High-resolution mode, electron microscopes

HRTEM images were obtained on a Jeol JEM2010 ultra high-resolution analytical electron microscope equipped with an emission cathode operated at 200KV in bright field mode. The samples were examined with a magnification of 400,000. The ex situ treated samples were supported holey carbon coated copper grids for the experiment. 

Single-walled carbon nanotubes (SWNTs) obtained in the Rice University, Houston, were investigated in high resolution mode (0.335 nm) using a Philips 420 transmission electron microscope. Digital images were captured at the atomic lev-... 

Figure 31. Schematic of the beam path in an electron microscope according to the geometrical optics approximation A) High-magniflcation, high-resolution mode B) Selected area diffraction mode...

Another large instrument with emphasis on high transmission at high resolution for isotopic measurements in geological applications is the IMS 1270 [60]. This instrument is similar in design to the IMS-3f and other Cameca f-series instruments but is much larger. It operates in either microprobe or microscope mode. Four auxiliary detector assemblies, containing an electron multiplier or Faraday cup plus the central beam primary detector, provide simultaneous detection of five isotopes. 

It is possible to distinguish between two modes of transmission electron microscopy depending on the type of sample illumination parallel beam or focused probe. These two modes, corresponding to high resolution imaging and microanalysis, arc now often combined in the same microscope using computer controlled lenses. 

Resolution in the STEM is limited by the probe diameter, which is about 1 nm in equipment dedicated to this operating mode, at the cost of using a cold field emission gun requiring an ultravacuum. Because of the high-precision optics and the point-by-point image formation principle, the STEM combines the advantages of scanning electron microscope analysis with resolution performance levels similar to the transmission electron microscope. 

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