Epitaxial Dielectric Planarization for Multilayer HTSC Structures

Yttria-stabilized ZrO2 (YSZ) and CeO2 thin films were deposited on patterned (001) YSZ and (001) LaAIO3 substrates, respectively, using ion beam assisted deposition (IBAD) at normal incidence and an ion beam energy of 500eV. All deposition took place at 600°C. An initial 1000A thick layer was evaporated at 0.2A/s before beginning IBAD at rates of 0.3A/s for YSZ and between 0.8A/s and 1.2A/s for CeO2. X-ray diffraction shows the YSZ films to grow epitaxially. The planarization mechanism for IBAD YSZ is similar to that previously observed for if-bias sputtering. CeO2 grows epitaxially on LaA103 but a second polycrystalline phase grows preferentially over the surface steps and inhibits the planarization process. The emergence of this phase appears to be related to highly incoherent growth of CeO2 over the stepped edges, which in turn is a function of the large lattice mismatch between CeO2 and LaA1O3 in the [001] direction.