Mgo MgO Mg(OH)2 MgCO3 Mg(SO4)    MgAl2O4 Mg3Si4O10(OH)2  MgF2 CaMgCO3    MgWO4 Mg2Si  MgSi2 Mg3Al2(SiO4)3       

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

 

Magnesium (Mg)

 

Magnesite – MgCO3 Magnesium – Mgo Forsterite – Mg2SiO4

 

  Page Index
  • Expert Knowledge Explanations

 

Magnesium (Mgo) Metal
Peak-fits, BEs, FWHMs, and Peak Labels

 

Magnesium (Mgo) Metal
Mg (2p) Spectrum – Very High Energy Resolution – PE = 5 eV
spin-orbit splitting produces peak-shoulder near peak max
ion etched clean,  Splitting ΔBE = ~0.3 eV		 Magnesium (Mgo) Metal
Peak-fit of Mg (2p) Spectrum using PE = 5 eV
not using peak asymmetry
using 2p3/2 to 2p1/2 peak area ratio to constrain peak-fit

→  Periodic Table – HomePage 
Magnesium (Mgo) Metal
Mg (2p) Spectrum – raw spectrum
window includes first plasmon peak at ~60 eV		 Magnesium (Mgo) Metal
Peak-fit of Mg (2p) Spectrum (w/o asymm)
not using peak area ratio for peak-fit

 
Magnesium (Mgo) Metal
Mg (2s) Spectrum – raw spectrum
 Magnesium (Mgo) Metal
Peak-fit of Mg (2s) Spectrum (w/o asymm)

→  Periodic Table – HomePage 
Magnesium (Mgo) Metal
Mg (1s) Spectrum
window includes three plasmon peaks
 Magnesium (Mgo) Metal
Peak-fit of Mg (1s) Spectrum (w/o asymm)
not using peak asymmetry



Survey Spectrum of Magnesium (Mgo) Metal
with Peaks Integrated, Assigned and Labelled

→  Periodic Table 

 

XPS Signals for Magnesium, Mgo 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
  Mg (1s) 1303.13 3.8 8.2
Mn (3s), Pd (4s), Au (4f) & Fe (3s) overlap Mg (2s) 88.62  0.3335 37.4
Li (1s) overlaps Mg (2p) 49.65  0.575 38.2

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

Auger Peaks

Intrinsic Plasmon Peak:  ~11 eV above peak max
Expected Bandgap for MgO: 7.8 eV 

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

 


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

 

 

Plasmon Peaks from Pure Magnesium, Mgo
 Fresh exposed bulk produced by extensive Ar+ ion etching

Mg (2p) – Extended Range Spectrum Mg (2p) – Extended Range Spectrum – Vertically Zoomed
   
Mg (KLL) Auger Peaks from Pure Mgo
 Fresh exposed bulk produced by extensive Ar+ ion etching

 

Expanded View of Main Mgo Auger Peak at 301 eV
commonly overlaps C (1s) loss

 

 

Artefacts Caused by Argon Ion Etching

C (1s) from Magnesium Carbide(s) Argon Trapped in Mg
   
   

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Side-by-Side Comparison of
Fresh Mg Native Oxide & Magnesium Oxide (MgO)
Peak-fits, BEs, FWHMs, and Peak Labels
Mg Native Oxide Pure MgO <100> single crystal
Mg (2p) from FRESH Mg Native Oxide
on Magnesium metal
Flood Gun OFF, As-Measured, C (1s) at 286.8 eV 		 Mg (2p) from MgO crystal
Flood Gun ON – fresh exposed bulk
Charge Referenced to C (1s) at 285.0 eV
   
C (1s) from FRESH Mg Native Oxide (w carbide)
on Magnesium metal
As-Measured, C (1s) at 286.8 eV (Flood Gun OFF)
C (1s) shifts by 1.8 eV for Native Mg Oxide but Mg (2p) BE does not!

C (1s) from MgO crystal
Flood Gun ON – fresh exposed bulk
Charge Referenced to C (1s) at 285.0 eV
Mg Auger Peaks Overlap C (1s)
.
O (1s) from FRESH Mg Native Oxide
on Magnesium metal
As-Measured, C (1s) at 286.8 eV (Flood Gun OFF)

O (1s) from MgO crystal
Flood Gun ON – fresh exposed bulk
Charge Referenced to C (1s) at 285.0 eV
.
Mg (KLL) Auger Peaks from FRESH Mg Native Oxide
on Magnesium metal
As-Measured, C (1s) at 286.8 eV (Flood Gun OFF)

Mg (KLL) Auger Peaks from MgO crystal
Flood Gun ON – fresh exposed bulk
Charge Referenced to C (1s) at 285.0 eV

 

Survey Spectrum of Magnesium (Mg) Native Oxide
with Peaks Integrated, Assigned and Labelled

 

 

Survey Spectrum of Magnesium Oxide, MgO
with Peaks Integrated, Assigned and Labelled

 

Copyright ©:  The XPS Library 


Overlays of Mg (2p) Spectra for
Mgo metal, Mg Native Oxide, and Pure MgO Crystal

Caution: BEs from Grounded Native Oxides can be Misleading if Flood Gun is ON

 Overlay of Mgo metal and Mg Native Oxide – Mg (2p) BE
Mg Native Oxide C (1s) = 286.8 eV  (Flood gun OFF)
Chemical Shift: 1.5 eV between Mg and Mg-oxide peak max
  Overlay of Mgo metal and Pure MgO xtal – Mg (2p) BE
Pure MgO C (1s) = 285.0 eV
Chemical Shift: 2.3 eV
  Copyright ©:  The XPS Library 

 

Overlay of Mg (2p)
Mgo metal, Mg Native Oxide, & Pure MgO (crystal)

Chemical Shift between Mgo and MgO (native): 1.5 eV
Chemical Shift between Mgo and MgO : 2.3 eV

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Valence Band Spectra
Mgo, MgO (single crystal)

Mgo
Ion etched clean		 MgO xtal – exposed bulk
Flood gun is ON,  Charge referenced so C (1s) = 285.0 eV
Freshly cleaved to expose bulk

 

Overlay of Valence Band Spectra for
Mgo metal and MgO

 

Mg (2p) and Mg (2s) Peak-shape Comparison 
 Overlay Study
Mg (2p) Mg (2s)

Overlay Study of
Mg (2p) and Mg (2s)

 

Overlay Study of
Mg (1s) and Mg (2s)

 

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Magnesium Minerals, Gemstones, and Chemical Compounds

 
Periclase – MgO Sellaite – MgF2 Dolomite – MgCa(CO3)2 Diopside – MgCaSi2O6

 

 

 

Six (6) Chemical State Tables of Mg (2p) 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

Mg (2p) 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
Mg 12 Mg(OH)2 (N*1) 49.5 eV   284.8 Avg BE – NIST
Mg 12 Mg – element 49.7 eV   285.0 The XPS Library
Mg 12 Mg-O (N*3) 50.3 eV 51.1 eV 284.8 Avg BE – NIST
Mg 12 Mg-Si 50.4 eV   285.0 The XPS Library
Mg 12 MgF2 (N*2) 50.9 eV 51.0 eV 284.8 Avg BE – NIST
Mg 12 Mg-(OH)2 51.3 eV   285.0 The XPS Library
Mg 12 MgO native 51.4 eV   286.8 The XPS Library
Mg 12 Mg-O 51.6 eV   285.0 The XPS Library
Mg 12 MgF2 52.2 eV   285.0 The XPS Library
Mg 12 Mg-CO3 52.0 eV   285.0 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

Mg (2p) Chemical State BEs from:  “PHI Handbook”

C (1s) BE = 284.8 eV

→  Periodic Table 

Copyright ©:  Ulvac-PHI

Table #3

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

C (1s) BE = 284.8 eV

Chemical state Binding energy
Mg (1s)
Mg 1303 eV
Mg native oxide 1304 eV
MgCO3 1305 eV

→  Periodic Table 

Copyright ©:  Thermo Scientific 

Table #4

Mg (2p) 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

Mg (2p) 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
Mg 2p Mg(OH)2 49.5 ±0.3 49.2 ～ 49.8
Mg 2p Mg 49.7 ±0.2 49.5 ～ 49.8
Mg 2p Mg2Cu 49.9 ±0.3 49.6 ～ 50.1
Mg 2p MgAl2O4 50.4 ±0.3 50.1 ～ 50.6
Mg 2p Mg3Bi2 50.7 ±0.2 50.5 ～ 50.9
Mg 2p MgF2 51.0 ±0.2 50.8 ～ 51.2

 

→  Periodic Table 

 

Histograms of NIST BEs for Mg (2p) BEs

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

Histogram indicates:  49.6 eV for Mgo based on 11 literature BEs Histogram indicates:  50.7 eV for MgO based on 3 literature BEs

Table #6


NIST Database of Mg (2p) 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
Mg 2p Mg 49.30  Click
Mg 2p Mg 49.40  Click
Mg 2p Mg 49.40  Click
Mg 2p Mg(OH)2 49.50  Click
Mg 2p Mg 49.60  Click
Mg 2p Mg 49.60  Click
Mg 2p Mg 49.60  Click
Mg 2p MgAl2O4 49.60  Click
Mg 2p Mg 49.70  Click
Mg 2p Mg/Ru 49.70  Click
Mg 2p Mg/Mo 49.74  Click
Mg 2p Mg/Mo 49.74  Click
Mg 2p Mg 49.77  Click
Mg 2p Mg 49.80  Click
Mg 2p K0.7(NaCa)0.3(Mg2.84Fe0.02)Al1.2Si2.8O10(OH1.5F0.50) 49.80  Click
Mg 2p K0.7(NaCa)0.3(Mg2.84Fe0.02)Al1.2Si2.8O10(OH1.5F0.50) 49.80  Click
Mg 2p Mg/Mo 49.84  Click
Mg 2p Mg/Mo 49.84  Click
Mg 2p Mg/Mo 49.89  Click
Mg 2p Mg/Mo 49.89  Click
Mg 2p Mg 49.90  Click
Mg 2p CO/MgO/Mo 49.90  Click
Mg 2p Mg/Mo 49.90  Click
Mg 2p Mg/Mo 49.90  Click
Mg 2p O2/Mg/Mo 49.90  Click
Mg 2p O2/Mg/Mo 49.90  Click
Mg 2p Ca2[Mg5][Si8O22]OH2 49.90  Click
Mg 2p Ca2[Mg5][Si8O22](OH)2 49.90  Click
Mg 2p Mg 49.95  Click
Mg 2p Mg/Mo 50.00  Click
Mg 2p O2/Mg/Mo 50.00  Click
Mg 2p O2/Mg/Mo 50.00  Click
Mg 2p MgAl2.2O4.9 50.15  Click
Mg 2p MgAl2O5 50.15  Click
Mg 2p MgV2O6 50.20  Click
Mg 2p K0.9(Mg1.56Fe1.14Ti0.11)Al0.96Si3.0O10(OH1.44F0.56) 50.20  Click
Mg 2p K0.9(Mg1.56Fe1.14Ti0.11)Al0.96Si3.0O10(OH1.44F0.56) 50.20  Click
Mg 2p (K,Ca)2[Mg4.3Fe0.7][Si7.2Al0.8O22](OH)2 50.20  Click
Mg 2p MgO 50.25  Click
Mg 2p MgH2 50.30  Click
Mg 2p MgO/Mo 50.30  Click
Mg 2p O2/Mg/Mo 50.30  Click
Mg 2p Mg(CH3COO)2 50.35  Click
Mg 2p MgAl2O4 50.40  Click
Mg 2p MgAl2.3O4.8/SiO2 50.40  Click
Mg 2p MgAl2.2O4.7/SiO2 50.40  Click
Mg 2p MgAl2.7O5.3/SiO2 50.40  Click
Mg 2p O2/Mg/Mo 50.40  Click
Mg 2p (Na,Ca)0.5Fe1.0[Mg1.2Fe1.5Al2.3][Si6.8Al1.2O22](OH)2 50.45  Click
Mg 2p Mg3H2(SiO3)4 50.46  Click
Mg 2p (MgO)2(Al2O3)2(SiO2)5 50.50  Click
Mg 2p O2/Mg/Mo 50.50  Click
Mg 2p MgAl2.2O4.75 50.50  Click
Mg 2p Mg0.059Al0.126P0.158O0.635 50.50  Click
Mg 2p O2/Mg/Mo 50.60  Click
Mg 2p O2/Mg/Mo 50.60  Click
Mg 2p O2/Mg/Mo 50.70  Click
Mg 2p MgAl2.2O4.75 50.70  Click
Mg 2p Mg2[Mg5][Si8O22]OH2 50.70  Click
Mg 2p MgO 50.80  Click
Mg 2p O2/Mg/Mo 50.80  Click
Mg 2p MgF2 50.90  Click
Mg 2p (Ca1.6Mg0.4)[Mg2.0Fe1.9Al1.0][Si7.2Al0.8O22](OH,Cl) 50.90  Click
Mg 2p MgF2 50.95  Click
Mg 2p MgO 51.00  Click
Mg 2p O2/Mg/Ru 51.00  Click
Mg 2p MgO/Mg 51.10  Click
Mg 2p O2/Mg/Mo 51.10  Click
Mg 2p O2/Mg/Mo 51.10  Click
Mg 2p O2/Mg/Mo 51.10  Click
Mg 2p O2/Mg/Mo 51.10  Click
Mg 2p Mg2[Mg5][Si8O22]OH2 51.15  Click
Mg 2p O2/Mg/Mo 51.20  Click
Mg 2p O2/Mg/Mo 51.20  Click
Mg 2p (MgO)2(Al2O3)2(SiO2)5 51.40  Click
Mg 2p MgCl2/Au 52.90  Click
 
 
 
 
 
 
 
 
 

→  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 Magnesium Materials

 

 

Expert Knowledge Explanations

 

 

Magnesium Chemical Compounds


Peak-fits and Overlays of Chemical State Spectra

 

Pure Magnesium:  Mg (2p)
Cu (2p3/2) BE = 932.6 eV		 MgO:  Mg (2p)
Charge Referenced to C (1s) BE = 285.0 eV		 MgF2:  Mg (2p)
Charge Referenced to C (1s) BE = 285.0 eV

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Overlay of Mg (2p) Spectra – shown Above

Charge Referenced to C (1s) BE = 285.0 eV

Chemical Shift between Mg and MgO:  1.9 eV
 Chemical Shift between Mg and MgF2:  2.6 eV

→  Periodic Table 

 

FRESH Native Oxide on Magnesium , Mgo
Naturally Formed in lab air at 25 Co 1 atm after freshly scraping clean (age ~10 min)

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

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

 

 

Magnesium Oxide (MgO)
Single Crystal <100> cleaved to expose bulk

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

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 


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 

 

 

Flood Gun Effect on Native Oxide of Magnesium

 

Native Oxide of Magnesium Ribbon – Sample GROUNDED
versus
Native Oxide of Magnesium Ribbon – Sample FLOATING

 

 

Native Oxide of Magnesium Disk – Sample Grounded

Electron Flood Gun:  0 Voltage (FG OFF), Min Voltage versus Max Voltage
Mg (2p) O (1s) C (1s)
Differential Shift of MgO Peak is due to
Differential Charging		 Differential Shift of O (1s) Peak is due to
Differential Charging		 Differential Shift of Adventitious Carbon
is a Slightly Larger

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table

Native Oxide of Magnesium Disk – Sample Floating

Electron Flood Gun:  0 Voltage (FG OFF), Min Voltage versus Max Voltage
Mg (2p) O (1s) C (1s)
All Peaks Shift Linearly
NO Differential Charging		 All Peaks Shift Linearly
NO Differential Charging		 All Peaks Shift Linearly
NO Differential Charging

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

XPS Study of UHV Gas Capture by Freshly Ion Etched Magnesium
 
Reveals Chemical Shifts and Chemical States that Develop from Ion Etched Pure Mgo

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.
 
 
Mg (2p) Signal
  O (1s) Signal C (1s) Signal
     
 
 
Copyright ©:  The XPS Library

 

AES Study of UHV Gas Capture by Freshly Ion Etched Magnesium

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

Mg (KLL) Signal:
MgO at front -> Mg at rear (normal display)
Mg KE = 1118.1 eV,    MgO KE = 1176.7 eV		 O (KLL) Signal:
MgO at rear -> Mg at front (display reversed)
O KE = 504.8 eV
   

 
Auger Chemical State Spectra from MgO Single Crystal
using Charge Control 
 
Mg (KLL) Signal:
MgO w charge control – CHA based Auger – 25 kV
High Energy Resolution Mode for Chemical States		 O (KLL) Signal:
MgO w charge control – CHA based Auger  – 25 kV
High Energy Resolution Mode for Chemical States


Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Slow Depth Profile to reveal Chemical States
of Mg Native Oxide by AES

Native Mg Oxide on Mg ribbon was slowly ion etched using High Energy Resolution conditions to measure Chemical States by Auger

Mg (KLL) O (KLL)
   

 

 

 

Magnesium Alloys

   
XxCu XxCu
→  Periodic Table   
XxCu XxCu

 

Copyright ©:  The XPS Library 

 

 

XPS Facts, Guidance & Information

→  Periodic Table 

    Element   Magnesium (Mg)
  
    Primary XPS peak used for Peak-fitting :   Mg (2p)  
    Spin-Orbit (S-O) splitting for Primary Peak:   Spin-Orbit splitting for “p” orbital, ΔBE = 0.3 eV
  
    Binding Energy (BE) of Primary XPS Signal:   49.65 eV
  
    Scofield Cross-Section (σ) Value:   Mg (2p) =0.1947
  
    Conductivity:   Mg resistivity = 43.9 nΩ⋅m (at 20 °C)
MgO resistivity = ~1E8 Ω⋅cm
 form is very conductive
Native Oxide suffers Differential Charing		  
    Range of Mg (2p) Chemical State BEs:   49 – 52 eV range   (Mgo to MgF2)  
    Signals from other elements that overlap
Mg (2p) Primary Peak:		   Fe (3p)  
    Bulk Plasmons:   ~11 eV above peak max for pure  
    Shake-up Peaks:   ??  
    Multiplet Splitting Peaks:   not possible  

 

 

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

xx 

  

Copyright ©:  The XPS Library 

 

Information Useful for Peak-fitting Mg (2p)

  • FWHM (eV) of Mg (2p) for Pure Mgo :  ~0.67 eV using 50 eV Pass Energy after ion etching:
  • FWHM (eV) of Mg (2p) for MgO xtal:  ~1.54 eV using 50 eV Pass Energy  (before ion etching)
  • Binding Energy (BE) of Primary Signal used for Measuring Chemical State Spectra:  49.6 eV for Mg (1s) with +/- 0.1 uncertainty
  • List of XPS Peaks that can Overlap Peak-fit results for Mg (2p):  Fe (3p)

→  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.

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 Magnesium

  • Magnesium develops a thick native oxide due to the reactive nature of clean Magnesium .
  • The native oxide of MgOx is 6-7 nm thick.
  • Magnesium thin films often have a low level of iron (Fe) in the bulk as a contaminant or to strengthen the thin film
  • Magnesium 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 

 

Data Collection Guidance

  • Chemical state differentiation can be difficult
  • Collect principal Mg (2p) peak as well as Mg (1s).
  • 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 Magnesium (Mg)

  • Conductivity:  Magnesium 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:  Mg (1s) at 49.6 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:  40 – 60 eV
  • Recommended Extended BE Range for Measuring Chemical State Spectrum:  40 – 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 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 Mg 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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Chemical State Spectra from Literature
 
Spectra from Thermo Scientific
 
 

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