Silver Revisited

An article from Ana Ferraria et al. [1] at the Technical University of Lisbon presents some excellent results and analysis of a variety of silver species.  Ag 3d5/2 binding energies and Ag Auger parameters using both the M5N45N45 and M4N45N45 peak maxima are included (see Table 1). Curve-fitting of the Ag 3d5/2 line has also been carried out (Figure 1 and Table 1).  Of particular note is the presentation of high quality Ag MNN spectra which show distinct peak-shapes for metallic silver, AgNO3, Ag2O and AgO (Figure 2).

Table 1. XPS Ag 3d fitting parameters, Auger parameters and atomic ratios for Ag, AgNO3, Ag2O, AgO and a mechanically mixture of oxides (AgO + Ag2O)[1].

Figure 1. XPS detailed regions of Ag 3d for (top to bottom) Ag foil, AgNO3, Ag2O, AgO and a mechanical mixture of Ag2O and AgO [1].

Figure 2. XPS detailed regions of Ag MNN for (top to bottom) Ag foil, AgNO3, Ag2O, AgO and a mechanical mixture of Ag2O and AgO [1].

Reference:
[1] A.M. Ferraria, A.P. Carapeto, A.M. Botelho do Rego, Vacuum, 86 (2012) 1988-1991.

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]:
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)