Transmission electron microscopy
Transmission electron microscopy (TEM) is a high-resolution imaging technique in which a beam of electrons passes through a thin sample to produce an image. The electron beam is impacted by the sample’s thickness/density, composition, and in some cases, crystallinity. The electrons that are transmitted through the specimen subsequently provide contrast in the resulting image.
TEM is capable of unparalleled resolution due to the small wavelength of the transmitted electrons. Unlike scanning electron microscopy (SEM), which gathers the net intensity of secondary electrons in each point of the scan, TEM resolution is only limited by the wavelength of the individual electron and the quality of the electron optics. This means that transmission electron microscopes can routinely collect sub-nanometer scale (if not atomic-resolution) images.
Scanning transmission electron microscopy
Scanning transmission electron microscopy (STEM) combines the principles of transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Like TEM, STEM requires very thin samples and looks primarily at beam electrons transmitted by the sample. One of STEM’s principal advantages over TEM is that it enables the use of other signals that cannot be spatially correlated in TEM, including characteristic X-rays and electron energy loss spectra (EELS).
Like SEM, STEM scans a very finely focused beam of electrons across the sample in a raster pattern. Interactions between the beam electrons and sample atoms allows for simultaneous acquisition of multi-modal data, which is correlated with beam position to build a virtual image in which the signal level at any location in the sample is represented by the contrast of the image. Its primary advantage over conventional SEM imaging is the improvement in spatial resolution.
With STEM, extremely localized analytical data can be collected for your sample. This includes large-area, high-resolution energy-dispersive X-ray spectroscopy (EDS) maps, probing of oxidation states using EELS, and atomic-resolution imaging of material interfaces.
Cryo-transmission electron microscopes
Cryo-electron microscopy (cryo-EM) describes an increasingly popular group of life science techniques including single particle analysis, micro-electron diffraction, and cryo-tomography. Cryo-EM is performed on cryo-transmission electron microscopes (cryo-TEMs), which are specialized TEMs designed to operate at cryogenic temperatures. They typically feature modifications to sample loading, the sample chamber, and the sample stage to maintain the required temperatures and to reduce sample contamination and damage.
Transmission electron microscopes
Thermo Fisher Scientific’s TEM product line features enhanced imaging and analysis through simplified/automated operation, offering higher data quality and faster acquisition times. It also combines outstanding high-resolution STEM imaging with unparalleled advances in EDS signal detection for compositional mapping and 3D chemical characterization with the Thermo Scientific Dual-X, Super-X, and Ultra-X EDS Detectors. Thermo Scientific TEM platforms are suited for multi-user and multi-discipline environments, combining multiple applications in a single system.
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