THE ATOMIC-STRUCTURE OF SIGMA=1 AND SIGMA=3 NISI2/SI INTERFACES

The high-resolution imaging technique is applied systematically to study the SIGMA = 1 (type A) and SIGMA = 3 (type B) NiSi2/Si interfaces. Possible structural models for SIGMA = 1 (type A) and SIGMA = 3 (type B) NiSi2/Si interfaces can be completely deduced from the dichromatic constrained coincidence site lattice (CCSL) patterns. For the SIGMA = 1 NiSi2(001)/(001)Si interface, new interface structures have been found and a 2 x 1 reconstructed interface structure involving a difference in composition has also been observed. The new interface structures were confirmed from through-focal series of high-resolution images from two orthogonal [110] beam directions. Domain-related interface structures coexisting in SIGMA = 1 NiSi2(001)/(001)Si interfaces were found to be separated by a 1/4[111] type of dislocation which is associated with a demi-step. There is only one interface structure observed in both SIGMA = 1 and SIGMA = 3 NiSi2(111BAR)/(111BAR)Si interfaces where the interfacial Ni atoms has been determined to be sevenfold coordinated. Two DSC dislocations associated with steps were identified in a SIGMA = 3 NiSi2(111BAR)/(111BAR)Si interface. The Burgers vectors of the DSC dislocations were determined to be 1/12[112BAR]Si and 1/3[111BAR]Si. Both DSC dislocations are associated with a complete step with the vector being 1/2[110BAR]Si. The long-period boundaries of SIGMA = 3 NiSi2(111BAR)/(115BAR)Si and NiSi2(221BAR)/(001)Si have been shown to decompose into short period of symmetrical NiSi2(111BAR)/(111BAR)Si and NiSi2(112BAR)/(112BAR)Si atomic facets which resembles the asymmetrical tilt grain boundary case. The coexistence of two domain-related atomic faceting interfaces in the SIGMA = 3 NiSi2(111BAR)/(115BAR)Si and NiSi2(221BAR)/(001)Si has also been observed in different areas of an interface. They are separated by a 1/4[111] type dislocation associated with a demi-step. The Burgers vector and step of a dislocation required to separate two domain structures and that of DSC dislocations in the SIGMA = 3 NiSi2/Si interface can be derived from consideration of the CCSL model.