To enable and improve the imaging of samples in the electron microscope they need to be conductive. This can be achieved by sputter coating, carbon coating or e-beam coating. Also protection of the sample, enhancing the contrast and preparation of grids, to name a few, require coating technology. A range of coating techniques can be applied, depending on the sample and its preparation for analysis. A dedicated instrument combining coating under cryo conditions and a cryo knife to break a sample, opens the route to freeze fracture applications.
From low vacuum room temperature coating to high vacuum cryo coating, Leica Microsystems covers the complete range of needs for coating.
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A sample is coated with either a conductive layer of carbon or metal to inhibit charging, to reduce thermal damage and to improve the secondary electron signal for topographic examination in the SEM. For TEM analysis of samples, carbon coated grids are used or the sample itself might need a thin layer of coating on top.
Leica Microsystems’ coater line comprises the Leica EM ACE600 high vacuum coater for highest resolution analysis in FE-SEM and TEM and the Leica EM ACE200 sputter and/or carbon thread coater as a fully automated system for fast, convenient and intuitive handling.
To reveal internal structures of a frozen specimen, it can be physically broken to expose those structures for examination with an electron microscope. The Leica EM ACE900 cryo coater brings the freeze fracture technique to a new level, featuring an advanced microtome, flexible shadowing options with electron beam sources, a rotating cryo stage and a load-lock transfer system. High resolution analysis of replicas in the TEM and, equipped with the Leica EM VCT500, block face imaging in the cryo SEM are the results of this technique. The Leica EM ACE600 equipped with a cryo stage and a VCT500 connection provides a solution for freeze fracturing to image the revealed surface in a cryo SEM.
Freeze etching is an optional step after freeze fracturing the sample and reveals more information from the fractured faces. This is achieved by sublimating superficial ice layers under vacuum to expose cellular elements that were originally hidden. Stage temperature and vacuum are influencing the etching rate. Accurate temperature control of the stage is required to achieve reproducibility. As a highly versatile instrument the Leica EM ACE900 cryo coater offers best results for freeze fracture and freeze etching techniques for TEM, and cryo SEM analysis.