Basic XPS Information Section

The Basic XPS Information Section provides fundamental XPS spectra, BE values, FWHM values, BE tables, overlays of key spectra, histograms and a table of XPS parameters.
The Advanced XPS Information Section is a collection of additional spectra, overlays of spectra, peak-fit advice, data collection guidance, material info,
common contaminants, degradation during analysis, auto-oxidation, gas capture study, valence band spectra, Auger spectra, and more.
Published literature references, and website links are summarized at the end of the advanced section.
→  Periodic Table – HomePage                          XPS Database of Polymers                    → Six (6) BE Tables

 

Nitrogen (N)

 

Frozen Nitrogen on Triton Moon – SN2 Nitratine – NaNO3 Liquid Nitrogen – LN2

 

  Page Index
  • Peak-fits and Overlays of N Chemical Compounds
  • Expert Knowledge Explanations


Nitrogen (N)

Peak-fits, BEs, FWHMs, and Peak Labels


Boron Nitride, BN
N (1s) Spectrum – raw
freshly exposed bulk
charge referenced so C (1s) = 285.0 eV
Boron Nitride, BN
N (1s) Spectrum – raw peak-fit
freshly exposed bulk
charge referenced so C (1s) = 285.0 eV

Boron Nitride, BN
B (1s) spectrum – raw
freshly exposed bulk
charge referenced so C (1s) = 285.0 eV
Boron Nitride, BN
  B (1s) spectrum – peak-fit
freshly exposed bulk
charge referenced so C (1s) = 285.0 eV
   
Boron Nitride, BN
Valence Band spectrum
freshly exposed bulk
charge referenced so C (1s) = 285.0 eV
 Boron Nitride, BN
C (1s) spectrum
freshly exposed bulk
charge referenced so C (1s) = 285.0 eV
 

 

Survey Spectrum of Boron Nitride, BN
with Peaks Integrated, Assigned and Labelled

→  Periodic Table 

XPS Signals for Nitrogen, (N)

Spin-Orbit Term,  BE (eV) Value, and Scofield σ for Aluminum Kα X-rays (1486 eV, 8.33 Ang)

Overlaps Spin-Orbit Term BE (eV) Value Scofield σ from 1486 eV X-rays IMFP (TPP-2M) in Å
Ta (4p) & Mo (3p) overlap N (1s) 398 1.80 29.2
Ga (3d) overlaps N (2s) 19 0.0065 37.1

σ:  abbreviation for the term Scofield Photoionization Cross-Section which is used with IMFP and TF to produce RSFs and atom% quantitation

Expected Bandgaps
Expected Bandgap for BN:  3.5 – 4.5 eV   (https://materialsproject.org)

*Scofield Cross-Section (σ) for C (1s) = 1.0

 

 

Energy Loss Peaks from N (1s) in BN
freshly cleaved ceramic

N (1s) – Extended Range Spectrum N (1s) – Extended Range Spectrum – Vertically Zoomed 


Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Side-by-Side Comparison of

Metal and Metal Nitrides of
Al, B, Fe, Ga, Ta, Ti
Peak-fits, BEs, FWHMs, and Overlays
    .
Aluminum metal, Alo
Al (2p) spectrum
Flood Gun OFF		 Aluminum Nitride, AlN
Al (2p) spectrum
Ion etched, Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 Overlay of Al (2p) Spectra 
from Alo metal and AlN
chemical shift:  +0.6 eV
    .
Boron, Bo
B (1s) spectrum
Flood Gun OFF
Ion Etched		 Boron Nitride, BN
B (1s) spectrum
Exposed bulk, light ion etch, Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 Overlay of B (1s) Spectra 
from Bo and BN
chemical shift:  +2.7 eV
    .
Iron, Feo
Fe (2p) spectrum
Flood Gun OFF		 Iron Nitride, FeN
Fe (2p) spectrum
Ion Etched, Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 Overlay of Fe (2p) Spectra 
from Feo and FeN
Chemical Shift:  +0.6 eV
     
Gallium, Gao
Ga (3d) spectrum
Flood Gun OFF		 Gallium Nitride, GaN
Ga (3d) spectrum
As received, not ion etched, Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 Overlay of Ga (3d) Spectra 
from Gao and GaN
Chemical Shift:  +1.0 eV
    .
Tantalum, Tao
Ta (4f) spectrum
Flood Gun OFF		 Tantalum Nitride, TaN
Ta (4f) spectrum
Ion etched, Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 Overlay of Ta (4f) Spectra 
from Tao and TaN
Chemical Shift:  +1.1 eV
Tantalum, Tao
Ta (4f) spectrum
Flood Gun OFF		 NOT ion etched, Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 NOT ion etched TaN
and ion etched Tao
    .
Titanium, Tio
Ti (2p) spectrum
Flood Gun OFF		 Titanium Nitride, TiN
Ti (2p) spectrum
Ion Etched, Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 Overlay of Ti (2p) Spectra 
from Tio and TiN
Chemical Shift:  +1.2 eV
    .
Titanium, Tio
Ti (2p) spectrum
Flood Gun OFF		 Titanium Nitride, TiN
Ti (2p) spectrum
As Received, NOT ion etched, Flood Gun ON		 Overlay of Ti (2p) Spectra 
from Tio and TiN as recd
Chemical Shift:  +1.7 eV
     
C (1s) after ion etch N (1s) after ion etch VB after ion etch
     

 

 

Nitrogen (N) in Ammonium Chloride, NH4Cl
Ammonium   NH4(+)
Peak-fits, BEs, FWHMs, and Peak Labels

Ammonium Chloride, NH4Cl
N (1s) Spectrum – raw
freshly crushed crystallites
charge referenced so C (1s) = 285.0 eV		 Ammonium Chloride, NH4Cl
N (1s) Spectrum – peak-fit
freshly crushed crystallites
charge referenced so C (1s) = 285.0 eV

Ammonium Chloride, NH4Cl
Cl (2p) Spectrum – raw
freshly crushed crystallites
charge referenced so C (1s) = 285.0 eV
Ammonium Chloride, NH4Cl
Cl (2p) Spectrum – peak-fit
freshly crushed crystallites
charge referenced so C (1s) = 285.0 eV
  .
Ammonium Chloride, NH4Cl
C (1s) Spectrum – peak-fit
freshly crushed crystallites
charge referenced so C (1s) = 285.0 eV		 Ammonium Chloride, NH4Cl
Valence Band Spectrum 
freshly crushed crystallites
charge referenced so C (1s) = 285.0 eV



Survey Spectrum of Ammonium Chloride, NH4Cl
with Peaks Integrated, Assigned and Labelled

Salammoniac – NH4Cl


 

 

Nitrogen (N) in Copper Nitrate
Cu(2+)   NO3(-)
Peak-fits, BEs, FWHMs, and Peak Labels

Cu(NO3)2 • 2H2O
N (1s) Spectrum – raw
freshly cleaved
charge referenced so C (1s) = 285.0 eV		 Cu(NO3)2 • 2H2O
N (1s) Spectrum – peak-fit
freshly cleaved
charge referenced so C (1s) = 285.0 eV
   
Cu(NO3)2 – 2H2O
Cu (2p) Spectrum – raw
freshly cleaved
charge referenced so C (1s) = 285.0 eV		 Cu(NO3)2 – 2H2O
Cu (2p) Spectrum – peak-fit
freshly cleaved
charge referenced so C (1s) = 285.0 eV
   
Cu(NO3)2 – 2H2O
O (1s) Spectrum – raw
freshly cleaved
charge referenced so C (1s) = 285.0 eV		 Cu(NO3)2 – 2H2O
O (1s) Spectrum – peak-fit
freshly cleaved
charge referenced so C (1s) = 285.0 eV
   
Cu(NO3)2 – 2H2O
Valence Band Spectrum 
freshly cleaved
charge referenced so C (1s) = 285.0 eV		 Cu(NO3)2 – 2H2O
C (1s) Spectrum – peak-fit
freshly cleaved
charge referenced so C (1s) = 285.0 eV

 

Survey Spectrum of Copper Nitrate, Cu(NO3)2-2H2O
with Peaks Integrated, Assigned and Labelled

 


Nitrogen (N) in Copper (1+) Cyanide (1-)

Cyanide Group,  CN(-)

Peak-fits, BEs, FWHMs, and Peak Labels

CuCN
N (1s) Spectrum – raw
pressed powder
charge referenced so C (1s) = 285.0 eV		 CuCN
N (1s) Spectrum – peak-fit
pressed powder
charge referenced so C (1s) = 285.0 eV
  .
CuCN
Cu (2p3/2) Spectrum – raw
pressed powder
charge referenced so C (1s) = 285.0 eV		 CuCN
Cu (2p3/2) Spectrum – peak-fit
pressed powder
charge referenced so C (1s) = 285.0 eV
  .
CuCN
C (1s) Spectrum – raw
pressed powder
charge referenced so C (1s) = 285.0 eV		 CuCN
C (1s) Spectrum – peak-fit
pressed powder
charge referenced so C (1s) = 285.0 eV

 

CuCN
Valence Band Spectrum 
pressed powder
charge referenced so C (1s) = 285.0 eV

  
 

 

Survey Spectrum of Copper Cyanide, CuCN
with Peaks Integrated, Assigned and Labelled

 

 

Nitrogen (N) in Kapton™
an Organic Poly-imide Polymer

Peak-fits, BEs, FWHMs, and Peak Labels
Kapton™
film wiped clean with hexanes
(wiping w IPA or scraping gives poor results)
Kapton
N (1s) Spectrum – raw
film wiped clean with hexanes
charge referenced so C (1s) = 285.0 eV		 Kapton
N (1s) Spectrum – peak-fit
film wiped clean with hexanes
charge referenced so C (1s) = 285.0 eV
 

Kapton
C (1s) Spectrum – raw 
film wiped clean with hexanes
charge referenced so C (1s) = 285.0 eV
Kapton
C (1s) Spectrum – peak-fit
film wiped clean with hexanes
charge referenced so C (1s) = 285.0 eV

Kapton
Valence Band Spectrum 
film wiped clean with hexanes
charge referenced so C (1s) = 285.0 eV
Kapton
O (1s) Chemical State Spectrum 
film wiped clean with hexanes
charge referenced so C (1s) = 285.0 eV
   

 

Survey Spectrum of Kapton™
with Peaks Integrated, Assigned and Labelled

Copyright ©:  The XPS Library 

→  Periodic Table 

 

Nitrate Minerals, Metal Nitrides, Crystals, and Chemical Compounds

 
Tasaregorodtsevite – N(CH3)4(AlSi5O12) Rakovanite – (NH4)3Na3(V10O28) · 12H2O Julienite – Na2[Co(SCN)4] · 8H2O  Darapskite – Na3(SO4)(NO3) · H2O 

 

 

 

Six (6) Chemical State Tables of N (1s) BEs

 

  • The XPS Library Spectra-Base
  • PHI Handbook
  • Thermo-Scientific Website
  • XPSfitting Website
  • Techdb Website
  • NIST Website

 

 

Notes of Caution when using Published BEs and BE Tables from Insulators and Conductors:

  • Accuracy of Published BEs
    • The accuracy depends on the calibration BEs used to calibrate the energy scale of the instrument.  Cu (2p3/2) BE can vary from 932.2 to 932.8 eV for old publications
    • Different authors use different BEs for the C (1s) BE of the hydrocarbons found in adventitious carbon that appears on all materials and samples.  From 284.2 to 285.3 eV
    • The accuracy depends on when the authors last checked or adjusted their energy scale to produce the expected calibration BEs
  • Worldwide Differences in Energy Scale calibrations
    • For various reasons authors still use older energy scale calibrations
    • Some authors still adjust their energy scale so Cu (2p3/2) appears at 932.2 eV or 932.8 eV because this is what the maker taught them
    • This range causes BEs in the higher BE end to be larger than expected
    • This variation increases significantly above 600 eV BE
  • Charge Compensation
    • Samples that behave as true insulators normally require the use of a charge neutralizer (electron flood gun with or without Ar+ ions) so that the measured chemical state spectra can be produced without peak-shape distortions or sloping tails on the low BE side of the peak envelop.
    • Floating all samples (conductive, semi-conductive, and non-conductive) and always using the electron flood gun is considered to produce more reliable BEs and is recommended.
  • Charge Referencing Methods for Insulators
    • Charge referencing is a common method, but it can produce results that are less reliable.
    • When an electron flood gun is used, the BE scale will usually shift to lower BE values by 0.01 to 5.0 eV depending on your voltage setting. Normally, to correct for this flood gun induced shift, the BE of the hydrocarbon C (1s) peak maximum from adventitious carbon is used to correct for the charge induced shift.
    • The hydrocarbon peak is normally the largest peak at the lowest BE.
    • Depending on your preference or training, the C (1s) BE assigned to this hydrocarbon peak varies from 284.8 to 285.0 eV.  Other BEs can be as low as 284.2 eV or as high as 285.3 eV
    • Native oxides that still show the pure metal can suffer differential charging that causes the C (1s) and the O (1s) and the Metal Oxide BE to be larger
    • When using the electron flood gun, the instrument operator should adjust the voltage and the XY position of the electron flood gun to produce peaks from a strong XPS signal (eg O (1s) or C (1s) having the most narrow FWHM and the lowest experimentally measured BE.

→  Periodic Table 

Table #1

N (1s) Chemical State BEs from:  “The XPS Library Spectra-Base”

C (1s) BE = 285.0 eV for TXL BEs
and C (1s) BE = 284.8 eV for NIST BEs

Element Atomic # Compound As-Measured by TXL or
NIST Average BE		 Largest BE Hydrocarbon C (1s) BE  Source
N 7 N-Ge 396.5 eV   285.0 eV The XPS Library
N 7 N-In 396.7 eV   285.0 eV The XPS Library
N 7 N-Zr 396.9 eV   285.0 eV The XPS Library
N 7 N-Cr 397.1 eV   285.0 eV The XPS Library
N 7 N-Si 397.1 eV 397.8 eV 285.0 eV The XPS Library
N 7 N-Nb 397.2 eV   285.0 eV The XPS Library
N 7 N-Ti 397.2 eV 397.5 eV 285.0 eV The XPS Library
N 7 N-V 397.2 eV   285.0 eV The XPS Library
N 7 Si3N4 (N*9) 397.4 eV 398.6 eV   Avg BE – NIST
N 7 N-Ga 397.5 eV   285.0 eV The XPS Library
N 7 N-Al 397.6 eV 398.0 eV 285.0 eV The XPS Library
N 7 N-Fe 397.7 eV   285.0 eV The XPS Library
N 7 N-W 397.7 eV 398.1 eV 285.0 eV The XPS Library
N 7 SiCN 398.0 eV   285.0 eV The XPS Library
N 7 KCN (N*3) 398.1 eV 399.6 eV   Avg BE – NIST
N 7 N-B 398.1 eV 398.3 eV 285.0 eV The XPS Library
N 7 N-B (N*6) 398.1 eV 398.4 eV   Avg BE – NIST
N 7 N-Ta 398.2 eV 398.3 eV 285.0 eV The XPS Library
N 7 NaN-N2 (N*4) 398.5 eV 400.1 eV   Avg BE – NIST
N 7 CuCN 398.7 eV   285.0 eV The XPS Library
N 7 N-C  amines     (R2NH2) 399.1 eV 400.2 eV 285.0 eV The XPS Library
N 7 N nitrile  (CN) PAN polymer 399.6 eV   285.0 eV The XPS Library
N 7 N-C=O 399.7 eV 400.0 eV 285.0 eV The XPS Library
N 7 NH4-Cl (N*3) 400.8 eV 401.7 eV   Avg BE – NIST
N 7 N-O 401.2 eV 402.4 eV 285.0 eV The XPS Library
N 7 (NH4)2-SO4 (N*1) 401.3 eV     One BE – NIST
N 7 NH4+,NR4+ 401.4 eV 402.4 eV 285.0 eV The XPS Library
N 7 Me4NCl (N*4) 401.5 eV 402.3 eV   Avg BE – NIST
N 7 NH4-NO3 (N*4) 401.9 eV 402.3 eV   Avg BE – NIST
N 7 NaN2-N (N*4) 402.8 eV 404.5 eV   Avg BE – NIST
N 7 M-NO2 (N*7) 403.3 eV 404.9 eV   Avg BE – NIST
N 7 N-O2  (nitrocellulose) 405.4 eV   285.0 eV The XPS Library
N 7 NO3-NH4 (N*4) 405.5 eV 407.3 eV   Avg BE – NIST
N 7 M-NO3 (N*14) 407.2 eV 408.1 eV   Avg BE – NIST
N 7 N-O3 408.2 eV   285.0 eV The XPS Library

 

Charge Referencing

  • (N*number) identifies the number of NIST BEs that were averaged to produce the BE in the middle column.
  • Binding Energy Scale calibration expects Cu (2p3/2) BE = 932.62 eV and Au (4f7/2) BE = 83.98 eV.  BE (eV) Uncertainty Range:  +/- 0.2 eV
  • Charge Referencing of insulators is defined such that the Adventitious Hydrocarbon C (1s) BE (eV) = 285.0 eV.  NIST uses C (1s) BE = 284.8 eV 
  • Note:   Ion etching removes adventitious carbon, implants Ar (+), changes conductivity of surface, and degrades chemistry of various chemical states.
  • Note:  Ion Etching changes BE of C (1s) hydrocarbon peak.
  • TXL – abbreviation for: “The XPS Library” (https://xpsLibrary.com).  NIST:  National Institute for Science and Technology (in USA)

→  Periodic Table 

Table #2

N (1s) Chemical State BEs from:  “PHI Handbook”

C (1s) BE = 284.8 eV

 

→  Periodic Table 

Copyright ©:  Ulvac-PHI

Table #3

N (1s) Chemical State BEs from:  “Thermo-Scientific” Website

C (1s) BE = 284.8 eV

Chemical state Binding energy N (1s) / eV
Metal nitrides ~397
NSi3 (Si3N4) 398.0
NSi2O 399.9
NSiO2 402.5
C-NH2 ~400
Nitrate >405

→  Periodic Table 

Copyright ©:  Thermo Scientific 

Table #4

N (1s) Chemical State BEs from:  “XPSfitting” Website

Chemical State BE Table derived by Averaging BEs in the NIST XPS database of BEs
C (1s) BE = 284.8 eV

 

 

→  Periodic Table 

Copyright ©:  Mark Beisinger

Table #5

N (1s) Chemical State BEs from:  “Techdb.podzone.net” Website

 

XPS Spectra – Chemical Shift | Binding Energy
C (1s) BE = 284.6 eV

 

XPS(X線光電子分光法)スペクトル 化学状態 化学シフト ケミカルシフト

Element Level Compound B.E.(eV) min   max
N 1s Nitride 397.3 ±1.1 396.2 ～ 398.3
N 1s Si3N4 397.5 ±0.4 397.1 ～ 397.8
N 1s BN 398.1 ±0.2 397.9 ～ 398.3
N 1s Azide (N*NN*) 398.4 ±0.5 397.9 ～ 398.8
N 1s Cyanides 398.9 ±1.5 397.4 ～ 400.3
N 1s NH3 399.2 ±0.5 398.7 ～ 399.7
N 1s Organic Matrix 399.9 ±1.1 398.8 ～ 401.0
N 1s Ammonium Salt 401.8 ±1.4 400.4 ～ 403.2
N 1s Azide (NN*N) 402.8 ±0.5 402.3 ～ 403.2
N 1s Nitrites 404.0 ±0.9 403.1 ～ 404.8
N 1s Nitrates 407.6 ±0.6 407.0 ～ 408.2

→  Periodic Table 

 

 

Histograms of NIST BEs for N (1s) BEs

Important Note:  NIST Database defines Adventitious Hydrocarbon C (1s) BE = 284.8 eV for all insulators.

 

Histogram indicates:  397.1 eV for pure TiN based on 9 literature BEs Histogram indicates:  397.8 eV for Si3N4 based on 30 literature BEs

Histogram indicates:  398.3 eV for pure BN based on 7 literature BEs Histogram indicates:  401.4 eV for pure NH4Cl based on 4 literature BEs

Histogram indicates:  404.2 eV for pure -NO2 based on 5 literature BEs Histogram indicates:  406.6 eV for pure -NO3 based on 6 literature BEs

 

 

Table #6


NIST Database of N (1s) Binding Energies

NIST Standard Reference Database 20, Version 4.1

Data compiled and evaluated
by
Alexander V. Naumkin, Anna Kraut-Vass, Stephen W. Gaarenstroom, and Cedric J. Powell
©2012 copyright by the U.S. Secretary of Commerce on behalf of the United States of America. All rights reserved.

Important Note:  NIST Database defines Adventitious Hydrocarbon C (1s) BE = 284.8 eV for all insulators.

 

 

To view the NIST table of BEs for N (1s) click on the link above.

→  Periodic Table 

 

 

Statistical Analysis of Binding Energies in NIST XPS Database of BEs

 

 

→  Periodic Table 

 

Advanced XPS Information Section

 

Expert Knowledge, Spectra, Features, Guidance and Cautions
for XPS Research Studies on Nitrogen-containing Materials

 

 

 

Expert Knowledge Explanations

 

Overlay reveals shift Shake-up Example Auger signal overlaps X

 

 

 

Lithium Nitride, Li3N
fresh powder, reacted to air during mounting
Survey Spectrum from Lithium Nitride, Li3N
Flood gun is ON, C (1s) BE = 285.0 eV
fresh powder		 N (1s) Chemical State Spectrum from Lithium Nitride, Li3N
Flood gun is ON, C (1s) BE = 285.0 eV
fresh powder
   .
C (1s) Chemical State Spectrum from Lithium Nitride, Li3N
Flood gun is ON, C (1s) BE = 285.0 eV
fresh powder		 Li (1s) Chemical State Spectrum from Lithium Nitride, Li3N
Flood gun is ON, C (1s) BE = 285.0 eV
fresh powder
   .
   O (1s) from Lithium Nitride, Li3N
Flood gun is ON, C (1s) BE = 285.0 eV
fresh powder
 

 

Silicon Nitride, Si3N4
Low pressure CVD
As Received Surface of Coated Wafer
Survey Spectrum from Silicon Nitride, Si3N4 (LPCVD)
Flood gun is ON, C (1s) BE = 285.0 eV
As received surface of coated wafer		 N (1s) Chemical State Spectrum from Silicon Nitride, Si3N4 (LPCVD)
Flood gun is ON, C (1s) BE = 285.0 eV
As received surface of coated wafer
  . 
C (1s) Chemical State Spectrum from Silicon Nitride, Si3N4 (LPCVD)
Flood gun is ON, C (1s) BE = 285.0 eV
As received surface of coated wafer		 Si (2p) Chemical State Spectrum from Silicon Nitride, Si3N4 (LPCVD)
Flood gun is ON, C (1s) BE = 285.0 eV
As received surface of coated wafer
  . 
Valence Band Spectrum from Silicon Nitride, Si3N4 (LPCVD)
Flood gun is ON, C (1s) BE = 285.0 eV
As received surface of coated wafer		  N (1s) Loss Peaks Spectrum from Silicon Nitride, Si3N4 (LPCVD)
Flood gun is ON, C (1s) BE = 285.0 eV
As received surface of coated wafer

 

Quantitation

 

Quantitation Details and Information

 

Quantitation by XPS is often incorrectly done, in many laboratories, by integrating only the main peak, ignoring the Electron Loss peak, and the satellites that appear as much as 30 eV above the main peak.  By ignoring the electron loss peak and the satellites, the accuracy of the atom% quantitation is in error.

When using theoretically calculated Scofield cross-section values, the data must be corrected for the transmission function effect, use the calculated TPP-2M IMFP values, the pass energy effect on the transmission function, and the peak area used for calculation must include the electron loss peak area, shake-up peak area, multiplet-splitting peak area, and satellites that occur within 30 eV of the main peak.

 

Quantitation from Pure, Homogeneous Binary Compound
composed of Nitrogen

 

This section is focused on measuring and reporting the atom % quantitation that results by using:

  • Scofield cross-sections,
  • Spectra corrected to be free from Transmission Function effects
  • A Pass Energy that does not saturate the detector system in the low KE range (BE = 1000-1400 eV)
  • A focused beam of X-ray smaller than the field of view of the lens
  • An angle between the lens and the source that is ~55 deg that negates the effects of beta-asymmetry
  • TPP-2M inelastic mean free path values, and
  • Either a linear background or an iterated Shirley (Sherwood-Proctor) background to define peak areas

The results show here are examples of a method being developed that is expected to improve the “accuracy” or “reliability” of the atom % values produced by XPS.

Copyright ©:  The XPS Library 

 

 

XPS Facts, Guidance & Information

→  Periodic Table 

    Element   Nitrogen (N)
  
    Primary XPS peak used for Peak-fitting :   N (1s)  
    Spin-Orbit (S-O) splitting for Primary Peak:   NO Spin-Orbit splitting for “s” orbitals.
  
    Binding Energy (BE) of Primary XPS Signal:   399 eV
  
    Scofield Cross-Section (σ) Value:   N (1s) = 1.800
  
    Conductivity:      
    Range of N (1s) Chemical State BEs:   396 – 408 eV range  
    Signals from other elements that overlap
N (1s) Primary Peak:		      
    Bulk Plasmons:   ~xxx eV above peak max for pure  
    Shake-up Peaks:   ??  
    Multiplet Splitting Peaks:   not possible  

 

 

 General Information about
Nitrogen Compounds:		   xx  
    Cautions – Chemical Poison Warning  

xx 

  

Copyright ©:  The XPS Library 

 

Information Useful for Peak-fitting N (1s)

 

  • FWHM (eV) of N (1s) in BN :  ~1.2 eV using 25 eV Pass Energy after ion etching:
  • FWHM (eV) of N (1s) in NO3  ~1.6 eV using 50 eV Pass Energy  (before ion etching)
  • Binding Energy (BE) of Primary Signal used for Measuring Chemical State Spectra:  399 eV for N (1s) in Metals with +/- 0.2 uncertainty
  • List of XPS Peaks that can Overlap Peak-fit results for N (1s):  xx

→  Periodic Table 

 

General Guidelines for Peak-fitting XPS Signals

 

  • Typical Energy Resolution for Pass Energy (PE) setting used to measure Chemical State Spectra on Various XPS Instruments
    • Ag (3d5/2) FWHM (eV) = ~0.95 eV for PE 50 on Thermo K-Alpha
    • Ag (3d5/2) FWHM (eV) = ~1.00 eV for PE 80 on Kratos Nova
    • Ag (3d5/2) FWHM (eV) = ~0.95 eV for PE 45 on PHI VersaProbe
  • FWHM (eV) of Pure Elements: Ranges from 0.4 to 1.0 eV across the periodic table
  • FWHM of Chemical State Peaks in any Chemical Compound:  Ranges from 1.1 to 1.6 eV  (in rare cases FWHM can be 1.8 to 2.0 eV)
  • FWHM of Pure Element versus FWHM of Oxide:  Pure element FWHM << Oxide FWHM  (e.g. 0.8 vs 1.5 eV, roughly 2x)
  • If FWHM Greater than 1.6 eV:  When a peak FWHM is larger than 1.6 eV, it is best to add another peak to the peak-fit envelop.
  • BE (eV) Difference in Chemical States: The difference in chemical state BEs is typically 1.0-1.3 eV apart.  In rare cases, <0.8 eV.
  • Number of Peaks to Use:  Use minimum. Do not use peaks with FWHM < 1.0 eV unless it is a or a conductive compound.
  • Typical Peak-Shape:  80% G: 20% L,   or Voigt : 1.4 eV Gaussian and 0.5 eV Lorentzian
  • Spin-Orbit Splitting of Two Peaks (due to Coupling):  The ratio of the two (2) peak areas must be constrained.
  • Constraints used on Peak-fitting: typically constrain the peak area ratios based on the Scofield cross-section values
  • Asymmetry for Conductive materials:  20-30% with increased Lorentzian %
  • Peak-fitting “2s” or “3s” Peaks:  Often need to use 50-60% Lorentzian peak-shape
  • Notes:
    • Other Oxidation States can appear as small peaks when peak-fitting
    • Pure element signals normally have asymmetric tails that should be included in the peak-fit.
    • Gaseous state materials often display asymmetric tails due to vibrational broadening.
    • Peak-fits of C (1s) in polymers include an asymmetric tail when the energy resolution is very high.
    • Binding energy shifts of some compounds are negative due to unusual electron polarization.

→  Periodic Table 

 

Contaminants Specific to Metal Nitrides

 

  • METAL Nitride thin films often have a low level of iron (Fe) in the bulk as a contaminant or to strengthen the thin film
  • METAL Nitride degrades slightly when the surface is ion etched inside the analysis chamber

 

Commonplace Contaminants

 

  • Carbon and Oxygen are common contaminants that appear on nearly all surfaces. The amount of Carbon usually depends on handling.
  • Carbon is usually the major contaminant.  The amount of carbon ranges from 5-50 atom%.
  • Carbon contamination is attributed to air-borne organic gases that become trapped by the surface, oils transferred to the surface from packaging containers, static electricity, or handling of the product in the production environment.
  • Carbon contamination is normally a mixture of different chemical states of carbon (hydrocarbon, alcohol or ether, and ester or acid).
  • Hydrocarbon is the dominant form of carbon contamination. It is normally 2-4x larger than the other chemical states of carbon.
  • Carbonate peaks, if they appear, normally appear ~4.5 eV above the hydrocarbon C (1s) peak max BE.
  • Low levels of carbonate is common on many s that readily oxidize in the air.
  • High levels of carbonate appear on reactive oxides and various hydroxides.  This is due to reaction between the oxide and CO2 in the air.
  • Hydroxide contamination peak is due to the reaction with residual water in the lab air or the vacuum.
  • The O (1s) BE of the hydroxide (water) contamination normally appears 0.5 to 1.0 eV above the oxide peak
  • Sodium (Na), Potassium (K), Nitrogen (N) and Nitrogen (Cl) are common trace to low level contaminants
  • To find low level contaminants it is very useful to vertically expand the 0-600 eV region of the survey spectrum by 5-10X
  • A tiny peak that has 3 or more adjacent data-points above the average noise of the background is considerate to be a real peak
  • Carbides can appear after ion etching various reactive s.  Carbides form due to the residual CO and CH4 in the vacuum.
  • Ion etching can produce low oxidation states of the material being analyzed.  These are newly formed contaminants.
  • Ion etching polymers by using standard Ar+ ion guns will destroy the polymer, converting it into a graphitic type of carbon

→  Periodic Table 

 

Data Collection Guidance

 

  • Chemical state differentiation can be difficult
  • Collect principal N (1s) peak
  • Long time exposures (high dose) to X-rays can degrade various polymers, catalysts, high oxidation state compounds
  • During XPS analysis, water or solvents can be lost due to high vacuum or irradiation with X-rays or Electron flood gun
  • Auger signals can sometimes be used to discern chemical state shifts when XPS shifts are very small

→  Periodic Table 

 

Data Collection Settings for Metal Nitride (N)

 

  • Conductivity:  Metal Nitrides do not readily develops a native oxide that is sensitive to Flood Gun.
  • Primary Peak (XPS Signal) used to measure Chemical State Spectra:  N (1s) at 399 eV
  • Recommended Pass Energy for Measuring Chemical State Spectrum:  25-50 eV    (Produces Ag (3d5/2) FWHM ~0.7 eV)
  • Recommended # of Scans for Measuring Chemical State Spectrum:  4-5 scans normally   (Use 10-25 scans to improve S/N)
  • Dwell Time:  50 msec/point
  • Step Size:  0.1 eV/point   (0.1 eV/step or 0.1 eV/channel)
  • Standard BE Range for Measuring Chemical State Spectrum:   380 – 410 eV
  • Recommended Extended BE Range for Measuring Chemical State Spectrum:  380 – 460 eV
  • Recommended BE Range for Survey Spectrum:  -10 to 1,100 eV   (above 1,100 eV there are no useful XPS signals, except for Ge and Ga)
  • Typical Time for Survey Spectrum:  3-5 minutes for newer instruments, 5-10 minutes for older instruments
  • Typical Time for a single Chemical State Spectrum with high S/N:  5-10 minutes for newer instruments, 10-15 minutes for older instruments 

→  Periodic Table 

 

Effects of Argon Ion Etching

  • Carbides appear after ion etching metals and various reactive surfaces.  Carbides form due to the residual CO and CH4 in the vacuum.
  • Ion etching can produce low oxidation states of the material being analyzed.  These are newly formed contaminants.
  • Ion etching polymers by using standard Ar+ ion guns will destroy the polymer, converting it into a graphitic type of carbon

→  Periodic Table 

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Gas Phase XPS or UPS Spectra
 
 
     
     
     
     
     
     
     
     
     
 
 

 

Chemical State Spectra from Literature

from Thermo Scientific Website

 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

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