INTERFACIAL DEFECTS IN SILICIDES ON SI(100) - CORELESS DEFECTS, 1 12(111) DISLOCATIONS, AND TWINNING MECHANISMS/

''Coreless defects'' are one of the long-standing surprises of silicid e epitaxy on Si. or symmetry reasons a NiSi2 or CoSi2 film cannot grow over a step on Si(100), but must incorporate a dislocation; apparentl y, however, very thin films avoided this dislocation by introducing a trench through the silicide, the coreless defect. Here we use high-res olution microscopy, electron diffraction and dark-field imaging to sho w that these defects are in fact microtwins almost-equal-to 4 atomic p lanes thick. The twins are highly unusual in that they follow curved l ines, apparently dictated by steps at the interface. A mechanism for t he formation of these curved twin defects by repeated formation of a 1 /12[111] interfacial partial at steps is postulated.