Ice Contamination
Figure 6: Results of the Ice Contamination Survey to the question “How does ice contamination impact your research?”
Figure 8: Results of the Ice Contamination Survey to the question “Which of these problems have you encountered?”
without moisture. Moreover, according to our survey, less than 20% of the laboratories are equipped with a low humidity room. When users transfer samples from one device to another,
the commonly used transfer devices operate at a low vacuum (around 1 × 10-2
to 1 × 10-3 mbar), and the residual moisture in
the device can condense on the vitrified sample surface and form amorphous ice contamination. An overwhelming 44% of our survey participants found transfer steps problematic. Dur- ing the transfer, the sample can also devitrify if it is not kept below -140˚C. Te devitrification issue affected 15% of our sur- vey participants. How do crystalline ice contamination and devitrification
Figure 7: Results of the Ice Contamination Survey to the question “Which stage of the lamella preparation process is particularly problematic for you?” FIB, focused ion beam; SEM, scanning electron microscope.
2022 May •
www.microscopy-today.com
affect cryo-ET data quality? Cryogenic samples are typically coated with a thin layer of platinum for protection from ion beam damage prior to lamella milling. Te crystalline ice par- ticles can lead to an uneven platinum deposition, resulting in an artifact known as curtaining, which was experienced by 16% of our survey participants (Figure 8). If the ice particles detach from the sample, they leave unprotected spots, which result in lower-quality lamellae and lower TEM image quality. Ice crys- tals on the lamellae and devitrification obscure the ROI in the TEM, thereby preventing collection of useful data [10].
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