Cobalt • Transition Metal

Primary XPS region: Co2p
Overlapping regions: Co LMM, Ba3d
Binding energies of common chemical states:

Chemical stateBinding energy Co2p3/2
Co metal778.2 eV
Co3O4779.7 eV
CoO779.7 eV

Experimental Information

  • Strong overlap between Ba3d and Co2p XPS peaks.
    • Check for Co LMM Auger peak ( 713 eV) or Ba4d peak ( 85 eV) for confirmation.
  • Cobalt oxides are readily reduced by Ar+ sputtering.
    • Use lowest possible ion beam energy when attempting to clean oxide sample surface or during depth profiling.
      • Minimizes (but does not completely prevent) reduction effect.

Interpretation of XPS spectra

  • Co2p peak has significantly split spin-orbit components (Δmetal=14.99eV)
  • Co2p region overlaps some of its own weaker Co LMM Auger peaks and care must be taken not to misinterpret the peak as an XPS peak.
  • Co2p peaks have asymmetric shape for metal.
    • A well resolved Co2p spectrum for metal shows complex structure.

XPS spectrum of cobalt metal

  • Possible to distinguish Co oxidation states using satellite features of Co2p spectrum.
    • Co (II) has observable satellite features ~786eV.
    • In the case of Co3O4, which is actually a mixed oxidation state of Co (II) and Co (III), we would expect to see some satellite features due to the 2+ and 3+ states.

XPS spectrum of cobalt oxides

General comments

  • Carbon may be implanted into cobalt metal forming carbides, e.g., during argon ion depth profiling.

crystal structureAbout This Element

Symbol: Co
Date of Discovery: 1737
Name Origin: German kobalt or kobold
Appearance: silver
Discoverer: George Brandt
Obtained From: arsenic, oxygen, sulfur, cobatine

Melting Point: 1768 K
Boiling Point: 3143 K
Density[kg/m3]: 8900
Molar Volume: 6.67 × 10-6 m3/mol
Protons/Electrons: 27
Neutrons: 32
Shell Structure: 2,8,15,2
Electron Configuration: [Ar]3d74s2
Oxidation State: 2,3
Crystal Structure: hexagonal

Frequently, cobalt is associated with nickel because both elements have characteristic ingredients of meteoric iron. This solid ferro- magnetic silver-white element was known in ancient times for its compounds, but its discovery was credited to G. Brandt between 1730 and 1737 when he was able to show that cobalt colors glass a rich blue. In small amounts, cobalt is an essential element for humans and many other living organisms, and it is also a central component of vitamin B-12 or cobalamin. Cobalt should be handled with care because of its toxicity and its risk factor in nuclear confrontation. Exposure to cobalt-60, a powerful gamma ray emitter, may cause cancer.

Application Notes

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