Periodic Table
Aluminium
Quantification of Narrow Scan Spectra using Regions and Components
A peak model is developed for the
Al 2p peak using information from sputtered Al metal to design an asymmetric lineshape
for the metallic Al 2p doublet. The video shows how the LF lineshape is
adjusted to achieve a fit to the oxide and metal peaks, and the resulting
component peaks are used in the Custom Report to estimate the Al to O ratio
within the Al oxide.
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Carbon
Highly Oriented Pyrolytic Graphite (HOPG) Peak Model
Asymmetry is typically used to
explain the shape of HOPG C 1s photoemission peaks. A peak model is developed
for C 1s high resolution spectra measured from HOPG making use of the LF
lineshape to model both an asymmetric tail to the primary C 1s peak and
symmetrical lineshapes added to account for loss peaks associated with the
photoemission of graphitic C 1s signal. The LF lineshape is defined as too is
the U 2 Tougaard background approximation and together these mathematical
shapes provide a means of fitting C 1s data collected from HOPG.
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Heterogeneous Materials and C 1s Peak Models
A set of measurements from
different samples containing similar compounds is used to construct a peak
model for C 1s high resolution spectra. The video illustrate creating a peak
model based on synthetic components, energy shifts via the Calibration property
page and tools for examining the underlying structures within the C 1s spectra
from these different samples.
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Peak Model for Polymers containing Carbon Bonded to Oxygen and Hydrogen
Poly (caprolactone) (PCL) is used to illustrate how a material
homogeneous in depth and analysis-area can be analysed using a peak model
constructed using synthetic component peaks simultaneously prepared for both an
oxygen and carbon narrow scan spectra. Component constraints guide the
optimisation to a solution which is examined in the context of the known
stoichiometry for the PCL polymer.
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Poly(methyl methacrylate) (PMMA) is used to illustrate how
annotation tables showing quantification results can be defined using three
options on the Annotation dialog window. C 1s and O 1s spectra are recorded in
separate VAMAS blocks. Using these separate VAMAS blocks, a peak model for PMMA
C 1s component peaks are displayed as a components table showing only C 1s
components and also, by using the Quantification property page on the
Annotation dialog window, the relationship of the C 1s components to similar
components on the O 1s spectrum are displayed over the C 1s spectrum.
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Poly(ether ether ketone) (PEEK) is part of the Beamson and
Briggs XPS of Polymers database. The CD-ROM form of the Beamson and Briggs
database includes data in VAMAS format and the subject of the following video
is how such a database of standard spectra can be managed in CasaXPS via the
SIMS Toolbar. A comparison between a PEEK material and the standard PEEK data
within the database is performed by copying the spectra into a VAMAS file
before using vector techniques to assess the differences between the measured
spectrum and the standard spectrum for C 1s emission.
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Cerium
Ce Oxide (4+) is used to illustrate how a range of background
algorithms can be used to integrate signal above background for Ce 3d and Ce 4d
spectral forms. The display is prepared such that both Ce 3d and Ce 4d can be
clearly seen and how the choice of background algorithm alters the signal
assigned to these photoemission lines. Escape depth and angular distribution
corrected Scofield cross-sections for the Ce 3d and Ce 4d peaks are used to
compare the relative intensities for these transitions. Backgrounds
investigated include, Linear, Shirley, Tougaard, U 2 Tougaard, E Tougaard and
Curved background types.
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Chlorine
Quantification of chlorine in NaCl and KCl is examined
using a method aimed at obtain the same amount of substance when Cl 2s is used
as is obtained when Cl 2p is part of a quantification by XPS. The video shows
how a strongly Lorentzian lineshape fitted to the Cl 2s allows either Cl 2s or
Cl 2p signal adjusted using Scofield cross-sections to yield equivalent
quantification results.
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Copper
Copper Nano-particles Supported on Graphite is used to
explain how a peak model formed from lineshapes calculated from data can be
used to explain apparent inconsistencies in %atom values calculated from survey
spectra. Lineshapes derived from data are loaded from the library directory via
the Element Library dialog window and the composition of a sample is determined
from the resulting peak model involving Cu2O, CuO and Cu(OH)2.
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Chemical state for Copper may alter during an XPS experiment.
A degradation study is performed on copper initially in one oxidation state,
evidenced by secondary structure in a Cu 2p doublet, which evolves to a
different peak structure for the Cu 2p spectrum as a consequence of repeated
measurements of the sample at the same location. A sequence of spectra measured
during the experiment demonstrates a clear trend with time for this particular
material. Data treatment based on vectors identifies two forms for Cu which,
when fitted to the spectra, provides a tool for quantifying the evolution for
the sample chemistry simply due to being measured multiple times. Organisation
of VAMAS blocks within a VAMAS file is also discussed.
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Iron
Multiplet splitting is a feature of Fe 2+ and Fe 3+ oxidation states of
iron. A peak model supported by theoretical studies is used to
illustrate peak fitting techniques where the peak model is defined for one peak
of a Fe 2p doublet.
Part 1: Examining parameter constraints within a peak model
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Part 2: Optimising a peak model where the model is limited to the Fe
2p 3/2 peak of the Fe 2p doublet
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Molybdenum
Molybdenum dioxide is used to illustrate how a display state can be saved
and then restored using different VAMAS blocks as the source for the data
displayed. A display using display-tiles within display-tiles is prepared to
highlight the relationship between the O 1s and Mo 3d peaks resulting from Mo6+,
Mo5+ and Mo4+ oxidation states of molybdenum. Escape
depth corrected Scofield cross-sections coupled with a peak model for three
oxidation states of molybdenum are used to support the three-state model for Mo
3d spectra by linking Mo 3d components to O 1s intensities.
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Ruthenium
Ruthenium oxide is analysed using a peak model to identify signal from
Ru 3d and C 1s from data which contains overlapping contributions from
ruthenium and carbon. Difference spectra are calculated from spectra measured
at two sample tilt angles which exploit the inhomogeneous depth distribution of
the material in the surface region analysed by XPS to obtain variation in
carbon and ruthenium photoemission signal.
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Sodium
Sodium carbonate is potentially present in a set of samples measured
using an Ulvac PHI VersaProbe. Survey data from these samples are examined
using quantification reports gathered from both quantification regions and
synthetic component peak models. An overlap between O 1s and Na KLL Auger peaks
forces the use of a peak model and chemically distinct C 1s signal is
identified using a further peak model, both applied to the survey data as a
means of assessing whether sodium carbonate is a part of these materials. An
informed sample model approach is also applied to these survey spectra
providing further evidence for a range of carbon chemistry involving sodium and
other forms of carbon compounds.
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Titanium
Titanium oxide is used to illustrate how a U 2 Tougaard background
can be modified to provide the basis for constructing a peak model. Shirley
backgrounds and the relationship to the E Tougaard background is used to
explain how adjusting a U 2 Tougaard is performed and how the cross-section
influences the calculated Tougaard background.
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