In-Situ Transmission Electron Microscopy of MBE NiSi2 or CoSi2 Formation

In a modified high resolution transmission electron microscope we are able to study the Molecular Beam Epitaxy (MBE) of thin NiSi2 or CoSi2 layers on clean Si surfaces. A non-uniform structure exists after room temperature deposition of ~10A layers of Co (or Ni). On annealing these deposited Co layers, Co2Si is seen to form below 400 degrees C and CoSi2 nucleation, at over 550 degrees C is preferred at surface steps. Growth of CoSi2 is by an island mechanism. The observations explain several previously observed microstructural details of thin CoSi2 layers and Si/CoSi2/Si heterostructures which have important implications on electronic properties. Results on NiSi2 formation will also be presented.