| Hgo | HgO | HgS | HgSO4 | HgTe | HgCdTe | HgF2 | Basic |
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
Mercury (Hg)
Hydrargyrum
| Montroydite – HgO | Natural Mercury – Hgo | Cinnabar – HgS |
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- Expert Knowledge & Explanations
Peak-fits, BEs, FWHMs, and Peak Labels
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| Mercury (Hgo) Metal Hg (4f) Spectrum – raw spectrum ion etched clean |
Mercury (Hgo) Metal Peak-fit of Hg (4f) Spectrum w/o asymm |
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| → Periodic Table – HomePage | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mercury (Hgo) Metal Hg (4f) Spectrum – extended range |
Mercury (Hgo) Metal Peak-fit of Hg (4f) Spectrum (w asymm) |
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Survey Spectrum of Mercury (Hgo) Metal |
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| → Periodic Table
XPS Signals for Mercury (Hgo) Metal Spin-Orbit Term, BE (eV) Value, and Scofield σ for Aluminum Kα X-rays (1486 eV, 8.33 Ang)
σ: abbreviation for the term Scofield Photoionization Cross-Section which is used with IMFP and TF to generate RSFs and atom% quantitation Plasmon Peaks Expected Bandgap for HgO: 2.6 – 3.0 eV *Scofield Cross-Section (σ) for C (1s) = 1.0
Valence Band Spectrum from Hgo Metal
Plasmon Peaks from Hgo Metal
Features Observed
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Artefacts Caused by Argon Ion Etching |
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C (1s) from Mercury Carbide(s) can form when ion etched Reactive Metal Surfaces capture |
Argon Trapped in Hgo can form when Argon Ions are used |
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Hgo metal & Mercuric Oxide (HgO) |
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| Hgo bead in UHV | HgO | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Hg (4f) from Hgo liquid bead in UHV Flood Gun OFF As-Measured, C (1s) at 285.2 eV |
Hg (4f) from HgO – pressed pellet Flood Gun ON Charge Referenced to C (1s) at 285.0 eV |
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| Hgo bead in UHV | HgO | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| C (1s) from Hgo bead in UHV As-Measured, C (1s) at 285.2 eV Flood Gun OFF |
C (1s) from HgO – pressed pellet |
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| Hgo bead in UHV | HgO | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| O (1s) from Hgo bead in UHV As-Measured, C (1s) at 285.2eV Flood Gun OFF |
O (1s) from HgO – pressed pellet |
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Survey Spectrum of Mercury, Hgo metal
with Peaks Integrated, Assigned and Labelled
Survey Spectrum of Mercuric Oxide, HgO
with Peaks Integrated, Assigned and Labelled
Overlays of Hg (4f) Spectra for
Hgo metal, HgO, and Mercuric Sulfide, HgS
Caution: BEs from Grounded Native Oxides can be Misleading if Flood Gun is ON
| Overlay of Hgo metal and HgO – Hg (4f) C (1s) = 285.0 eV (Flood gun ON) Chemical Shift: 0.89 eV |
Overlay of Hgo metal and HgS – Hg (4f) Pure Oxide C (1s) = 285.0 eV Chemical Shift: 1.1 eV |
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| → Periodic Table | Copyright ©: The XPS Library |
Overlay of Hg (4f)
Hgo Metal, HgO, & HgS
Features Observed
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| Hgo Ion etched clean |
HgO – pressed pellet Flood gun is ON, Charge referenced so C (1s) = 285.0 eV |
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Overlay of Valence Band Spectra for Hgo metal and HgO |
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Overlay of Valence Band Spectra
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Features Observed
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| Mercury Minerals, Gemstones, and Chemical Compounds
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| Calomel – HgCl2 | Coccinite – HgI2 | Imiterite – Ag2HgS2 | Tiemannite – HgSe |
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Six (6) Chemical State Tables of Hg (4f7/2) 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 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.
Table #1
Hg (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 |
| Hg | 80 | HgTe (N*1) | 99.9 eV | 284.8 eV | Avg BE – NIST | |
| Hg | 80 | Hg – element | 99.8 eV | 285.0 eV | The XPS Library | |
| Hg | 80 | Hg-F2 (N*1) | 101.2 eV | 284.8 eV | Avg BE – NIST | |
| Hg | 80 | Hg2(NO3)2 (N*2) | 101.1 eV | 101.2 eV | 284.8 eV | Avg BE – NIST |
| Hg | 80 | Hg-S | 100.9 eV | 285.0 eV | The XPS Library | |
| Hg | 80 | Hg-O | 100.9 eV | 285.0 eV | The XPS Library | |
| Hg | 80 | HgS (N*1) | 100.8 eV | 284.8 eV | Avg BE – NIST | |
| Hg | 80 | HgO (N*3) | 100.8 eV | 284.8 eV | Avg BE – NIST | |
| Hg | 80 | Hg-I2 (N*1) | 100.7 eV | 284.8 eV | Avg BE – NIST | |
| Hg | 80 | HgCdTe | 100.6 eV | 285.0 eV | The XPS Library | |
| Hg | 80 | HgTe | 100.5 eV | 285.0 eV | The XPS Library | |
| Hg | 80 | HgCdTe (N*1) | 100.2 eV | 284.8 eV | Avg BE – NIST | |
| Hg | 80 | Hg-CO3 | 285.0 eV | The XPS Library | ||
| Hg | 80 | Hg-(OH)2 | 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)
Table #2
Hg (4f7/2) Chemical State BEs from: “PHI Handbook”
C (1s) BE = 284.8 eV
Copyright ©: Ulvac-PHI
Table #3
Hg (4f7/2) Chemical State BEs from: “Thermo-Scientific” Website
C (1s) BE = 284.8 eV
| Chemical state | Binding energy (eV), Hg (4f7/2) |
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| As received Cinnabar (HgS) | 100.3 eV |
Copyright ©: Thermo Scientific
Table #4
Hg (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
Copyright ©: Mark Beisinger
Table #5
Hg (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
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Histograms of NIST BEs for Hg (4f7/2) BEs
Important Note: NIST Database defines Adventitious Hydrocarbon C (1s) BE = 284.8 eV for all insulators.
| Histogram indicates: 99.8 eV for Hgo based on 4 literature BEs | Histogram indicates: 100.8 eV for HgO based on 3 literature BEs |
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Table #6
NIST Database of Hg (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 |
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| Hg | 4f7/2 | Hg | 99.70 | Click |
| Hg | 4f7/2 | Hg | 99.80 | Click |
| Hg | 4f7/2 | Hg | 99.82 | Click |
| Hg | 4f7/2 | Hg | 99.90 | Click |
| Hg | 4f7/2 | Hg | 99.90 | Click |
| Hg | 4f7/2 | HgTe | 99.91 | Click |
| Hg | 4f7/2 | HgS | 100.00 | Click |
| Hg | 4f7/2 | [P(C6H5)3Pt(AuP(C6H5)3)6(HgNO3)]NO3 | 100.10 | Click |
| Hg | 4f7/2 | Cd0.2Hg0.8Te | 100.20 | Click |
| Hg | 4f7/2 | [P(C6H5)3Pt(AuP(C6H5)3)5(HgNO3)2]NO3 | 100.30 | Click |
| Hg | 4f7/2 | [(Pt2(P(C6H5)3)4S2)2Hg][PF6]2 | 100.40 | Click |
| Hg | 4f7/2 | K2[Hg(SCN)4] | 100.50 | Click |
| Hg | 4f7/2 | HgI2((CH3)2NC6H4NO) | 100.50 | Click |
| Hg | 4f7/2 | Hg/CO/W | 100.50 | Click |
| Hg | 4f7/2 | Hg/H2/W | 100.50 | Click |
| Hg | 4f7/2 | Hg/O2/W | 100.50 | Click |
| Hg | 4f7/2 | Hg/W | 100.50 | Click |
| Hg | 4f7/2 | Hg0.7Ba2.4CaCu2O8 | 100.60 | Click |
| Hg | 4f7/2 | Hg2Br2 | 100.70 | Click |
| Hg | 4f7/2 | HgI2 | 100.70 | Click |
| Hg | 4f7/2 | HgO | 100.77 | Click |
| Hg | 4f7/2 | Hg2(C2H3O2)2 | 100.80 | Click |
| Hg | 4f7/2 | Hg2Cl2 | 100.80 | Click |
| Hg | 4f7/2 | HgO | 100.80 | Click |
| Hg | 4f7/2 | HgO | 100.80 | Click |
| Hg | 4f7/2 | HgS | 100.80 | Click |
| Hg | 4f7/2 | [(Pt(P(C6H5)3)2S)2Hg(C6H5)2PCH2CH2P(C6H5)2)][PF6]2 | 100.80 | Click |
| Hg | 4f7/2 | Hg2I2 | 100.90 | Click |
| Hg | 4f7/2 | HgBr2 | 101.00 | Click |
| Hg | 4f7/2 | Hg2SO4 | 101.00 | Click |
| Hg | 4f7/2 | HgS | 101.00 | Click |
| Hg | 4f7/2 | Hg2C2O4 | 101.10 | Click |
| Hg | 4f7/2 | Hg2(NO2)2 | 101.10 | Click |
| Hg | 4f7/2 | Hg3PO4 | 101.10 | Click |
| Hg | 4f7/2 | HgF2 | 101.20 | Click |
| Hg | 4f7/2 | Hg2(NO3)2 | 101.20 | Click |
| Hg | 4f7/2 | [Hg(C6H5C(O)CHC(S)C6H5)2] | 101.25 | Click |
| Hg | 4f7/2 | [Hg(H2NC(O)NHC(O)NH2)2]Cl2 | 101.30 | Click |
| Hg | 4f7/2 | [Hg(C2H3O2)(C6H4)N(C2H5)2] | 101.30 | Click |
| Hg | 4f7/2 | [Hg(SCN)4(P(C6H5)4)2] | 101.40 | Click |
| Hg | 4f7/2 | HgCl2 | 101.40 | Click |
| Hg | 4f7/2 | (CH3(CH2)20C(O)O)2Hg/CaF2 | 101.50 | Click |
Statistical Analysis of Binding Energies in NIST XPS Database of BEs
Advanced XPS Information Section
Expert Knowledge, Spectra, Features, Guidance and Cautions
for XPS Research Studies on Mercury Materials
Expert Knowledge Examples & Explanations
Mercury Chemical Compounds
Peak-fits and Overlays of Chemical State Spectra
| Pure Mercury, Hgo: Hg (4f) Cu (2p3/2) BE = 932.6 eV |
HgO: Hg (4f) C (1s) BE = 285.0 eV |
HgF2: Hg (4f) C (1s) BE = 285.0 eV |
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Features Observed
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Overlay of Hg (4f) Spectra shown Above
C (1s) BE = 285.0 eV
Chemical Shift between Hg and HgO: 0.86 eV
Chemical Shift between Hg and HgF2: 1.2 eV
Mercury Oxide (HgO)
pressed pellet
| Survey Spectrum from HgO Flood gun is ON, C (1s) BE = 285.0 eV |
Hg (4f) Chemical State Spectrum from HgO Flood gun is ON, C (1s) BE = 285.0 eV |
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| O (1s) Chemical State Spectrum from HgO Flood gun is ON, C (1s) BE = 285.0 eV |
C (1s) Chemical State Spectrum from HgO Flood gun is ON, C (1s) BE = 285.0 eV |
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| Valence Band Spectrum from HgO Flood gun is ON, C (1s) BE = 285.0 eV |
Auger Signals from HgO Flood gun is ON, C (1s) BE = 285.0 eV |
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Shake-up Features for HgO
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Multiplet Splitting Features for Mercury Compounds
| Hg metal – NO Splitting for Hg (4s) | HgO – Splitting Peaks for Hg (4s) |
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Features Observed
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Mercury Chemical Compounds
Mercuric Fluoride, HgF2
| Survey Spectrum | Hg (4f) Spectrum |
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| C (1s) Spectrum | F (1s) Spectrum |
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| Valence Band Spectrum | Degradation Estimate |
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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 Mercury – HgO
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.
Mercury Alloys
| XxCu | XxCu |
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| → Periodic Table | |
| XxCu | XxCu |
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Copyright ©: The XPS Library
XPS Facts, Guidance & Information
| Element | Mercury (Hg) |
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| Primary XPS peak used for Peak-fitting: | Hg (4f7/2) | ||||
| Spin-Orbit (S-O) splitting for Primary Peak: | Spin-Orbit splitting for “f” orbital, ΔBE = 4.0 eV |
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| Binding Energy (BE) of Primary XPS Signal: | 99.8 eV |
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| Scofield Cross-Section (σ) Value: | Hg (4f7/2) = 10.57 Hg (4f5/2) = 8.32 |
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| Conductivity: | Hg resistivity = Native Oxide suffers Differential Charing |
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| Range of Hg (4f7/2) Chemical State BEs: | 99 – 102 eV range (Hgo to HgF2) | ||||
| Signals from other elements that overlap Hg (4f7/2) Primary Peak: |
Si (2p) | ||||
| Bulk Plasmons: | ~xx eV above peak max for pure | ||||
| Shake-up Peaks: | xx | ||||
| Multiplet Splitting Peaks: | xx | ||||
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General Information about XXX Compounds: |
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| Cautions – Chemical Poison Warning |
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Copyright ©: The XPS Library
Information Useful for Peak-fitting Hg (4f7/2)
- FWHM (eV) of Hg (4f7/2) for Pure Hgo : ~0.65 eV using 25 eV Pass Energy after ion etching
- FWHM (eV) of Hg (4f7/2) for HgO: ~1.1 eV using 50 eV Pass Energy (before ion etching)
- Binding Energy (BE) of Primary Signal used for Measuring Chemical State Spectra: 99.8 eV for Hg (4f7/2) with +/- 0.2 uncertainty
- List of XPS Peaks that can Overlap Peak-fit results for Hg (4f7/2): Si (2p)
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.
- 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 a very few compounds are negative due to unusual electron polarization.
Contaminants Specific to Mercury
- Mercury develops a thick native oxide due to the reactive nature of clean Mercury.
- The native oxide of HgOx is 1-2 nm thick.
- Mercury thin films can have a low level of iron (Fe) in the bulk as a contaminant or due to sputter coater shields
- Mercury 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
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 Hg (4f) 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.
Data Collection Settings for Mercury (Hg)
- Conductivity: Mercury 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: Hg (4f7/2) at 99.8 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: 90 – 110 eV
- Recommended Extended BE Range for Measuring Chemical State Spectrum: 80 – 180 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
Effects of Argon Ion Etching
- Carbides appear after ion etching Hg 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
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