A buried (001) low angle twist boundary (misorientation angle 0.48°) in Si was investigated by the technique of two-beam transmission electron microscopy using bright-field images obtained from diffracting vectors g{400}, g{311} and g{220}, and g{nnn} with n = 3 and 4. To analyse its elastic field, the concept of interfacial so-called relaxation centres was assumed, for which the relative displacement field of the two crystals was zero. These centres were located in the middle of each square formed by a dislocation unit cell. This assumption was tested positively for the first time for a double periodic network of screw dislocations. For the image contrast calculations, the elastic field of the network was that of two perpendicular family of screw misfit dislocations in the sense of Bonnet. Since the two-beam bright-field approximation was weak to explain the experimental images taken with g{nnn} and n = 3 and 4, extra N beam image calculations involving N < 7 systematic reflections along g{nnn} were carried out with a devoted programme. All the computed images prove to be in good agreement with the experimental images, still validating the adopted elastic field.

Tests by TEM Contrast Simulations of the Elastic Field of a Buried (001) Low-Angle Twist Boundary in Silicon. A.Boussaïd, F.Fournel, R.Bonnet: Physica Status Solidi B, 2005, 242[15], 3091-8