The application of HRTEM to the study of equilibrium segregation in linear and planar silicon defects is evaluated with image calculations. For this purpose, models for interstitial segregation in the Σ=9 grain boundary and donor segregation in the 30° partial dislocation are proposed. These models possess columns of impurity atoms.
Systematic image simulations were first examined for an impurity column in an otherwise perfect <110> silicon crystal. Optimum contrast and exposure times require samples of thickness equal to the transmitted beam extinction distance. Arsenic and boron are detectable with a column concentration of about 5%. With diffuse phase contrast imaging, this limit is roughly halved.
The above imaging conditions may be used to distinguish different defect core models.
Observation of segregated impurities requires somewhat higher concentrations in addition to image comparisons with a clean defect. Quantitative analysis necessitates careful image simulation comparisons and improvements in knowledge of microscope parameters.