Obtaining CBED Patterns

Abstract

We know that SAD, while giving us useful information about the specimen, has two severe limitations. & We have to be very cautious in interpreting SADPs from areas which are < 0.5 mm in diameter because the information in the pattern may not be limited to that region. This scale is still large compared to the dimensions of many crystalline features that interest us in materials science and much larger than nanotechnology dimensions. & SADPs contain only rather imprecise 2D crystallographic information because the Bragg conditions are relaxed for thin specimens and small grains within the specimen (see Chapter 17). The technique of CBED overcomes both of these limitations and also generates much new diffraction information which we will introduce to you in Chapter 21 and expand in greater depth in the companion text.