What is STEM?
As with conventional Transmission Electron Microscopy (TEM), in STEM mode the electrons pass through a sufficiently thin specimen. However, in STEM mode the electron beam is focused into a narrow spot that is scanned over the sample in a raster pattern. STEM is more efficient than a conventional TEM for dark-field imaging, allowing high contrast imaging of biological samples without requiring staining.
The STEM detector on the Nano NovaSEM 650
The STEM 3 detector has eight individual channels: three concentric, ring-shaped segments, of which the outer is divided into six segments. The retractable STEM 3 detector enables scanning transmission imaging in bright field, dark field and high-angle dark ﬁeld modes. With the retractable STEM 3 detector there is no need to vent the chamber to insert or remove the detector. The detector includes a special sample holder that can hold up to six TEM grids. High-vacuum imaging, optimum working distance for STEM: 0.8 nm at 30 kV.