Technology

The core technology is an FEI Co. XL30 ESEM with a field emission gun (FEG). The ESEM detectors include a patented gaseous secondary electron detector (GSED), a solid-state backscattered electron detector (BSED), a large field detector (LFD), and a STEM detector for scanning transmission microscopy of embedded thin sections.

The ESEM can be used as a conventional SEM (high vacuum mode) or as an environmental SEM (wet mode, i.e. moderate vacuum and moist atmosphere). Wet mode is facilitated by flooding the sample chamber with water vapor and controlling condensation of the specimen surface via a temperature-controlled Peltier stage. Charging problems, common in materials with low electrical conductivity, do not occur because the water vapor neutralizes any charge that builds up on sample surfaces. Because sample drying and coating with a conductant are not necessary for wet mode, specimen preparation time is reduced, and biological samples and combined soft/hard matter can be imaged in their native state.

The ESEM is equipped with a Bruker energy-dispersive spectrometer (EDS) for X-ray microanalysis. The EDS has a QUANTAX XFlash 6|60 silicon drift detector (SDD) with energy resolution < 129 eV (MnΚα, 100 000 cps). ESPRIT microanalysis software is used for X-ray acquisition, qualitative and quantitative analysis, line profiles, and digital element maps (1, 2, 3).

The Quorum Technologies' Polaron PP2000T cryo stage extends MEIAF's ESEM capabilities to freeze-fracturing and ultra-low temperature imaging. With the cryo system, we can freeze and etch specimens, and maintain frozen samples at low temperature while imaging.

For more information on the ESEM specifications, please visit the manufacturer's website: www.feic.com/esem. For more on the EDS specifications, please see www.bruker.com/. The cryo stage manufacturer's website is www.quorumtech.com.