Origin of A- or B-type NiSii2 determined by in in situ transmission electron microscopy and diffraction during growth

In situ transmission electron microscopy during the growth of NiSi2 on Si by molecular beam epitaxy shows that the metastable phase, -Ni2Si grows at 300°C upon the reaction of certain deposited Ni films on (111) but never on (100) Si. Its existence correlates with the subsequent growth of type-A NiSi2 at 450°C. The low energy of epitaxial interfaces can influence phase formation in very thin films, leading to unusual thickness-dependent behavior such as the type-B type-A NiSi2 enigma.