EAL - Electron Effective Attenuation Length

Link to User's Guide for the NIST Electron Effective-Attenuation-Length Database

Link to Download NIST Electron-Attenuation-Length Database

Data needed for will include:
1) Inelastic mean free path data (density, number of valence electrons, band gap)

2) Asymmetry parameter (beta)

Inelastic Mean Free Path Calculations

Link to User's Guide to the NIST IMFP Calculator

Link to NIST IMFP Calculator at NIST website.

Data needed for inelastic mean free path (IMFP) calculations from predictive formula will include:
1) Density of the compound in g/cm-3 (the CRC Handbook is a good place to get this information)
2) Number of valence electrons in the compound - typically you will include electrons that have an excitation energy of less than 50 eV [1]
3) Band-Gap Energy (Eg) of the compound in eV - this is generally the hardest data to find and may not be available for all compounds

Reference:
[1] S. Tanuma, C.J. Powell, D.R. Penn, Surface and Interface Analysis, 17 (1991) 911-926.

Charge Correcting to C 1s In CasaXPS

1. Fit the C 1s peak (see this post for fitting the C 1s to adventitious carbon), obtain the binding energy for the main peak (C-C, C-H).
2. Select all peaks to be charge corrected.
3. Under Options, select Processing - Calibration tab.
4. Enter measured C 1s (C-C, C-H) peak binding energy.
5. Enter true C 1s binding energy (usually 284.8 eV for most work, 285.0 eV for polymer work).
6. Select (click boxes for) Regions and Components.
7. Press Apply to Selection (for multiple spectra) or Apply (for a single spectrum only).

X-ray Source Energies and Widths

XPS source energies and widths in eV.

Common sources for ultraviolet photoelectron spectroscopy (UPS) include He(I) at 21.22 eV and He(II) at 40.80 eV. Watts and Castle [4] present an excellent history on the development of  laboratory X-ray sources for XPS including higher energy sources used for HAXPES (hard X-ray photoelectron spectroscopy).  

References:

[1] G.M. Bancroft, H. W. Nesbitt, R. Ho, D. M. Shaw, J. S. Tse, M. C. Biesinger, Physical Review B 80 (2009) 075405.
[2] H.W. Nesbitt, G.M. Bancroft, R. Davidson, N.S. McIntyre, A.R. Pratt, American Mineralogist 85 (2004) 878-882.

[3] G.M. Bancroft, H.W. Nesbitt, V.P. Zakaznova-Herzog, J.S. Tse, Recent Advances in XPS of Non-Conductors in Turning Point in "Solid-State Materials and Surface Science" K.D.M. Harris and P.P. Edwards eds., Royal Society of Chemistry, pp. 651-664, 2007.

[4] J.F. Watts, J.E. Castle, Surface and Interface Analysis, 56 (2024) 408-424.

Indium 3d5/2 - M4N45N45 Auger Parameter

Indium MNN Auger spectrum.  The In M4N45N45 peak is shown with a peak fit to it. This is the more common peak to use for the calculation of the Auger parameter.

Note that the In M4N45N45 peak is the more common peak to use for the calculation of the Auger parameter.

In 3d5/2 - M4N45N45 Auger Parameter Values [1]

Reference:
[1] C.D. Wagner, A.V. Naumkin, A. Kraut-Vass, J.W. Allison, C.J. Powell, J.R.Jr. Rumble, NIST Standard Reference Database 20, Version 3.4 (web version) (http:/srdata.nist.gov/xps/) 2003.

Bromine

Br 3d5/2 binding energy values.

Note: Br 3d5/2 - 3d3/2 separation is 1.05 eV

Br 3p3/2: 182 eV
Br 3p1/2: 189 eV
Br 3s: 256 eV
Br 4s: 15 eV
Br 4d: 5 eV

Hydrogen and Helium

Hydrogen and helium are essentially impossible to detect by a lab-based XPS. Helium is not normally present as a solid and even when present (implanted) in a solid its 1s orbital has a very small cross-section for photoemission. Hydrogen also has an extremely small photoelectron cross-section and suffers from having to share its only electron in forming compounds, which then resides in a valence-like orbital.

Recent work [1] using a synchrotron based ambient pressure (AP) XPS has shown that it is possible to detect these elements with these specialized instruments.  A lower energy, high flux X-ray source increases the cross-section for H and He dramatically, and ambient pressure apparatus are needed to handle these gas phase elements.  Note that lab based AP-XPS cannot detect these elements - the synchrotron source is essential for this type of work.

Reference:
[1] J.-Q. Zhong, M. Wang, W.H. Hoffmann, M.A. van Spronsen, D. Lu, J.A. Boscoboinik, Appl. Phys. Lett. 112 (2018) 091602.

X-ray Degradation

It is important to remember that for certain samples the action of sample irradiation can change the sample chemistry - affecting the spectra obtained. This X-ray induced degradation is important to remember in the analysis of polymers and has been seen in the analysis of metal oxides. For polymers, keeping analysis time to a minimum can help negate this issue as can lowering the X-ray flux.

Metal oxides/hydroxides can also be susceptible to this effect. As local heating may play a role here one option to help mitigate this effect (in addition to minimizing analysis time or lowering the X-ray source flux) is to cool the samples using an in situ cooling stage (generally cooled using liquid nitrogen).  This has been shown to help in the analysis of copper and vanadium oxides [1].

Reference:
[1] M.C. Biesinger, L.W.M. Lau, A.R. Gerson, R.St.C. Smart, Resolving Surface Chemical States in XPS Analysis of First Row Transition Metals, Oxides and Hydroxides: Sc, Ti, V, Cu and Zn, Applied Surface Science, 257 (2010) 887-898.

Silver

The oxides of silver (along with cadmium) are of interest as they show an anomalous negative binding energy shift compared to the metal. For Ag2O and AgO the shifts are approximately -0.3 eV and -0.8 eV (see Table 1).  The predominant cause of this peculiar shift (according to [1]) is due to initial-state factors of ionic charge and lattice potential. It should be noted that both binding energies and Auger parameter values for Ag2O and AgO are quite similar, making species identification of the oxides in an unknown sample quite difficult.

Table 1. Ag 3d/52 binding energies and Ad 3d5/2 - Ag M4N45N45 Auger Parameters in eV [2].

Figure 1. Ag MVV Auger spectrum showing location of the M4VV or M4N45N45 peak used for Auger parameter analysis.

Notes [3]:  ISO 15472:2010 put metallic Ag 3d5/2 at 368.21 eV for calibration with a monochromatic Al K(alpha) X-ray source.
Ag 3d5/2 - 3d3/2 splitting: 6.00 eV
Ag 3p3/2: 573 eV
Ag 3p1/2: 604 eV
Ag 3s: 719 eV
Ag 4p: 60 eV
Ag 4s: 98 eV

References:
[1] S.W. Gaarenstroom, N. Winograd, J. Chem. Phys. 67 (1977) 3500.
[2] C.D. Wagner, A.V. Naumkin, A. Kraut-Vass, J.W. Allison, C.J. Powell, J.R.Jr. Rumble, NIST Standard Reference Database 20, Version 3.4 (web version) (http:/srdata.nist.gov/xps/) 2003.
[3] J.F. Moulder, W.F. Stickle, P.E. Sobol, K.D. Bomben "Handbook of X-Ray Photoelectron Spectroscopy", Perkin-Elmer Corporation, Physical Electronics Division, Eden Prairie, Minn. (1992)

Lead

Table 1. Lead 4f7/2 binding energy values (eV) [1].

Pb 4f7/2 - Pb 4f5/2 doublet separation = 4.88 eV +/- 0.05 eV (9 references).  [2] has it at 4.86 eV.

For the metal and sulfide (galena) the FWHM is fairly narrow at around 0.6-0.65 eV (20 eV pass energy). For PbCO3 the FWHM is about 1.46 eV (at 20 eV pass energy).

I've yet to be able to get good reference spectra for the oxides. Usually the peaks have been split although I'm not sure why just yet.  Possibly impure standards, X-ray degradation of the oxides, differential charging or a mix of all three. However, from the above data we see that the binding energy values for the various oxides overlap somewhat. The only good spectrum of an oxide I've taken is that for a sputtered cleaned surface that was then exposed to air for 1 minute.  A peak at 138.1 eV was recorded for this oxide with a FWHM of 1.26 eV (at 20 eV pass energy).

Also interesting is that the halide binding energy values don't change significantly down the series from the fluoride to the bromide and only slightly down with the iodide.

References:
[1] C.D. Wagner, A.V. Naumkin, A. Kraut-Vass, J.W. Allison, C.J. Powell, J.R.Jr. Rumble, NIST Standard Reference Database 20, Version 3.4 (web version) (http:/srdata.nist.gov/xps/) 2003.
[2] J.F. Moulder, W.F. Stickle, P.E. Sobol, K.D. Bomben, Handbook of X-ray Photoelectron Spectroscopy, Perkin-Elmer Corp, Eden Prairie, MN, 1992.