INTERDIFFUSION OF Y-BA-CU OXIDES AND SIO2 SUBSTRATE - EFFICIENCY OF TITANIUM NITRIDE BARRIER FILM

Two kinds of reactively evaporated titanium nitride films with columnar (B0 films) and fine-grained (B+ films) structure have been examined as potential diffusion barriers preventing the interdiffusion of Y-Ba-Cu-O (YBCO) thin films and SiO2 substrates. This has been done at 600-degrees-C-a temperature compatible with semiconductor technology and sufficiently high to ensure crystallization of the superconducting 123 YBCO phase. Depth profiles of YBCO film and substrate constituents, established by RBS, enable quantitative estimation of the interdiffusion. Very high diffusivity of the SiO2 into the YBCO film has been found, compromising the quality of films with practical thicknesses. The titanium nitride B0 barrier diminishes the diffusivity by a factor of ten and so allows in situ YBCO film deposition on substrates of technological interest.