Tao Ta2O5 TaS2 TaSix TaC TaN TaF5 LiTaO4

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

 

Tantalum (Ta)

 

Tantalcarbide – TaC Tantalum – Tao Tantalite – MnTa2O6

 

  Page Index
  • Expert Examples & Explanations



Tantalum (Tao) Metal

Peak-fits, BEs, FWHMs, and Peak Labels

  .
Tantalum (Ta) Metal
Ta (4f) Spectrum – raw spectrum
ion etched clean		 Tantalum (Ta) Metal
Peak-fit of Ta (4f) Spectrum
w/o asymm
→  Periodic Table – HomePage  
Tantalum (Ta) Metal
Ta (4f) Spectrum – extended range 
 Tantalum (Ta) Metal
Peak-fit of Ta (4f) Spectrum (w asymm)
 

.
Tantalum (Ta) Metal
Ta (4d) Spectrum		 Tantalum (Ta) Metal
 Ta (5p) Spectrum
   
 


Survey Spectrum of Tantalum (Tao) Metal
with Peaks Integrated, Assigned and Labelled

 
→  Periodic Table 

XPS Signals for Tantalum, Tao Metal

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 (4s) 563 1.79 16.4
Ta (4p1/2) 462 2.06 18.4
N (1s) overlaps Ta (4p3/2) 400 5.02 18.4
Ta (4d3/2) 238 6.40 20.6
Ta (4d5/2) 226 9.24 20.6
F (2s) overlaps Ta (4f5/2) 23.65 3.80 23.0
O (2s) overlaps Ta (4f7/2) 21.74 4.82 23.0
Ta (5s) 68 0.363 22.5
Ta (5p1/2) 43 0.346 22.9
Ta (5p3/2) 33 0.754 22.9

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

Plasmon Peaks

Auger Peaks

Energy Loss    Intrinsic Plasmon Peak:  ~xx eV above peak max
Expected Bandgap for Ta2O5: ~4 eV
Work Function for Ta:  xx eV

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

→  Periodic Table 

 

Valence Band Spectrum from Tao Metal
 Fresh exposed bulk produced by extensive Ar+ ion etching


Plasmon Peaks from Tao Metal
 Fresh exposed bulk produced by extensive Ar+ ion etching

Ta (4f) – Extended Range Spectrum Ta (4f) – Extended Range Spectrum – Vertically Zoomed
→  Periodic Table 
 

Ta (MMN) Auger Peaks from Tao Metal
 Fresh exposed bulk produced by extensive Ar+ ion etching
Tao Metal – main Auger peak Ta Metal – full Auger range
 

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 
 

Artefacts Caused by Argon Ion Etching

C (1s) from Tantalum Carbide(s)

can form when ion etched Reactive Metal Surfaces capture
Residual UHV Gases (CO, H2O, CH4 etc)

Argon Trapped in Tao

can form when Argon Ions are used
to removed surface contamination
 na
overlap with Ta 4d
 

Side-by-Side Comparison of

Ta Native Oxide & Tantalum Pentoxide (Ta2O5)
Peak-fits, BEs, FWHMs, and Peak Labels
Ta Native Oxide Ta2O5
Ta (4f) from Ta Native Oxide
Flood Gun OFF
As-Measured, C (1s) at 285.1 eV 		 Ta (4f) from Ta2O5 – pressed pellet
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV
→  Periodic Table 
  .
Ta Native Oxide Ta2O5
C (1s) from Ta Native Oxide
As-Measured, C (1s) at 285.1 eV
Flood Gun OFF

C (1s) from Ta2O5 – pressed pellet
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV

→  Periodic Table 
  .
Ta Native Oxide Ta2O5
O (1s) from Ta Native Oxide
As-Measured, C (1s) at 285.1 eV (Flood Gun OFF)

O (1s) from Ta2O5 – pressed pellet
Flood Gun ON, Charge Referenced to C (1s) at 285.0 eV

 
→  Periodic Table

 

 

 

Survey Spectrum of Tantalum Pentoxide, Ta2O5
with Peaks Integrated, Assigned and Labelled

→  Periodic Table  

Overlays of Ta (4f) Spectra for
Ta Native Oxide and Ta2O5

Caution: BEs from Grounded Native Oxides can be Misleading

 Overlay of Tao metal and Ta Native Oxide – Ta (4f)
Native Oxide C (1s) = 285.1  (Flood gun OFF)

  Overlay of Tao metal and Ta2O5 – Ta (4f)
Pure Oxide C (1s) = 285.0 eV
Chemical Shift: 4.4 eV
 
→  Periodic Table  Copyright ©:  The XPS Library 

 

Overlay of Ta (4f) 
Tao Metal, Ta Native Oxide, & Ta2O5 

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Valence Band Spectra
Tao, Ta2O5 

Tao
Ion etched clean		 Ta2O5 – pressed pellet
Flood gun is ON,  Charge referenced so C (1s) = 285.0 eV

Overlay of Valence Band Spectra
for Tao metal and Ta2O5

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Tantalum Minerals, Gemstones, and Chemical Compounds

 
Aluminotantite – AlTaO4 Wodginite – MnSnTa2O8 Lithiotantite – LiTa3O8  Liandratite – UTa2O8

→  Periodic Table 

 

Six (6) Chemical State Tables of Ta (4f7/2) BEs

 

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

→  Periodic Table 

 

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 between 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

Ta (4f7/2) 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
Ta 73 Ta  – element 21.8 eV 285.0 eV The XPS Library
Ta 73 TaSi2 (N*1) 22.3 eV 284.8 eV Avg BE – NIST
Ta 73 Ta-N 22.8 eV 23.2 eV 285.0 eV The XPS Library
Ta 73 Ta-N0.28 (N*1) 22.8 eV 284.8 eV Avg BE – NIST
Ta 73 CoTaZr 23.2 eV 285.0 eV The XPS Library
Ta 73 Ta-C 23.2 eV 23.9 eV 285.0 eV The XPS Library
Ta 73 TaS2 23.5 eV 285.0 eV The XPS Library
Ta 73 KTaO3 (N*1) 25.9 eV 284.8 eV Avg BE – NIST
Ta 73 Ta-2O5 26.5 eV 27.1 eV 285.0 eV The XPS Library
Ta 73 Ta2O5 (N*4) 26.5 eV 26.9 eV 284.8 eV Avg BE – NIST
Ta 73 Ta-Br5 (N*1) 26.9 eV 284.8 eV Avg BE – NIST
Ta 73 Ta-Cl5 (N*1) 27.3 eV 284.8 eV Avg BE – NIST
Ta 73 Ta-F5 (N*1) 27.8 eV 284.8 eV Avg BE – NIST
Ta 73 Ta-F3 28.3 eV 285.0 eV The XPS Library
Ta 73 Ta-F5 29.3 eV 285.0 eV The XPS Library

Charge Referencing Notes

  • (N*number) identifies the number of NIST BEs that were averaged to produce the BE in the middle column.
  • The XPS Library uses Binding Energy Scale Calibration with 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

Ta (4f7/2) Chemical State BEs from:  “PHI Handbook”

C (1s) BE = 284.8 eV

→  Periodic Table 

Copyright ©:  Ulvac-PHI

Table #3

Ta (4f7/2) Chemical State BEs from:  “Thermo-Scientific” Website

C (1s) BE = 284.8 eV

Chemical state Binding energy (eV),
Ta (4f7/2)
Ta metal 21.8
TaN 23.0
Ta2O5 26.2

→  Periodic Table 

Copyright ©:  Thermo Scientific 

Table #4

Ta (4f7/2) 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

Ta (4f7/2) 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
Ta 4f7/2 Ta 21.8 ±0.3 21.5 ～ 22.0
Ta 4f7/2 Cl6(Ta6Cl12)(Et4N)2 26.2 ±0.2 26.0 ～ 26.4
Ta 4f7/2 Br6(Ta6Cl12)(Bu4N)2 26.3 ±0.3 26.0 ～ 26.5
Ta 4f7/2 TaS 26.6 ±0.3 26.3 ～ 26.8
Ta 4f7/2 TaS2 26.7 ±0.3 26.4 ～ 26.9
Ta 4f7/2 Ta2O5 26.7 ±0.3 26.4 ～ 26.9
Ta 4f7/2 Halides 27.4 ±0.5 26.9 ～ 27.9

 

→  Periodic Table 

 


Histograms of NIST BEs for Ta (4f7/2) BEs

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

 

Histogram indicates:  21.7 eV for Ta metal based on 9 literature BEs Histogram indicates:  26.7 eV for Ta2O5 based on 4 literature BEs

Table #6


NIST Database of Ta (4f7/2) 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.

 

Element Spectral Line Formula Energy (eV) Reference
Ta 4f7/2 Ta 21.60  Click
Ta 4f7/2 Ta 21.60  Click
Ta 4f7/2 Ta 21.60  Click
Ta 4f7/2 Ta 21.61  Click
Ta 4f7/2 Ta 21.62  Click
Ta 4f7/2 Ta 21.64  Click
Ta 4f7/2 Ta 21.70  Click
Ta 4f7/2 Ta 21.70  Click
Ta 4f7/2 Ta 21.80  Click
Ta 4f7/2 Ta 21.90  Click
Ta 4f7/2 Ta 21.90  Click
Ta 4f7/2 Ta 21.90  Click
Ta 4f7/2 Ta 21.90  Click
Ta 4f7/2 Ta 22.00  Click
Ta 4f7/2 TaSi2 22.30  Click
Ta 4f7/2 TaN0.07 22.50  Click
Ta 4f7/2 Ta0.4N0.5 22.80  Click
Ta 4f7/2 TaN0.28 22.85  Click
Ta 4f7/2 Ta2N 22.85  Click
Ta 4f7/2 TaS2 22.90  Click
Ta 4f7/2 TaC0.95 22.90  Click
Ta 4f7/2 Ta2C 23.08  Click
Ta 4f7/2 (PbS)1.13TaS2 23.10  Click
Ta 4f7/2 (PbS)1.14(TaS2)2 23.10  Click
Ta 4f7/2 (SnS)1.16TaS2 23.10  Click
Ta 4f7/2 Ta4C3 23.11  Click
Ta 4f7/2 TaC0.75 23.25  Click
Ta 4f7/2 Ta3C2 23.26  Click
Ta 4f7/2 TaC0.95 23.50  Click
Ta 4f7/2 O2/TaC0.95 23.50  Click
Ta 4f7/2 TaC0.98 23.55  Click
Ta 4f7/2 TaS2 23.60  Click
Ta 4f7/2 Ta3N5 24.20  Click
Ta 4f7/2 NaTaO3 25.70  Click
Ta 4f7/2 NaTaO3 25.70  Click
Ta 4f7/2 [Ta6Cl12(H2O)4]Cl2.4H2O 25.80  Click
Ta 4f7/2 RhTaO4 25.80  Click
Ta 4f7/2 KTaO3 25.90  Click
Ta 4f7/2 Ta2O5 26.00  Click
Ta 4f7/2 Ta2O5 26.00  Click
Ta 4f7/2 [N(C2H5)4]2[Ta6Cl12Cl6] 26.20  Click
Ta 4f7/2 [N(C4H9)4]2[Ta6Cl12Br6] 26.30  Click
Ta 4f7/2 Ta2O5/Si 26.40  Click
Ta 4f7/2 Ta2O5 26.50  Click
Ta 4f7/2 Ta2O5 26.60  Click
Ta 4f7/2 TaS 26.60  Click
Ta 4f7/2 TaS2 26.70  Click
Ta 4f7/2 Ta2O5/Si 26.80  Click
Ta 4f7/2 TaBr5 26.90  Click
Ta 4f7/2 Ta2O5 26.90  Click
Ta 4f7/2 Ta2O5 26.90  Click
Ta 4f7/2 Ta2O5/Si 26.90  Click
Ta 4f7/2 TaSi2 27.00  Click
Ta 4f7/2 TaOx 27.00  Click
Ta 4f7/2 Ta2O5 27.00  Click
Ta 4f7/2 Ta2O5/Ta2N 27.05  Click
Ta 4f7/2 Ta2O5/Ta2N 27.05  Click
Ta 4f7/2 TaCl5 27.30  Click
Ta 4f7/2 TaSi2Ox 27.50  Click
Ta 4f7/2 TaF5 27.80  Click
Ta 4f7/2 K2TaF7 29.40  Click

 

 

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 Tantalum Materials

 

 

 

Expert Knowledge Examples & Explanations

→  Periodic Table 

 

 

Tantalum Chemical Compounds

 

Peak-fits and Overlays of Chemical State Spectra

Pure Tantalum, Tao:  Ta (4f)
Cu (2p3/2) BE = 932.6 eV		 Ta2O5:  Ta (4f)
C (1s) BE = 285.0 eV		 TaF3: Ta (4f)
C (1s) BE = 285.0 eV

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Overlay of Ta (4f) Spectra shown Above

C (1s) BE = 285.0 eV

 

Chemical Shift between Ta and Ta2O5:  4.4 eV
 Chemical Shift between Ta and TaF5:   6.7 eV

 

→  Periodic Table 

 


Tantalum Oxide (Ta2O5)
pressed powder

Survey Spectrum from Ta2O5
Flood gun is ON, C (1s) BE = 285.0 eV
 Ta (4f) Chemical State Spectrum from Ta2O5
Flood gun is ON, C (1s) BE = 285.0 eV
  .
O (1s) Chemical State Spectrum from Ta2O5
Flood gun is ON, C (1s) BE = 285.0 eV
 C (1s) Chemical State Spectrum from Ta2O5
Flood gun is ON, C (1s) BE = 285.0 eV
  .
Valence Band Spectrum from Ta2O5
Flood gun is ON, C (1s) BE = 285.0 eV
 Auger Signals from Ta2O5
Flood gun is ON, C (1s) BE = 285.0 eV
na


Shake-up Features
for Ta2O5

Ta (4f)

 

→  Periodic Table 

 

 

Tantalum Chemical Compounds

 

Tantalum Pentafluoride, TaF5
(Danger: sublimes in vacuum and degrades)

Survey Ta (4f)
  . 
C (1s) F (1s)
.
Valence Band

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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 Tantalum – Ta2O5

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.

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Flood Gun Effect on Native Oxide of Tantalum

 

Native Oxide of Tantalum Sheet – Sample GROUNDED

 

 

Native Oxide of Tantalum Sheet – Sample Grounded

Electron Flood Gun:  0 Voltage (FG OFF), Min Voltage versus Max Voltage

Ta (4f) O (1s) C (1s)
→  Periodic Table 

 


XPS Study of UHV Gas Captured by Freshly Ion Etched Tantalum
Reveals Chemical Shifts and Chemical States that Develop from Highly Reactive Pure Ta

Surface was strongly Ar+ ion etched to remove all contaminants, and
then allowed to react overnight with the UHV Gases – CO, H2, H2O, O2 & CH4
that normally reside inside on the walls of the chamber, on the sample stage,
and on the nearby un-etched surface a total of 10-14 hours.  UHV pump was a Cryopump.
Initial spectra are at the front.  Final spectra are at the rear. Flood gun is OFF.
Ta (4f) Signal
  O (1s) Signal C (1s) Signal
Copyright ©:  The XPS Library

 


AES Study of UHV Gas Captured by Freshly Ion Etched Tantalum

Tantalum sheet was ion etched and allowed to react with residual UHV gases overnight – ~14 hr run.

Ta (MNN) Signal:
Ta at front -> Ta2O5x at rear 
Ta KE = 1670.1 eV		 O (KLL) Signal:
Ta at front -> Ta2O5x at rear 
O KE = 507.3 eV		 C (KLL) Signal:
Ta at front -> Ta2O5x at rear 
O KE = 266.3 eV
   
     
 
 

Auger Chemical State Spectra from Ta2O5 using Charge Control Conditions
 
Ta (MNN) Signal:
Ta2O5 w charge control – Hemi-sphere (HSA) – 10 kV
High Energy Resolution Mode for Chemical States		 O (KLL) Signal:
Ta2O5 w charge control – Hemi-sphere (HSA) – 10 kV
High Energy Resolution Mode for Chemical States
 C (KLL) Signal:
Ta2O5 w charge control – Hemi-sphere (HSA) – 10 kV
High Energy Resolution Mode for Chemical States
     

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

 

Tantalum Alloys

   
XxCu XxCu
→  Periodic Table   
XxCu XxCu

 

Copyright ©:  The XPS Library 

 

 

 

XPS Facts, Guidance & Information

→  Periodic Table 

    Element Tantalum (Ta)
  
    Primary XPS peak used for Peak-fitting: Ta (4f7/2)  
    Spin-Orbit (S-O) splitting for Primary Peak: Spin-Orbit splitting for “f” orbital,  ΔBE = 1.9 eV
  
    Binding Energy (BE) of Primary XPS Signal: 21.8 eV
  
    Scofield Cross-Section (σ) Value: Ta (4f7/2) = 4.82    Ta (4f5/2) = 3.80
  
    Conductivity: Ta resistivity =  
Native Oxide suffers Differential Charing		  
    Range of Ta (4f7/2) Chemical State BEs: 21 – 28 eV range   (Ta to TaF5)  
Signals from other elements that overlap
Ta (4f7/2) Primary Peak:		   xx (xx)
Bulk Plasmons:   ~xx eV above peak max for pure
Shake-up Peaks: xx
Multiplet Splitting Peaks:   xx

 

 

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

xx 

Copyright ©:  The XPS Library 

→  Periodic Table 

 

Information Useful for Peak-fitting Ta (4f7/2)

  • FWHM (eV) of Ta (4f7/2) for Pure Tao :  ~0.6 eV using 25 eV Pass Energy after ion etching
  • FWHM (eV) of Ta (4f7/2) for Ta2O5:  ~1.1 eV using 50 eV Pass Energy  (before ion etching)
  • Binding Energy (BE) of Primary Signal used for Measuring Chemical State Spectra:  21.8 eV for Ta (4f7/2) with +/- 0.2 uncertainty
  • List of XPS Peaks that can Overlap Peak-fit results for Ta (4f7/2):  xxx

→  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) = ~0.90 eV for PE 50 on Thermo K-Alpha
    • Ag (3d5/2) FWHM (eV) = ~0.95 eV for PE 80 on Kratos Nova
    • Ag (3d5/2) FWHM (eV) = ~0.95 eV for PE 45 on PHI VersaProbe
    • Ag (3d5/2) FWHM (eV) = ~0.85 eV for PE 50 on SSI S-Probe
  • 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 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.

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 a very few compounds are negative due to unusual electron polarization.

→  Periodic Table 

 

Contaminants Specific to Tantalum

  • Tantalum develops a thick native oxide due to the reactive nature of clean Tantalum.
  • The native oxide of Ta2O5x is 4-6 nm thick.
  • Tantalum thin films can have a low level of iron (Fe) in the bulk as a contaminant or due to sputter coater shields
  • Tantalum forms a low level of carbide when the surface is argon 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), Sulfur (S) and Chlorine (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. The BE for C (1s) is a useful guide.  It is not absolute. Chemical shifts from native oxides can be erroneous.
  • Collect spectra from the valence band, and the principal Ta (4f7/2) peak.  Auger peaks are sometimes used to decide chemical state assignments.
  • Long time exposures (high dose) to X-rays can degrade various polymers, catalysts, and 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 are sometimes used to discern chemical states when XPS shifts are very small. Auger shifts can be larger than XPS shifts.

→  Periodic Table 

 

Data Collection Settings for Tantalum (Ta)

  • Conductivity:  Tantalum readily develops a native oxide that is sensitive to Flood Gun – Differential Charging Possible – float sample recommended
  • Primary Peak (XPS Signal) used to measure Chemical State Spectra:  Ta (4f7/2) at 21.8 eV
  • Recommended Pass Energy for Measuring Chemical State Spectrum:  40-50 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:  15 – 35 eV
  • Recommended Extended BE Range for Measuring Chemical State Spectrum:  10 – 100 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, As, 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 Ta and various reactive surfaces.  Carbides form due to the presence of 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 

Copyright ©:  The XPS Library 
Gas Phase XPS or UPS Spectra

 

Chemical State Spectra from Literature
From Thermo Website

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