Epitaxial growth of YBa2Cu3O7−x thin films on Si(100) with zirconia buffers of varying crystalline quality and structure

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Abstract
Thin epitaxial films of monoclinic pure and cubic yttria‐stabilized (YSZ) ZrO2 were deposited onto Si(100) by electron‐beam evaporation. The degree of crystalline perfection was controlled by the growth temperature. Epitaxial YBa2Cu3O7−x films were grown on these buffer layers by KrF excimer laser ablation. Optimum crystalline and electrical quality, characterized by a transition temperature Tc0 of 86–89 K, a critical current density jc of 106 A/cm2 at 77 K, and a channeling minimum yield of 12% was obtained on YSZ buffers showing a minimum yield of 7%. Even a 14‐nm‐thick YSZ buffer enabled the growth of an YBa2Cu3O7−x film with Tc0 of 86 K and a minimum yield of 12%. With decreasing quality of the YSZ buffer layers the crystalline quality of the superconductor also decreased. The disorder in the YBa2Cu3O7−x films, however, increased more slowly than in the buffer layers, so that even on an amorphous buffer the YBa2Cu3O7−x exhibited a pronounced texture with a minimum yield of 72%. The comparatively rough surface of the monoclinic pure ZrO2 severely hampered the c‐axis alignment of the YBa2Cu3O7−x, resulting in superconductor films of inferior quality.