A low angle twist boundary formed by bonding an ultrathin (001) silicon film onto a (001) silicon wafer is investigated using two-beam transmission electron microscopy to identify positively zigzag lines which separate large interfacial regions formed by square networks of 1/2h110i screw misfit dislocations. An approach to the elastic field of a zigzag line is proposed from the repetitive use of angular dislocations added to a ribbon-like uniform distribution of infinitesimal dislocations parallel to a family of pure screw misfit dislocations. Theoretical and experimental images of successive triple nodes are compared to derive the unique set of Burgers vectors attached to a zigzag line. In principle, this approach can be applied to any elongated hexagonal mesh of a dislocation network.
A buried (001) low angle twist boundary (misorientation angle 0.48°) in silicon is 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 "relaxation centres" is assumed, for which the relative displacement field of the two crystals is zero. These centres are located in the middle of each square formed by a dislocation unit cell. This assumption is 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 is that of two perpendicular families of screw misfit dislocations in the sense of Bonnet (1981). Since the two-beam bright-field approximation is 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} have been 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.
Présenté par Jacques Villain
RésuméUne interface cristalline est souvent tapissée par un réseau dense de défauts linéaires dont la géométrie est (pseudo-) bipériodique. Le champ élastique de ce réseau est calculé en imaginant l'interface comme un pavage de dislocations de Somigliana adjacentes. Une analyse d'une portion de ligne zigzag erratique d'un sous-joint de torsion (001)Si, observée en microscopie électronique à transmission à deux ondes, est donnée en exemple.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.