Abstract
High-resolution electron microscopy observations have been performed on nickel silicide (Nisi2) precipitates in the ∑ = 25 grain boundary area of silicon bicrystal. The two orientation relationships type A and type B, usually encountered in monocrystalline silicon, have been recognized with respect to one of the grains. Details of the silicide/silicon interface structures are reported. In addition to most of the interfaces previously observed in the case of epitaxial growth, we have found evidence of two new ∑ = 1 Si(111)/(111)NiSi2 atomic structures. The interfacial Ni atoms, belonging to both new structures, have been determined to be sevenfold and eightfold coordinated. The growth of precipitates has been found to occur along the (111) planes, but ending by steps. For type A precipitates, 1/2[100] complete steps with the vector 1/2[101] have been identified while type B precipitates have 1/3[111] steps associated with a vector of 1/2[110].
