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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
Part 2: Optimising a peak model where the model is limited to the Fe 2p 3/2 peak of the Fe 2p doublet
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.
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.
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.
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.