Dave Mitchell's DigitalMicrograph™ Scripting Website

Function

Allows a dataset of 110 STEM probes (full width half and tenth maximum (FWHM & FWTM), and current) to be searched on the basis of either target probe characteristics or microscope settings (Gun Lens, Spot Size and C2 Aperture) from which they are derived. This dataset is unique to the FEI Osiris (X-FEG source, analytical polepiece, 200kV).

Version

version:20130210, v1.0

Author

D. R. G. Mitchell.

Acknowledgements

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Comments

This script contains STEM probe data for all the realistic combinations of Gun Lens (4-8), C2 Aperture (50 and 70um) and Spot Size (1-11) for the FEI Osiris TEM (analytical polepiece, 200kV). This constitutes 110 different probes. The probe dimensions and current have been measured at each combination of settings by switching the STEM out of Diffraction mode and capturing an image of the probe on a GIF. The probe was stigmated and the Rotation Centre corrected at each setting. A live intensity profie was set up in View mode with an integration width of the height of the CCD image. This produced a live intensity profile of the probe. This was used to focus the probe - the focus being that which gave the maximum peak intensity. Images were saved and the analysis done offline using the Probe Analyser script - also available here. This automatically computes FWHM, FWTM and a number of other parameters including probe current, based on the CCD counts to electrons calibration. The current displayed on the FEI FluCam screen is reported here. The CCD measured current was always a factor of ca 2 lower. Until I do a Drift Tube current measurement, I do not know which is the more accurate, but since the FluCam current is readily accessible, it is reported here. The Osiris is based on the Tecnai column, but has an X-FEG source, whereas FEG Tecnais have an S-FEG source (I believe). This means that the values reported herein are only likely to be valid for other Osiris instruments and not the whole Tecnai range. However, you can still use it as an interactive tool to understand the effects of Spot Size, Gun Lens and C2 Aperture on the probe size and current in general. The C1 aperture was set to 2000um throughout, but even when the smallest (30um) C1 aperture was inserted, it had no effect on probe shape or current.

When launched a small help file is printed in the Results window, which explains how to use the script.

If you have an equivalent large dataset of probe measurements for another type of microscope you can modify this script directly to mine that data. If you need assistance, contact the author.

System Requirements

Compatible with GMS 1.x and 2.x. Ouput data are likely to be valid only for FEI Osiris TEMs.

Known Issues

The FluCam screen current reported here is an unknown. FEI say it is factory calibrated, but I have no calibration data. The value is that read directly from the User Interface program - no backscatter or other corrections have been applied.

Supported

Yes.

Included Files

Script File.

Source Code