Chemical and Structural Characterization of TEM Windows

A TEM image of a fOO-nm thick cross-section of a TEM membrane prepared by microtome slicing is shown in Fig. 4.25 [125]. The membrane thickness 

A diagonal scan across the surface of the window was recorded with X-ray energy dispersive spectroscopy (XEDS) in the TEM equipment. The atomic ratios of Si 0 N were found to be 43% 13% 44%, which is not the expected stoichiometry of Si02 and Si3N4 (40% 20% 40%). However, we know from the TEM images and the SIMS data shown below that the thickness of the oxide layer is 7 nm and the total window thickness is about 42 nm from which we would expect atomic ratios of 42% 8% 50%. This is most likely indicative of a native oxide present on the backside of the windows, enriching the O content of the whole film (as seen with SIMS), since the escape depth of the photons is much greater than the window thickness. 

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