Specific Process Knowledge/Characterization/XRD/SLSII analysis

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Unless otherwise stated, this page is written by DTU Nanolab staff

XRD data analysis in SmartLab Studio II

SmartLab Studio II is an integrated software package, which from 2020 onwards has combined the functionality previously available to Nanolab users in the programs SmartLab Guidance, GlobalFit, PDXL, 3D explorer, and DataMapper. When SmartLab Studio II is installed on your personal computer as described here, you will have access to all the data analysis tools, but not the machine control.

Licenses for the software are floating network licenses, and hence you must close the software when you are not using it. User management and data transfer can be done by connecting to the SQL server (the database) as described in the link above.

Plugins available for data treatment are listed below. Each plugin is named by the data treatment type.

Help functions included in the program usually give a good overview of the options available when setting up fitting. In many cases they also explain a bit of the theory applied. You can access the relevant help sections by clicking on the small question mark in the pane you want to know more about. The exception is that in the software in the cleanroom the question marks do not work properly (the computer is running a very early version of SLSII and it seems that the help function was not yet properly integrated). The help function should work on the installation on your computer, but if it doesn't, you can find the full help documents on the Cleanroom Drive and some are also available in LabManager, just follow the links below.

XRR

X-Ray Reflectivity, like ellipsometry, requires some prior knowledge of the sample for proper fitting of the data. In SLSII you create a layer structure with initial parameters. Then the software will generate and fit a model to obtain the thickness, roughness, and density of your layers.

How to analyze XRR data:

1. Load data
2. Configure sample model:
   1. Set substrate material and initial values.
   2. Add layers. Consider adding interface layers like native oxides.
   3. Set layer materials and initial values.
   4. Define Graded Layers if any.
   5. Define Super Lattices if any.
   6. Link layers (formula is of the type th[1] for linking thickness to layer L1).
3. Oscillation analysis (optional):
   1. Run Analysis.
   2. Look over the list of Residual oscillation components.
   3. Check if the number of layers and the thickness are as expected.
   4. If acceptable, Optimize and Apply Sample.
4. Set simulation parameters.
   1. Check the Horizontal axis angles, to exclude the noise tail from the fit.
   2. Consider to auto transform the Horizontal and Vertical axes.
5. Set fit algorithm and run fit
   1. Select the Fit method: Genetic Algorithm is for global optimization, while the two others are local optimizations.
   2. Change fit method parameters and settings as needed. E.g., in the genetic algorithm it's often a good idea to use 10 times more individuals than the default (500 instead of 0) and set the Chi2 value a factor of 10 lower to E-5.
   3. (Optional) Set an instrumental function in the tab below the fit parameters window.

It is not easy to evaluate the accuracy of the fit. However, a Rigaku specialist told us that the value of the thickness should be accurate within 1 nm, as it is mostly based on the oscillation frequency, which is relatively simple to fit. The accuracy of the thickness determination probably decreases, however, if there are many layers or graded layers, although those can be included in the fit.

For more information on how to use the XRR plugin, read the manual by clicking on the ? in the software or find it here in LabManager - requires login.

HRXRD

The HRXRD package is used with rocking curves and reciprocal space mapping data to derive information about crystallinity, strain, composition, and thickness. These measurements are usually made on epitaxial layers and single-crystal substrates. Like the XRR plugin, the flow is to load data, generate a model of the layers, simulate initial parameters, and finally fit the model to the data.

Rocking Curves

Three modes are available for Rocking Curve analysis: Evaluation and Fit, Evaluation, or Fit. The procedure differs only slightly from one to the other.

How to analyze Rocking Curves:

1. Load data
2. Configure sample model:
   1. Set substrate material and initial values.
   2. Add layers. Consider adding interface layers like native oxides.
   3. Set layer materials and initial values.
   4. Define Graded Layers if any.
   5. Define Super Lattices if any.
   6. Link layers (formula is of the type th[1] for linking thickness to layer L1)).
3. Set peak parameters and Evaluate:
   1. Associate peaks with layers or substrate.
   2. Select if the peak is a Bragg Peak or a Harmonic peak.
   3. For Harmonic peaks chose the harmonic order.
   4. When done press Evaluate to update fitting parameters.
4. Set X-ray parameters:
   1. Check values for wavelength and reflection.
5. Set simulation parameters:
   1. Select the scan type and the range for simulation.
   2. Click Auto in Horizontal transform to align the offset in 2θ.
   3. In Vertical transform, chose the background type and click "Auto" to add a background function to the simulation.
   4. Optionally add some of the values as fitting parameters.
6. Set fit algorithm and run fit
   1. Select the Fit method. Genetic Algorithm is for global optimization, while the two others are local optimizations.
   2. Change fit method parameters and settings as needed.
   3. Optionally set an instrumental function in the tab below the fit parameters window.

Reciprocal Space Mapping

For RSM data analysis use the RSM flow in the HRXDR plugin.

How to fit RSM data:

1. Load data:
   1. On the chart toolbar, plot options can be changed. Note that it is possible to change between angular and reciprocal space coordinates.
2. Smoothing and background subtraction:
   1. The data can be smoothed by weighted average of nearby neighbors.
   2. Background subtraction either in the form of a fitted background or a constant value is possible.
3. Search peaks
   1. Choose the settings for peak search.
   2. Verify the Peaks for Evaluation list.
4. Configure sample model:
   1. Set substrate material and initial values.
   2. Add layers. Consider adding interface layers like native oxides.
   3. Set layer materials and initial values.
   4. Define Graded Layers if any.
   5. Define Super Lattices if any.
   6. Link layers (formula is of the type th[1] for linking thickness to layer L1).
5. Generate hkl:
   1. Set the rotation angle, ϕ, of the substrate.
   2. Set the tilt of the substrate, χ, for an in-plane measurement, it is called 2θχ.
   3. Adjust the other parameters as wanted.
   4. Press "generate hkl".

For more information on how to use the HRXRD plugin, read the manual by clicking on the ? in the software or find it in LabManager - requires login.

RS viewer

The RS viewer (reciprocal space viewer) is an utility for simulating and viewing looking up theoretical 2θ angles and finding out how to position the goniometer for measuring in a skewed geometry. It can be opened from either the XRD Measurement tab (only on computers connected to a measurement tool) or from the HRXRD tab by clicking the button in the top ribbon.

In the RS viewer it is possible to make a sample model consisting of substrates and a number of layers on top. Unfortunately it is not possible to change the concentrations of different atoms in a composition as it is in the HRXRD sample building. But for each layer it is possible to change sample axis, e. g., changing the substrate normal from (0 0 1) to (1 1 1).

Using the RS viewer for setting up Reciprocal space mapping (RSM) is done in this way:

1. Sample:
   1. Change the substrate to the desired material.
   2. Check that 'Normal Sz' under 'Sample Axes' is correct.
   3. Add layers by right-clicking on an existing layer and click Insert New Layer.
   4. Configure the added layer(s) with the material type and expected orientation. If the material you want is not present in the database, see the Materials Manager section below for how to add materials.
2. Measurement:
   1. Choose the goniometer geometry desired for the measurement. Often In-plane is wanted to avoid tilting the sample.
   2. Choose if the reflection is symmetric or asymmetric for Out-of-plane (ω step).
   3. Choose Cu-Kα₁ as X-ray target
3. Reflection information:
   1. Select the layer for measurement.
   2. Select the reflection for measurement, either by clicking on the simulation map or by typing in the number. Only allowed reflections in the chosen geometry are shown.
   3. In the reflection box, information about the reflection, like 2θ, |F|, |F|² and the incident and reflected angles are listed.
   4. The five relevant axes for RSM configuration are listed below.
   5. Numbers at the left side of the slider are offsets needed for the measurement.
   6. To the right it is possible to choose if the measurement should be done relative to the offset or in absolute values.
   7. For the relevant axes, the measurement range can be set.
   8. At the bottom, "show area" will highlight the measurement area defined, and offsets can be sent to the goniometer, while areas can be sent to measurement configuration.

For more information please click on ? in the RS viewer window or see LabManager - requires login.

Texture

The texture plugin is used for Pole Figure analysis and Orientation distribution functions (ODF). However we do not have a license for ODF. To enable Orientation functions to be calculated, two or more pole figures are needed. The texture plugin has two types of calculations, a Defocusing project and texture calculation. The defocusing project will not be discussed here, as it is not strictly needed for the texture calculation, however the idea with this is to measure a substrate with randomly distributed crystals and subtract this from the oriented texture data.

A texture calculation is processed as follows:

1. Load data:
   1. Choose one or more pole figure data sets to load.
2. (Optional) Load defocusing project:
   1. This is only possible if a randomly oriented sample has been measured.
3. Configure sample:
   1. Set the material and the reflections that have been measured.
   2. Extra reflections and materials can be added by the "add reflection" and "add phase" tools.
   3. Also connect the reflections to the correct pole figures.
   4. When all materials and reflection is set, press Estimate 2θB, to calculate the 2θ angles.
4. Make pole figure corrections:
   1. Activate and change the settings of the preferred corrections in the right panel.
   2. Apply the corrections
   3. To read out the result, click on "orientation function" in the lower pane.

For more information on how to use the Texture plugin, read the manual by clicking on the ? in the software or see LabManager - requires login.

Powder XRD

For powder analysis licenses for Search/Match and Comprehensive analysis are available for SmartLab Studio II. If something more advanced like Rietveld refinement (WPPF) is needed, please use the software from HighScore from Malvern Panalytical, which is available in the equipment room 346-904, or as a remote session for one user at a time.

If only a simple analysis of the data is needed, please follow the guide below to use SmartLab Studio II on you own PC. To convert data from XRD Powder to enable loading in SmartLab Studio II please look here.

We have a separate page describing how to look up or add reference spectra from the Inorganic Crystal Structure Database (ICSD) (for DTU users and others with access to the ICSD).

Basic/Evaluation

The walk-through below is written for the RIR Quantification flow. If only Search/Match is wanted the evaluation flow has the same steps except the RIR part. The use of the plugin for basic analysis is as follows:

1. Load data:
   1. Data from XRD Powder has to be converted to .asc or .xy in advance.
2. Peak evaluation:
   1. Choose the settings for the peak search and profile fitting
   2. Press Run
3. Phase identification:
   1. To search for the peaks, press Search/Match in the left window.
   2. One of the best ways to limit the amount of data found is to use the element filter.
   3. "Material" can be set to unknown, not included, included, or include one at least by clicking on the materials several times.
   4. When the material filters are set correctly press "run" to search the database (see link above on how to add reference spectra to the database from the ICSD).
   5. The candidates found are listed in Phase identification window. The candidate with the smallest FOM/F20 is the most likely candidate to be present in the sample.
   6. Always use the prior knowledge of the sample to evaluate the outcome of the search.
   7. The identified phases can be moved to the candidate phase list, for use in RIR quantification.
   8. Press set above the candidate phase list before moving on.

Basic/RIR Quantification

For Reference Intensity Ratio (RIR) calculations, choose the RIR Quantification flow, which adds the following step to basic evaluation.

1. Configure RIR quantification:
   1. Chose the Miller indices to user for RIR.
   2. You can then right-click on the dataset below the RIR Quantification window and click "chart" to see the distribution of the phases.

Comprehensive Analysis/Crystallite size and strain

For comprehensive analysis, in the task drop down menu in the flow bar select Comprehensive analysis. Three flows are available here, Crystallite size and strain, Lattice parameter refinement, and Crystallinity.

For Crystallite size and strain the first steps are the same as for Search/Match evaluation and the following is added:

1. Configure size & strain:
   1. Select the dataset to analyse.
   2. Select or deselect peaks that are to be used or not for the calculation.
   3. Select the analysis method.
   4. Select 'Use e.s.d. for weight factor' (estimated standard deviation).
   5. Choose if width corrections is to be used.

Comprehensive Analysis/Lattice parameter refinement

For lattice parameter refinement, follow the steps for search and match. After phase identification do the following.

1. Configure lattice parameter refinement:
   1. Select the dataset to analyse.
   2. Select or deselect peaks that are to be used or not for the calculation.
   3. Select the angular correction to use.

Comprehensive Analysis/Crystallinity

For crystallinity calculation, follow the steps for search and match. After phase identification the following steps are needed.

1. Confirm crystallinity:
   1. Decide whether to include background.
   2. Choose if a line should be subtracted from the background.
   3. Select the target crystalline phase.

For more info on these steps, see the manual by clicking ? in the right panel for the plugin (Crystallite Size and Strain, Lattice Parameter Refinement, or Crystallinity) or see LabManager - requires login

Data Visualization

The data visualization plugin is mainly used to show data mapping. This could be data acquired with the xy-stage. 1D and 2D data are supported, and 1D graphs can be extracted from 2D plots. It further supports smoothing, background subtraction, and peak search for all loaded data sets in one go.

For more information click on ? in the software to right corner or see LabManager - requires login.

Data Manager

The data manager can be used for visualizing several datasets at once. As for the data visualization plugin, it support batch processing of data sets. Data comparison can easily be done and generates a great overview of differences and similarities between samples. It can also be used to concatenate data from several measurements into one data set, which is useful for data from the XRD Powder.

For more information click on ? in the software top rigth corner of see LabManager - requires login.

Materials Manager

The materials manager is used for adding crystal structures and amorphous material parameters for use in data simulation. For some users the compounds are of most interest, as it is in here that you can generate materials like In(x)Ga(1-x)As. Materials not listed can be added by either importing a cif file or defining it by hand. I (Kristian Hagsted) have found the homepage Materials Project helpful. See also the page on how to look up or add reference spectra from the Inorganic Crystal Structure Database (ICSD) (for DTU users and others with access to the ICSD).

We recommend downloading the symmetrized cif file for import. When adding materials please consider if the space group is the correct one. We would also prefer if the elastic stiffness tensor is entered into the software for all materials if available, which they often are on the Materials Project site.

For information about how to use the plugin please look in section 3.2 in the manual opened by clicking on the ? in the upper right-hand corner or see LabManager - requires login.