Zinc

Zinc • Transition Metal

Primary XPS region: Zn2p
Overlapping regions: O KLL, V LMM
Binding energies of common chemical states:

Chemical state	Binding energy Zn2p_3/2
Zn metal	1,021.7 eV
ZnO	~1,022 eV

Oxide charge referenced to adventitious C1s peak at 284.8eV.

Experimental Information

There are small binding energy shifts of some compounds compared to zinc metal.
- Chemical state differentiation can be difficult with XPS only.
- Collect principal Zn LMM peak as well as Zn2p.
  - There are bigger chemical shifts observed for Zn LMM compared to Zn2p.

Interpretation of XPS spectra

Zn2p peak has significantly split spin-orbit components (Δ_metal=23eV).
ZnO has an unusual O1s spectrum with two peaks, possibly indicating either Zn(OH)₂, ZnCO₃,
or oxygen vacancies.
Zinc shows only a small binding energy shift in the Zn2p_3/2 region (1021eV - 1023eV, modal value).
- Peak width may broaden in the presence of more than one Zn species.
Zn2p peaks often accompanied by Auger peak at Kinetic Energy ~990eV.
- If zinc is buried (under carbon, for example), Zn Auger peak may be observed even if Zn2p is not (due to difference in electron kinetic energy).
- Similarly, Zn3p (very high kinetic energy) may be observed even if Zn2p is not.
Use X-ray induced Zn LMM Auger peaks, which have a larger shift with chemical state.
- Use Wagner plot to help assign chemistry.

General comments

There have been concerns about mobility of zinc in alloys and vapor pressure with concern about introducing zinc into a high-vacuum environment.
- In practice, this is not a major concern if the sample is not heated in vacuum.

About this element

Symbol: Zn
Date of discovery: 1746
Name origin: German zink
Appearance: blue-white
Discoverer: Andreas Marggraf
Obtained from: zinc blende, calamine

Melting point: 692 K
Boiling point: 1180 K
Density[kg/m³]: 7140
Molar volume: 9.16 × 10^-6 m³/mol
Protons/Electrons: 30
Neutrons: 35
Shell structure: 2,8,18,2
Electron configuration: [Ar]3d104s2
Oxidation state: 2,3
Crystal structure: hexagonal

Zinc alloys have been used for centuries; although, A. Marggraf is credited for the first isolation of zinc from the charcoal reduction of calamine in 1746. This bluish-white metal is brittle at ambient temperatures, but becomes malleable between 110–150°C. It is an essential element in the growth of plants and animals, and altered biological concentrations of zinc can lead to severe health problems. Zinc’s principle use is to galvanize iron and steel, preventing corrosion. It is also used to form numerous metal alloys such as brass, bronze, and aluminum solder. Zinc oxide is used in plastics, cosmetics, and wallpaper, while zinc sulfide is employed in luminescent dials, TV screens, and fluorescent lights.