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The structure of multilayered coatings is studied by a combination of low voltage SEM, cross-sectional TEM and AFM. Specimens for SEM can be rapidly and conveniently prepared by fracturing the substrate; this technique works most successfully for brittle substrates such as glass or silicon. Cross-sectional TEM specimens are prepared by embedding in epoxy or a notched steel cylinder, slicing with a diamond saw, mechanically polishing and ion beam milling to electron transparency. The procedure can also be adapted to cross-sectional SEM specimens prepared by reducing the final ion beam thinning time. Specimens with abrupt changes in surface height, such as steps or deep troughs, tend to be unsuitable for AFM because of the risk of introducing image artefacts or causing tip damage. A more suitable method for studying multilayer structures was found to be production of a low angle tapered section by shielding a portion of the substrate with a glass square during deposition. The major advantages of this approach are that no additional specimen preparation is subsequently required and that depth resolved X-ray microanalysis can be carried out by stepping the probe along the wedge. Accurate knowledge of the wedge angle is required in order to relate the observed layer spacings to the real structure. Interpretation of the AFM images is assisted by the presence of atomic number (Z contrast) effects analogous to those in the SEM. Examples will be described of the application of these techniques to investigation of growth defects, interface roughness, interlayer diffusion and phase modifications.

Additional information

Authors: RICKERBY D, JRC Ispra (IT)
Bibliographic Reference: Paper presented: MC 95, Colmar (FR), May 10-12, 1995
Availability: Available from (1) as Paper EN 38971 ORA
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