Oxygen

Oxygen • Non-Metals

Primary XPS region: O1s
Overlapping regions: Na KLL, Sb3d, Pd3p, V2p
Binding energies of common chemical states:

Charge referenced to adventitious C1s peak at 284.8eV.

• The O1s region may be overlapped by peaks from antimony, palladium, or vanadium.
  • In the case of antimony, collect the full Sb3d / O1s region (525-550eV), making sure both Sb3d_5/2 and Sb3d_3/2 components are acquired.
  • In the case of palladium, collect the full Pd3p / O1s region (525–580eV), making sure both Pd3p_3/2 and Pd3p_1/2 components are acquired.
• During sputter depth profiling, it is preferable to collect data from the O1s region first in each data collection cycle.

• Interpretation of O1s spectra is not straightforward.
  • Apart from metal oxides, the O1s binding energy of many compounds and species falls within a very narrow range.
  • O1s peaks tend to be broad, with multiple overlapping components.
    • Components due to water and/or organic contamination overlap directly with SiO₂, for example.
    • Organic contamination also makes it difficult to discern carbonates in the O1s region.
    • It is typically not possible to uniquely peak fit these overlapping components.
    • The user normally has to impose peak fitting constraints, e.g. all overlapping components have the same (or similar) full width half-maximum.

• The peak fitting challenges mentioned above make it difficult to accurately quantify the oxygen chemical states.
  • In the copper (II) carbonate dihydroxide example shown above, the quantification of the carbonate versus hydroxide changes significantly according to peak fitting procedure.
• Metal oxides appear at a significantly different binding energy compared to most other oxygen species.
  • They also tend to have narrower O1s peaks compared to other species, e.g. carbonates.
  • It is often possible to directly observe the relative full width half-maximum of each component in the O1s spectrum.