More information with higher photon energy
Depth profiling can be performed by analysing photoelectrons of different binding energies. In this case the Ag source is used to analyse the Si 2p and Si 1s core levels from a thin native oxide on Si. Clearly the higher BE (lower KE) Si 1s spectrum has a greater oxide ratio (Fig. 4 spectrum (b)) due to the reduced analysis depth when compared to the lower BE (higher KE) Si 2p spectrum, (Fig. 4 spectrum (a)).

Figure 4: Si 2p (a) and Si 1s (b) regions using Ag mono

Higher energy Auger series and core levels
The higher photon energy of the Ag source may be used to generate higher energy series. In this case Si KLL and Si 1s spectra were acquired from a native oxide on Si.

Figure 5:Si 1s and Si KLL Auger series excited with Ag mono source

Conclusions

The silver monochromatic source implemented within the geometry constraints of a classical aluminum monochromator has been shown to offer viable, narrow line, high energy excitation. The unique combination of the two sources in the same physical unit means that the silver source is also a practical option for routine high energy analysis. In addition, improved performance of modern magnetic lens instruments means that although the Bragg equation (for silver) is only satisfied by a second order diffraction, useable count rates and realistic acquisition times are achieved. It is expected that the introduction of the dual anode monochromatic source will lead to more studies of higher energy core levels and non-destructive depth profiling.

References

[1] Edgell et al., J. Electron Spec. & Rel. Phen. 37 (1985) pp 241-256

[2] K. Yates and R. H. West, Surf. Interf. Anal. Vol. 5, No. 4. (1983) pp 133-138

This paper was presented at AVS '99, the 46th International Symposium, Seattle, WA, 26th October 1999.