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

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Titanium (Ti)

 

Ilmenite – FeTiO3	Titanium – Tio	Rutile – TiO2

 

Page Index
Pure Element Spectra with Peak-fits IMFP and Cross-sections for Pure Element Native Oxide Spectra with Peak-fits Pure Oxide Spectra with Peak-fits	Overlays and Valence Band Spectra Six (6) Tables of Chemical State BEs  Histograms of NIST BEs Advanced XPS Information Section	Peak-fits and Overlays of Ti Chemical Compounds Quantitation and Atom %s Flood Gun Effects on Native Oxide Spectra Study of UHV Gas Capture after Cleaning	Auger Peaks and Spectra Contamination XPS Facts, Guidance, Information Chemical State Spectra from Literature

• Expert Knowledge & Explanations

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Titanium (Ti^o) Metal
Peak-fits, BEs, FWHMs, and Peak Labels

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Titanium (Tio) Metal Ti (2p) Spectrum – raw spectrum ion etched clean	Titanium (Tio) Metal Peak-fit of Ti (2p) Spectrum (w/o asymm) using 2p3/2 to 2p1/2 peak area ratio for peak-fit
→  Periodic Table – HomePage
Titanium (Tio) Metal Ti (2p) Spectrum	Titanium (Tio) Metal Peak-fit of Ti (2p) Spectrum (w asymm)
Survey Spectrum of Titanium (Tio) Metal with Peaks Integrated, Assigned and Labelled
→  Periodic Table  XPS Signals for Titanium (Tio) 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 Ti (2s) 561 3.24 20.2 Ti (2p1/2) 461 2.69 21.9 Ru (3p) & In (3d) overlap Ti (2p3/2) 453.9 5.22 21.9 Na (2s) overlaps Ti (3s) 59 0.473 28.2 Ti (3p) 33 0.813 28.6 σ:  abbreviation for the term Scofield Photoionization Cross-Section which is used with IMFP and TF to generate RSFs and atom% quantitation Energy Loss Peaks Auger Peaks Energy Loss Peak:  ~18 eV above peak max Expected Bandgap for TiO22 : 3.2 eV  *Scofield Cross-Section (σ) for C (1s) = 1.0     Ti (3p) Spectrum from Titanium (Tio) Metal  Fresh exposed bulk produced by extensive Ar+ ion etching Ti (3p) Spectrum – Raw data Ti (3p) Spectrum – Peak-fit (w/o asymm)     Valence Band Spectrum from Titanium (Tio) Metal  Fresh exposed bulk produced by extensive Ar+ ion etching   Plasmon Peaks from Titanium (Tio) Metal  Fresh exposed bulk produced by extensive Ar+ ion etching Ti (2p) – Extended Range Spectrum Ti (2p) – Extended Range Spectrum – Vertically Zoomed   Ti (KLL) Auger Peaks from Titanium (Tio) Metal  Fresh exposed bulk produced by extensive Ar+ ion etching Features Observed xx xx xx →  Periodic Table
Artefacts Caused by Argon Ion Etching
Titanium Carbide(s) can form when ion etched Reactive Metal Surfaces capture Residual UHV Gases (CO, H2O, CH4 etc)	Argon Trapped in Tio can form when Argon Ions are used to removed surface contamination
Side-by-Side Comparison of Ti native oxide & Titanium Dioxide (TiO2) Peak-fits, BEs, FWHMs, and Peak Labels
Ti native oxide	TiO2  (Rutile, single crystal)
Ti (2p) from Ti native oxide Flood Gun OFF As-Measured, C (1s) at 285.2 eV	Ti (2p) from TiO2 – exposed bulk of Rutile, single crystal Flood Gun ON Charge Referenced to C (1s) at 285.0 eV
→  Periodic Table
	.
C (1s) from Ti native oxide on Titanium As-Measured, C (1s) at 285.2 eV  (Flood Gun OFF)	C (1s) from TiO2 – exposed bulk of Rutile single crystal Flood Gun ON Charge Referenced to C (1s) at 285.0 eV
→  Periodic Table
O (1s) from Ti native oxide on Titanium As-Measured, C (1s) at 285.2 eV  (Flood Gun OFF)	O (1s) from TiO2 – exposed bulk of Rutile single crystal Flood Gun ON Charge Referenced to C (1s) at 285.0 eV
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Ti (KLL) Auger Peaks from Ti metal ion etched Flood Gun ON Charge Referenced to C (1s) at 285.0 eV	Ti (KLL) Auger Peaks from TiO2 – exposed bulk of Rutile single crystal Flood Gun ON Charge Referenced to C (1s) at 285.0 eV

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Survey Spectrum of Titanium (Ti) Native Oxide
with Peaks Integrated, Assigned and Labelled

→  Periodic Table 

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Survey Spectrum of Titanium Di-oxide, TiO₂
with Peaks Integrated, Assigned and Labelled

→  Periodic Table  

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Overlays of Ti (2p) Spectra for
Titanium Ti^o metal, Ti native oxide, and TiO₂ (Rutile)
Caution: BEs from Grounded Native Oxides can be Misleading if Flood Gun is ON

Overlay of Tio metal and Ti native oxide – Ti (2p) Native Oxide C (1s) = 285.2	Overlay of Tio metal and TiO2 – Ti (2p) Pure Oxide C (1s) = 285.0 eV Chemical Shift:  4.5 eV
→  Periodic Table	Copyright ©:  The XPS Library

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Overlay of Ti (2p)
Ti^o Metal, Ti native oxide, & TiO₂ 

Features Observed

• xx
• xx
• xx

→  Periodic Table 

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Valence Band Spectra
Ti^o, TiO₂  (Rutile)

Tio Ion etched clean	TiO2 – Rutile single crystal – exposed bulk Flood gun is ON,  Charge referenced so C (1s) = 285.0 eV

Features Observed

• xx
• xx
• xx

→  Periodic Table 

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Titanium Minerals, Gemstones, and Chemical Compounds
Anatase – TiO2	Titanium Fluoride (sputter target) – TiF3	Perovskite – CaTiO3	Geikielite – MgTiO3

→  Periodic Table 

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Six (6) Chemical State Tables of Ti (2p_3/2) BEs

 

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

→  Periodic Table 

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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) 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
• There are uncertainties and error ranges in nearly all BEs 
  • Flood guns 
• 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 

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Table #1

Ti (2p_3/2) 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
Ti	22	Ti – element	453.8 eV		285.0 eV	The XPS Library
Ti	22	Ti-Si	454.1 eV		285.0 eV	The XPS Library
Ti	22	TiB2 (N*1)	454.4 eV		284.8 eV	Avg BE – NIST
Ti	22	Ti-Ni	454.5 eV		285.0 eV	The XPS Library
Ti	22	Ti-C	454.8 eV	455.0 eV	285.0 eV	The XPS Library
Ti	22	Ti-P (N*1)	454.8 eV		284.8 eV	Avg BE – NIST
Ti	22	Ti-N	454.9 eV	455.4 eV	285.0 eV	The XPS Library
Ti	22	Ti-O (N*2)	455.1 eV	455.9 eV	284.8 eV	Avg BE – NIST
Ti	22	TiS2 (N*1)	456.2 eV		284.8 eV	Avg BE – NIST
Ti	22	Ti-2O3 (N*3)	456.8 eV	456.9 eV	284.8 eV	Avg BE – NIST
Ti	22	Ti-O2	458.0 eV	458.8 eV	285.0 eV	The XPS Library
Ti	22	K2Ti4O9	458.1 eV		285.0 eV	The XPS Library
Ti	22	SrTiO23 (N*1)	458.1 eV		284.8 eV	Avg BE – NIST
Ti	22	CaTiO3	458.2 eV		285.0 eV	The XPS Library
Ti	22	SrTiO3	458.4 eV		285.0 eV	The XPS Library
Ti	22	M-TiO3 (N*5)	458.5 eV	458.9 eV	284.8 eV	Avg BE – NIST
Ti	22	CaTiO3 (N*1)	458.9 eV		284.8 eV	Avg BE – NIST
Ti	22	Ti-Fx	459.2 eV	459.6 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 (2p_3/2) BE = 932.62 eV and Au (4f_7/2) 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 

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Table #2

Ti (2p_3/2) Chemical State BEs from:  “PHI Handbook”

C (1s) BE = 284.8 eV

→  Periodic Table 

Copyright ©:  Ulvac-PHI

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Table #3

Ti (2p_3/2) Chemical State BEs from:  “Thermo-Scientific” Website

C (1s) BE = 284.8 eV

Chemical state	Binding energy (eV) Ti (2p3/2)
Ti metal	454.1
TiN	454.9
TiO2	458.5
SrTiO3	458.4

→  Periodic Table 

Copyright ©:  Thermo Scientific 

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Table #4

Ti (2p_3/2) 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

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Table #5

Ti (2p_3/2) 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 Ti 2p3/2 Ti 454.0 ±0.3 453.7 ～ 454.2 Ti 2p3/2 TiB2 454.4 ±0.2 454.2 ～ 454.5 Ti 2p3/2 TiO2 455.1 ±0.3 454.8 ～ 455.3 Ti 2p3/2 TiN 455.8 ±0.2 455.6 ～ 456.0 Ti 2p3/2 Metallocene 456.3 ±0.9 455.4 ～ 457.2 Ti 2p3/2 TiCl4 458.5 ±0.2 458.3 ～ 458.7 Ti 2p3/2 BaTiO3 (cubic,tetra.) 458.5 ±0.2 458.3 ～ 458.7 Ti 2p3/2 PbTiO3 458.6 ±0.2 458.4 ～ 458.8 Ti 2p3/2 CaTiO3 458.8 ±0.2 458.6 ～ 459.0 Ti 2p3/2 SrTiO3 458.8 ±0.2 458.6 ～ 459.0 Ti 2p3/2 TiO2 459.0 ±0.4 458.6 ～ 459.3

→  Periodic Table 

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Histograms of NIST BEs for Ti (2p_3/2) BEs

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

Histogram indicates:  453.9 eV for Tio based on 8 literature BEs	Histogram indicates:  458.7 eV for TiO2 based on 12 literature BEs

Table #6

NIST Database of Ti (2p_3/2) 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.

→  Periodic Table 

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Statistical Analysis of Binding Energies in NIST XPS Database of BEs

 

 

→  Periodic Table 

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Advanced XPS Information Section

Expert Knowledge, Spectra, Features, Guidance and Cautions
for XPS Research Studies on Titanium Materials

 

 

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Expert Knowledge Explanations

→  Periodic Table 

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Titanium Chemical Compounds

 

Peak-fits and Overlays of Chemical State Spectra

Pure Titanium:  Ti (2p) Cu (2p3/2) BE = 932.6 eV	TiO2:  Ti (2p) C (1s) BE = 285.0 eV	TiF4:  Ti (2p) C (1s) BE = 285.0 eV

Features Observed

• xx
• xx
• xx

→  Periodic Table 

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Overlay of Ti (2p) Spectra shown Above

C (1s) BE = 285.0 eV

→  Periodic Table 

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Native Oxide on Titanium (Ti^o)
Naturally Formed in lab air at 25 C^o 1 atm 

Survey Spectrum from Native Oxide on Tio Flood gun is OFF, C (1s) BE = 286.8 eV	Ti (2p) Chemical State Spectrum from Native Oxide on Tio Flood gun is OFF, C (1s) BE = 286.8 eV
	.
O (1s) Chemical State Spectrum from Native Oxide on Tio Flood gun is OFF, C (1s) BE = 286.8 eV	C (1s) Chemical State Spectrum from Native Oxide on Tio Flood gun is OFF, C (1s) BE = 286.8 eV

Features Observed

• xx
• xx
• xx

→  Periodic Table 

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Titanium Di-oxide (TiO₂)
Rutile, single crystal, cleaved to expose bulk

Survey Spectrum from TiO2 Flood gun is ON, C (1s) BE = 285.0 eV	Ti (2p) Chemical State Spectrum from TiO2 Flood gun is ON, C (1s) BE = 285.0 eV
	.
O (1s) Chemical State Spectrum from TiO2 Flood gun is ON, C (1s) BE = 285.0 eV	C (1s) Chemical State Spectrum from TiO2 Flood gun is ON, C (1s) BE = 285.0 eV
	.
Ti (3p) Chemical State Spectrum from TiO2 Flood gun is ON, C (1s) BE = 285.0 eV Freshly cleaved to expose bulk	Ti (3s) Chemical State Spectrum from TiO2 Flood gun is ON, C (1s) BE = 285.0 eV Freshly cleaved to expose bulk
	.
Valence Band Spectrum from TiO2 Flood gun is ON, C (1s) BE = 285.0 eV Freshly cleaved to expose bulk	Auger Signals from TiO2 Flood gun is ON, C (1s) BE = 285.0 eV Freshly cleaved to expose bulk

Features Observed

• xx
• xx
• xx

→  Periodic Table 

 

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Titanium Chemical Compounds

 

→  Periodic Table 

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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.

→  Periodic Table 

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Flood Gun Effect on Native Oxide of Titanium

 

Native Oxide of Titanium Sheet – Sample GROUNDED
versus
Native Oxide of Titanium Sheet – Sample FLOATING

 

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Native Oxide of Titanium Sheet – Sample Grounded

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

Ti (2p)	O (1s)	C (1s)
→  Periodic Table

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Native Oxide of Titanium Sheet – Sample Floating

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

Ti (2p)	O (1s)	C (1s)
→  Periodic Table

→  Peri

 

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AES Chemical State Spectra
from UHV Gas Captured Overnight by Freshly Ion Etched Titanium

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

Ti (LMM) Signal: Ti at front -> TiOx at rear  Ti KE = 413.9eV,    TiO2 KE = 408.5 eV	O (KLL) Signal: Ti at front -> TiOx at rear O KE = 507.3 eV
Chemical State Spectra from TiO2 using Charge Control by AES
Ti (KLL) Signal: TiO2 w charge control – JEOL Hemi-sphere (HSA) – 25 kV High Energy Resolution Mode for Chemical States	O (KLL) Signal: TiO2 w charge control – JEOL Hemi-sphere (HSA) – 25 kV High Energy Resolution Mode for Chemical States

Features Observed

• xx
• xx
• xx

→  Periodic Table 

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Titanium Alloys

XxCu	XxCu
→  Periodic Table
XxCu	XxCu

 

Copyright ©:  The XPS Library 

 

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XPS Facts, Guidance & Information

→  Periodic Table 

		Element		Titanium (Ti)
		Primary XPS peak used for Peak-fitting :		Ti (2p)
		Spin-Orbit (S-O) splitting for Primary Peak:		Spin-Orbit splitting for “p” orbital, ΔBE = 6.18 eV
		Binding Energy (BE) of Primary XPS Signal:		453.9 eV
		Scofield Cross-Section (σ) Value:		Ti (2p3/2) = 5.22     Ti (2p1/2) = 2.69
		Conductivity:		Ti resistivity =   Native Oxide suffers Differential Charing
		Range of Ti (2p) Chemical State BEs:		454-462 eV range   (Tio to TiF4)
		Signals from other elements that overlap Ti (2p) Primary Peak:		xx (xx)
		Bulk Plasmons:		~xx eV above peak max for pure
		Shake-up Peaks:		??
		Multiplet Splitting Peaks:		??
		General Information about XXX Compounds:		xx
		Cautions – Chemical Poison Warning		xx

Copyright ©:  The XPS Library 

→  Periodic Table 

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Information Useful for Peak-fitting Ti (2p)

• FWHM (eV) of Ti (2p_3/2) from Pure Ti^o :  ~0.7 eV using 50 eV Pass Energy after ion etching:
• FWHM (eV) of Ti (2p_3/2) from TiO₂ xtal:  ~1.0 eV using 50 eV Pass Energy  (before ion etching)
• Binding Energy (BE) of Primary Signal used for Measuring Chemical State Spectra:  454 eV for Ti (2p) with +/- 0.2 uncertainty
• List of XPS Peaks that can Overlap Peak-fit results for Ti (2p):  xxxx

→  Periodic Table 

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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 (3d_5/2) FWHM (eV) = ~0.95 eV for PE 50 on Thermo K-Alpha
  • Ag (3d_5/2) FWHM (eV) = ~1.00 eV for PE 80 on Kratos Nova
  • Ag (3d_5/2) 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 on Peak-fitting: ??

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 

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Contaminants Specific to Titanium

• Titanium develops a thick native oxide due to the reactive nature of clean Titanium.
• The native oxide of Ti O_x is 4-5 nm thick.
• Titanium forms a low level of carbide 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), 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 

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Data Collection Guidance

• Chemical state differentiation can be difficult
• Collect principal Ti (2p) 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 

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Data Collection Settings for Titanium (Ti)

• Conductivity:  Titanium 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:  Ti (2p) at 454 eV
• Recommended Pass Energy for Measuring Chemical State Spectrum:  40-50 eV    (Produces Ag (3d_5/2) 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:  440-480 eV
• Recommended Extended BE Range for Measuring Chemical State Spectrum:  440-540 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 

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Effects of Argon Ion Etching

• Carbides appear after ion etching Ti and 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 

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