Arsenic

Arsenic is primarily analysed using the As(3d) region, which can overlap with the Ta(5p1/2) signal.  Generally observed as an oxide or in GaAs, the As(3d) region has a spin-orbit splitting of 0.7 eV, with an intensity ratio of 0.7, as opposed to the expected 0.67.

Recording the As(2p3/2) region is useful also and demonstrates oxide thickness as a function of kinetic energy (see below)

Figure 1: The As(3d) and As(2p3/2) regions of an as received GaAs sample. Green = elemental, blue = oxide

The As LMM Auger peaks when recorded with a Al source encompass a wide energy range (500 – 250 eV) and therefore overlap with many other photoemission lines, so care should be taken in analysis. This can be seen in the spectra below of As2O5.

Figure 2: Expansion of the survey spectrum for As2O5, showing the As LMM structure in the highlighted area

It has been reported that As2O3 sublimes in vacuum [1], whereas As5+ may under go some degredation by XPS analysis to yield As3+, so rapid analysis and/or summation of multi-point analysis may be required.

As3d5/2 Binding Energy / eV Charge Ref. (if known) Reference
As Metal 41.5 [2,3]
GaAs 40.9 [3]
As2O3 44.9 C(1s) at 284.8 eV [4]
As2O5 46.2 C(1s) at 284.8 eV [4]
NiAs 41.1 Au(4f) at 84.0 eV [5]
As(3d5/2) Binding energies

 

As2p3/2 Binding Energy / eV Reference
As Metal 1323.5 [2,3]
GaAs 1322.7 [3]
As2O3 1326.7 [4]
As2O5 1327.7 [4]
As(2p3/2) Binding energies

References

1. Arsenic entry at Thermo Scientific XPS Periodic Table

2. Arsenic entry at www.xpsfitting.com

3. Measured at HarwellXPS on Thermo Scientific K-Alpha+

4. Measured at HarwellXPS on Kratos Axis Ultra DLD system

5. H.W. Nesbitt and M. Reinke, American Mineralogist, 84 (1999) 629. Read online

Created: February 1, 2020