Dose-fractionated EELS spectrum image acquisition with direct detection cameras

Multi-frame spectrum image (SI) summation has been proposed and successfully demonstrated as a means of improving both scanning transmission electron microscopy (STEM) spectrum image resolution and signal-to-noise ratio (SNR) [1]. Scintillator-based CMOS and CCD detectors are inadequate for multi-frame electron energy loss spectroscopy (EELS) SI at low-dose and high speeds due to the detrimental effects of read noise. However, single-electron direct detection, counting cameras are capable of nearly noise-free readout, making them ideal for multi-frame EELS SI acquisition at low dose rate, as well as low total dose [2].

In this webinar, we demonstrate the capabilities of Gatan electron counting cameras, and eaSI™ technology, which together enable SI data capture at rates of up to 9,000 pixels/s. The near-zero read noise afforded by these cameras enables these ultra-high spectral rates to be utilized effectively, meaning a multi-frame acquisition approach is typically highly advantageous for all experimental workflows. Large field of view single SI passes can be acquired in just a few seconds, which gives the benefits of reduced dose rate data capture and high-frequency drift correction. Compromised data can be discarded post-acquisition, allowing “dose tuning” to be performed after the fact – ideal when you don’t know the critical damage dose ahead of time for total-dose sensitive samples.

A broad range of application examples using this methodology are presented, including elemental mapping in frozen cell sections (STEM cryo-EELS), electron energy loss near-edge structure (ELNES) mapping of transition metal K-edges (ultra-high energy-loss EELS), as well as atomic resolution EELS mapping of beam-sensitive oxides at low temperature (HR-STEM, cryo-EELS).

[1] Jones, L., et al., Microscopy 67. Suppl 1 (2018):i98-i113
[2] Goodge, B. H. et al., https://doi.org/10.48550/arXiv.2007.09747