LOCAL NUCLEATION AND LATERAL CRYSTALLIZATION OF SILICIDE COBALT PHASES AT INTERACTION OF COBALT FILM WITH SILICON SURFACE

The phenomena of local nucleation and lateral crystal growth of cobalt silicide phases have been investigated with emphasis on a possible re ason of the surface roughness and pinholes of the silicide layer. Loca l nucleation of the CoSi2? grains on the structural defects of the sil icon surface is found for the silicide films formed by vacuum annealin g the Co/Si(100),(111) structures. Self-sustaining crystallization of CoSi2 phase around a crystal defect is observed. Lateral growth of the silicide crystallites from the Si crystal defects, on the Co-patterne d step edge and SiO2: island steps, indicate that the lateral growth m ode is preferable for the silicide phases at Co!Si interface. The sili cide film surface and CoSi2/Si interface are much smoother if an addit ional zircon (Zr) layer is deposited onto the Co film before subsequen t annealing. The CoSi2 films were used as a buffer layer for the YBCO/ CoSi2/Si and YBCO/CeO2/YSZ/CoSi2/Si/Al2O3 heterostructures in this wor k. The superconducting transition temperatures of the YBCO films were obtained to be up to 86 K. (C) 1998 Elsevier Science S.A. All rights r eserved.