Stress/Strain Fields at Interfaces
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Table 1195a lists the possible contrast mechanisms of bright-band in the Si (silicon) crystal at an a-SiO2/c-Si interface or an a-Si/c-Si interface in an ADF-STEM image. Table 1195a. Possible contrast mechanisms of bright-band of c-Si at a-Si or a-SiO2/c-Si interfaces.
Other factors such as sample thickness effect in zone-axis crystals [7] and detector inner angle, as shown in Table 1195b, may also affect the appearance of strain contrast in ADF images. In the existing of strain fields, the scattering of electrons results in different angular distributions and thus the intensity collected by the ADF detector from the strained region can be different than that from the strain-free region, resulting in strain contrast. The thickness dependence of strain contrast originates from the propagation process of the electron beam with the channeling effect [8-10, 1] inside a zone-axis crystal.
As shown in Figure 1195, when the strain amplitude increases, the channeling effect decreases, which is also called dechanneling. Therefore, the strain fields cause dechanneling.
[1] R. R. Vanfleet, M. Robertson, M. McKay, and J. Silcox, Characterization and Metrology for ULSI Technology (American Institute of Physics, New York, 1998), p. 901.
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