Abstract text (incl. figure legends and references)

Introduction
Analytical Transmission Electron Microscopy is used for a wide range of applications. Usually TEM-experts perform most of the analytical techniques. However, easy access for non-expert users to different TEM methods is provided by ChemiTEM workflows [1]. These workflows are implemented in an app guiding the users step by step through the measurements. This enables non-expert users to perform standardised measurements including TEM imaging, STEM/HRSTEM and EDS. In addition in this work we present a workflow for measuring EELS-related techniques which includes measurement of sample thickness, mapping selected elements and investigation of the oxidation state of a material.

Objectives
As addition to the ChemiTEM app a workflow for EELS, aiming at the three most common measurement scenarios, is developed: Thickness measurement, elemental mapping and oxidation state determination. It guides the user step by step through the measurement procedures. This allows non-expert TEM users to perform these techniques, which increases the throughput for a research institute while maintaining a high standard in data quality and comparability.

Methods & Results
To assess which EELS techniques are mostly used, the EELS measurement tasks of 9 months at the Max Planck Institute for Chemical Energy Conversion have been evaluated and rated with respect to the demand on the TEM operator. Out of 54 samples 29 needed EELS elemental mapping as well as oxidation state determination, while 25 required thickness evaluation.
In the EELS workflow a first set of questions about the sample helps the user to judge whether a measurement can be successfully performed by a non-expert user. A decision-tree based based workflow (Fig. 1) guides the user through sample preparation, choosing a suitable measurement region, alignment of the spectrometer including safety precautions for the camera and acquisition settings to achieve a good signal to noise ratio of the desired signal. The workflow distinguishes between the three scenarios mentioned before: For thickness measurements the focus lies on acquisition of the zero loss peak and low loss region as well as camera protection. For elemental mappings the workflow helps to determine which parts of the spectrum to acquire with respect to dispersion and drift tube voltage in a window between 200 and 1200 eV. Finally, for the oxidation state investigations the acquisition of the oxygen K edge and the zero loss peak in case of dual EELS measurements are covered in the workflow. In each case data analysis using appropriate software packages is also included.
The presented EELS workflow is tailored for a FEI Talos F200X microscope equipped with a Gatan Continuum S spectrometer, however, it can be adapted to other setups with minor effort.
To assess the designed EELS workflows, users which were trained using the ChemiTEM workflows and an experience of less than 10 sessions, more than 20 sessions and an expert TEM user evaluated the same sample and the results have been compared.

Conclusion
The large amount of training an expert TEM user needs cannot be replaced, but parts of the tasks that can be performed in a standardised way can be carried out by non-expert TEM users using our EELS workflow, making this sophisticated TEM technique available to a larger community.

[1] Hetaba et al., Chemistry-Methods 2021, 1, 401-407

Fig.1: Schematic decision-tree of the ChemiTEM EELS workflow.