PREPARATION AND GROWTH OF YSZ BUFFER LAYERS AND YBA2CU3O7 FILMS ON SILICON (100)

For the preparation of epitaxial high quality YBa2Cu3O7 - films on silicon substrates, Y-stabilized ZrO2 (YSZ) buffer layers turn out to serve as effective barriers against interdiffusion and show an epitaxial relationship with the silicon (100) single-crystal as well as the superconductor. A low temperature process to remove the amorphous native SiO2-layer before evaporation is of great importance. A chemical etching procedure leads to a very smooth and clean surface which can be stabilized and protected by either hydrogen or oxygen termination. The latter provides the advantage to persist nearly up to the deposition temperature of YSZ. The YSZ-layers were evaporated by an electron gun and characterized by X-ray diffraction as well as RHEED and SEM studies. Thereby we clearly observed epitaxial growth of smooth YSZ -layers. The subsequent YBa2Cu3O7 - films were epitaxially grown by reactive thermal coevaporation of the metals in an oxygen atmosphere, with critical temperatures of typically 87 K. Critical currents were determined up to 2 . 10(6) A/cm2 at 4.2 K and 8.5 . 10(4) A/cm2 at 77 K, respectively.