A scanning transmission electron microscope is a conventional transmission electron microscope equipped with additional scanning coils, detectors and necessary circuitry.
As with conventional transmission electron microscopy (TEM), images are formed by electrons passing through a sufficiently thin specimen, however, in scanning transmission electron microscopy (STEM) the electron beam is focused to a fine spot which is then scanned over the sample in a raster. This is similar to how scanning electron microscopy works. By rastering the beam across the sample, STEM is suitable for analytical techniques such as energy dispersive spectroscopy.
STEM also offers a number of potential advantages over TEM imaging for tomography of biological specimens. A practical advantage of STEM is its capacity to generate contrast without the need for defocusing. The scanning geometry of STEM also allows for dynamic focusing so that the imaging conditions remain uniform across a tilted specimen. STEM has been demonstrated to allow tomography of thicker sections with improved signal-to-noise ratio and contrast over conventional TEM tomography. This has significant potential for understanding subcellular organisation and organelle-organelle interactions at the nanometre scale through a whole cell volume.
STEM tomography is a new and emerging technique in life science research. We are collaborating with leading international groups to advance this technique and understand its full potential.