Local nucleation and lateral crystallization of the silicide phases in the CoSi 2 buffer layer of YBa 2Cu 3O 7− x/CoSi 2/Si structure

Abstract

The phenomena of the local nucleation and lateral crystal growth of cobalt silicide phases have been investigated with the emphasis on a possible cause of the surface roughness and pinholes of the silicide layer. Local nucleation of the CoSi 2 grains on the structural defects of the silicon surface is found for the silicide films formed by vacuum annealing the Co/Si(100),(111) structure. Self-sustaining crystallization of the CoSi 2 phase around a crystal defect is observed. Lateral growth 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 CoSi 2/Si interface are much smoother if an additional zircon (Zr) layer is deposited onto the Co film before subsequent annealing. The CoSi 2 films were used as a buffer layer for the YBCO/CoSi 2/Si and YBCO/CeO 2/YSZ/CoSi 2/Si/Al 2O 3 heterostructures in this work. The superconducting transition temperatures of the YBCO films was found to be 86 K.