| AVS 66th International Symposium & Exhibition | |
| Applied Surface Science Division | Monday Sessions |
| Session AS+BI+RA-MoM |
| Session: | Quantitative Surface Analysis I/Reproducibility Issues in Quantitative XPS |
| Presenter: | Christopher Blomfield, Kratos Analytical Limited, UK |
| Authors: | A.G. Shard, National Physical Laboratory, UK J.D.P. Counsell, Kratos Analytical Limited, UK C.J. Blomfield, Kratos Analytical Limited, UK D.J.H. Cant, National Physical Laboratory, UK E.F. Smith, University of Nottingham, UK P. Navabpour, Teer Coatings Ltd, UK |
| Correspondent: | Click to Email |
The use of monochromated Ag La X-ray has been described previously.1, 2 These sources have now become more widely available on commercial instruments and easier to use due to automation and the superior collection efficiency of modern analysers. To enable direct comparison between data acquired using both sources it is essential to be able have a common calibration scheme and a set of useful sensitivity factors. We employ the calibration method developed by the National Physical Laboratory for Al Kα sources3 and extend this for Ag Lα sources.4 Sensitivity factors for Ag Lα and Al Kα are calculated from photoionisation cross sections and electron effective attenuation lengths. These compare well to previous experimental values and data acquired from ionic liquids. The intensity of the Ag Lα source is found to be approximately 50 times lower than the Al Kα source. This, coupled with generally lower photoemission efficiencies, results in noisier data or extended acquisition times. However, there are clear advantages to using the Ag Lα source to analyse certain elements where additional core levels can be accessed and for many technologically important elements where interference from Auger electron peaks can be eliminated. The combination of calibrated data from both sources provides direct and easily interpreted insight into the depth distribution of chemical species. This could be particularly important for topographic samples, where angle resolved experiments are not always helpful. We also demonstrate, using thin coatings of chromium and carbon, that the inelastic background in Ag Lα wide-scan spectra has a significantly increased information depth compared to Al Kα.
References
1. Yates, K.; West, R. Surf. Interface Anal. 1983,5 (4), 133-138.
2. Edgell, M.; Paynter, R.; Castle. J. Electron Spectr. Rel. Phenom. 1985,37 (2), 241-256
3. Seah, M. P.. J. Electron Spectr. Rel. Phenom. 1995,71 (3), 191-204.
4. Shard, A. G. et al. Surf. Interface Anal. 2019https://doi.org/10.1002/sia.6647