LOCAL NUCLEATION AND LATERAL CRYSTALLIZATION OF THE SILICIDE PHASES IN THE COSI2 BUFFER LAYER OF YBA2CU3O7-X COSI2/SI STRUCTURE/

The phenomena of the local nucleation and lateral crystal growth of co balt silicide phases have been investigated with the emphasis on a pos sible cause of the surface roughness and pinholes of the silicide laye r. Local nucleation of the CoSi2 grains on the structural defects of t he silicon surface is found for the silicide films formed by vacuum an nealing the Co/Si(100),(111) structure. Self-sustaining crystallizatio n of the CoSi2 phase around a crystal defect is observed. Lateral grow th of the silicide crystallites from the Si crystal defects indicates that the lateral growth mode is preferable for the silicide phases at the Co-Si interface. The silicide film surface and CoSi2/Si interface are much smoother if an additional zircon (Zr) layer is deposited onto the Co film before subsequent 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 work. The superconducting transition tempera tures of the YBCO films was found to be 86 K.