Nitrogen

Nitrogen • Non-Metals

Primary XPS region: N1s
Overlapping regions: Ta4p_3/2, Mo3p_3/2, Cd3d_5/2Binding energies of common chemical states:

Chemical state	Binding energy Mg1s
Metal nitrides	~397 eV
NSi₃ (Si₃N₄)	398.0 eV
NSi₂O	399.9 eV
NSiO₂	402.5 eV
C-NH₂	~400 eV
Nitrate	>405 eV

Experimental information

The N1s region may be overlapped by peaks from tantalum, molybdenum, or cadmium.
- In the case of molybdenum, collect the full Mo3p / N1s region (370–455eV), making sure both Mo3p_3/2 and Mo3p_1/2 components are acquired.
- In the case of tantalum, it will be sufficient to collect only the Ta4p_3/2 / N1s region (370–450eV).
When analyzing nitrogen-containing hafnium compounds (e.g., nitrided hafnium silicate), the plasmon loss from the Hf4p_3/2 feature badly overlaps the N1s region.
- Acquire the N1s / Hf4p_3/2 region and the associated hafnium plasmon (365–410eV).
During sputter profiling, if nitrogen is observed when it should not be present, this probably indicates a leak in the argon supply.

Interpretation of XPS spectra

A variety of nitrogen bonding states may be observed as received silicon oxynitride samples.
- Higher binding energy states (with oxygen atoms substituted in place of silicon) are thermodynamically unstable^[1] (and are typically not observed for annealed silicon oxynitride samples).
- These states decay rapidly with Ar+ sputtering, even at low beam energies.
  - Sputter profiling cannot be used to depth-profile these states.
- Angle-resolved XPS is the appropriate method for identifying the depth distributions of the nitrogen chemical states.

N1s peak shapes for metal nitrides (e.g. TiN) can be complex and unusual, possibly with presence of surface oxynitrides.
- In the case of as received TiN, the oxidized nitride state in the N1s region is observed at lower binding energy compared to the pure nitride state.
  - Oxidation normally moves components to higher binding energy (e.g. NiSi₂O compared to NSi₃).

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Table of elements

N1s Spectra Received Sputter Cleaned TiN

The overlap between the N1s and Ta4p_3/2 region can be resolved with peak fitting.
- This will be necessary when analyzing TaN, for example.

Nitrogen-containing aromatic polymers (e.g., polyimide) may have weak π-π* satellite features shifted several eV from the main nitrogen peak.

General comments

N/A

References

[1] GM Rignanese et al., Phys. Rev. Lett. 79, 5174 (1997).

About this element

Symbol: N
Date of discovery: 1772
Name origin: Greek nitron genes
Appearance: colorless
Discoverer: Daniel Rutherford
Obtained from: liquid air

Melting point: 63.05 K
Boiling point: 77.36 K
Density[kg/m³]: 1.2506
Molar volume: 13.54 × 10^-6 m³/mol
Protons/Electrons: 7
Neutrons: 7
Shell structure: 2,5
Electron configuration: [He]2s22p3
Oxidation state: ±3,5,4,2
Crystal structure: hexagonal

As a crucial part of amino and nucleic acids, nitrogen is vital to all forms of life. It was discovered by Daniel Rutherford in 1772. However, compounds of nitrogen were recognized in the Middle Ages. The mixture of nitric and hydrochloric acids is able to dissolve gold. Normally a gas, nitrogen is colorless, odorless, and tasteless. Found abundantly, nitrogen constitutes 78% of Earth’s atmosphere. The largest commercial use of nitrogen is in the form of ammonia. Nitrogen also provides an inert atmosphere in tanks containing explosive liquids. Liquid nitrogen is a common cryogen, used for the preservation of bodies and reproductive cells and for the storage of biological samples.

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