XTEM/SAED and SNMS study of film/substrate reactions in Bi 2Sr 2CaCu 2O y films on Si(100) with Si 3N 4 buffer layer

Abstract

We have performed cross-sectional TEM/SAED and SNMS studies of film/substrate interactions in Bi 2Sr 2CaCu 2O y (“2212”) films on Si(100) substrates using Au, SiO 2, and Si 3N 4 buffer layers. The 2212 films were prepared by electron beam evaporation of stoichiometric targets in O 2 of 2×10 −4 mbar and post-annealed in air at 800/850 °C. SNMS depth profiles indicated Si 3N 4 layers to be most effective of the buffers studied; they enabled us to grow c-axis oriented 2212 films. These, however, were not superconductive. XTEM and SAED revealed a strong attack on the Si 3N 4 buffer layer by solid state reactions resulting in a severe roughness of the initially plane interface. The induced roughness of the interface obviously is responsible for the observed deviations (up to 20°) of the c-axis of the 2212 grains from the substrate normal, which in turn lead to weak links. The latter then probably inhibit superconductivity.