Indium •Other Metal

Primary XPS region: In3d
Overlapping regions: N/A
Binding energies of common chemical states:

Chemical stateBinding energy In3d5/2/eV
In metal443.8
In2O3444.0

Experimental Information

  • Small binding energy shifts of some compounds compared to indium metal.
    • Chemical state differentiation with can be difficult with XPS only.
    • Collect principal In MNN peak as well as In3d.
  • See trace In if used as powder mounting foil

Interpretation of XPS spectra

  • In3d region has well separated spin-orbit components (Δmetal=7.6eV).
    • Peaks have asymmetric peak shape for metal.
    • Loss features are observed to higher binding energy side of 3d3/2 spin-orbit component for In metal.
  • In3d peaks may also show asymmetry for indium oxide, if other compounds are present (e.g. hydroxide) or there are vacancies/defects in the oxide lattice.
  • Small or negligible binding energy shifts for compounds, such as oxides.
    • In3d peaks broaden with respect to metal peaks for compounds.
    • Subtle shifts in CIGS samples
    • Use X-ray induced In MNN Auger peaks to aid chemical state assignment.

crystal structureAbout This Element

Symbol: In
Date of Discovery: 1863
Name Origin: indigo spectrum
Appearance: silverish
Discoverer: Ferdinand Reich
Obtained From: zinc refining

Melting Point: 430 K
Boiling Point: 2345 K
Density[kg/m3]: 7310
Molar Volume: 15.76 × 10-6 m3/mol
Protons/Electrons: 49
Neutrons: 66
Shell Structure: 2,8,18,18,3
Electron Configuration: [Kr]4d105s25p1
Oxidation State: 3
Crystal Structure: tetragonal

Most elements were discovered while scientists searched for other materials, and indium is no exception. This very soft, silvery-white metal has a bright luster and emits a high-pitched “cry” when bent. One of the first major applications for indium was as a coating for bearings on high-performance aircraft during World War II. Later, tin-doped indium oxide, transparent and colorless in thin films, became a main component in liquid crystal, flat panel and plasma displays. Not surprisingly the demand for indium has risen dramatically, and lower cost alternatives such as carbon nanotubes and conducting polymers are being studied.

Application Notes

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