atomic shell.

Core hole

A core hole is created when a core electron is removed from an atom due to, for example, photoemission.

Electron emission angle

(θ). The angle between the sample surface normal and the direction connecting the analyser entry slit with the sample.

Energy resolution

The ability of a given instrument to differentiate between electrons leaving the surface with different kinetic energy.

Fermi edge

A rapid drop in the density of states that occurs at the Fermi level for metallic samples and serves as an internal energy reference level.

Fermi level

(EF). The energy level where the probability of finding an electron is 0.5 and in the case of metals corresponds to the highest occupied state.

Flood gun

A device that enables spectra to be acquired from insulating samples by supplying a flux of low-energy electrons at the surface that compensates for the charge loss resulting from photoemission.

High-resolution spectra

Narrow-range spectra (10–20 eV) recorded with a fine energy step (0.1 eV or less) and low pass energy for the best energy resolution.

Inelastic mean free path

(λ). The average distance travelled by an electron between two collisions where its kinetic energy changes.

Natural line width

Determined by the uncertainty principle and differs between anode types. Modern instruments typically use monochromators to limit the energy spread of exciting radiation and improve energy resolution.

Pass energy

(EP). The kinetic energy of electrons travelling through the hemispherical analyser, an important parameter that defines energy resolution.

Photoelectric effect

The phenomenon where electrons are emitted from surfaces exposed to light of sufficiently high energy.

Probing depth

The thickness of the surface layer that accounts for 95% of the collected signal.

Relative sensitivity factor

(RSF). An empirically derived number used in quantitative analysis to scale peak areas so that they are proportional to elemental concentrations.

Spin–orbit doublet

A pair of X-ray photoelectron spectroscopy (XPS) peaks with a characteristic energy separation and intensity ratio that appears due to the spin–orbit interaction.

Sputter etch

A surface treatment where bombardment with noble gas ions is used to remove either surface oxides and contamination or layers of sample material in depth profiling.

Surface charging

The accumulation of positive charge in the top surface layer if the charge lost due to photoemission is not compensated by electrons from the substrate or surroundings.

Survey spectra

Wide energy range overview spectra, for example from 1,300 to 0 eV for an Al Kα excitation source, typically recorded with high pass energy to detect signals from all elements present at the surface.

Take-off angle

The angle between the sample surface plane and the direction connecting the analyser entry slit with the sample, equal to 90o – θ.

Vacuum level

(EVL). An energy reference level corresponding to an electron at rest and outside any solid.

Work function

(\(\phi \)SA). The minimum amount of energy necessary to remove an electron from a solid immediately outside its surface.

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Greczynski, G., Haasch, R.T., Hellgren, N. et al. X-ray photoelectron spectroscopy of thin films. Nat Rev Methods Primers 3, 40 (2023). https://doi.org/10.1038/s43586-023-00225-y

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