TechnicalRemarks: The data contains Digital Micrograph files in the .dm3 and .dm4 formats and Velox files in the .vmd format. Digital Micrograph (DM) data can be open either by installing the offline and free version of the DM software from the Gatan website or by using the open access Fiji software. Velox data can be open with a special script available for DM.
Experimental details:
In order to perform TEM measurements the sample was prepared inside an argon field glovebox and then transferred to the microscope using a vacuum transfer holder in order to prevent samples from extensive air exposure. The dry powder of the samples was directly dispersed on the TEM holey carbon membrane without the use of solvents. The measurements were performed using a double aberration corrected and monochromated Themis Z microscope equipped with a Gatan GIF Continuum 970 spectrometer and a K3 IS camera. High-resolution STEM-HAADF images were recorded using a collection angle range of 63-200mrad. EELS spectrum imaging data cubes were acquired with a probe convergence angle of 30 mrad and a probe current of 0.5nA. The pixel size was around 1 nm and a dwell time of 0.1s per pixel for all the data series. The camera length was 30 mm and the spectrometer aperture was set to 5 mm resulting in a collection angle of about 40 mrad. All EELS data was acquired in dual-EELS mode containing both the core loss and the low loss spectra. All core loss spectra were realigned and deconvoluted based on the low loss spectra pairs prior to any data analysis.
