Deposition and mechanical properties of polycrystalline Y2O3/ZrO2 superlattices

• Polycrystalline Y2O3/ZrO2 superlattice thin films were deposited using opposed-cathode reactive magnetron sputtering. Pulsed direct-current power was used to eliminate arcing on the metallic targets. Radio-frequency power was applied to the substrates to achieve ion bombardment of the growing film. In order to reproducibly deposit at high rates in Ar-O-2 mixtures, the Y target voltage was used to indirectly feedback-control the O-2 partial pressure. Deposition rates as high as similar to 70% of the pure metal rates were achieved, typically 3.5 mu m/h. Superlattices with periods ranging from 2.6 to 95 nm were deposited. Y2O3 layer thicknesses were either 75% or 50% of the superlattice period. X-ray diffraction and transmission electron microscopy studies showed well-defined superlattice layers. The ZrO2 layers exhibited the high-temperature cubic-fluorite structure, which was epitaxially stabilized by the cubic Y2O3 layers, for thicknesses less than or equal to 7 nm. The equilibrium monoclinic structure was observed for thicker ZrO2 layers. Nanoindentation hardnesses ranged from 11.1 to 14.5 GPa with little dependence on period. The hardness results are discussed in terms of current superlattice hardening theories.

Keyword

TECHNOLOGY

TEKNIKVETENSKAP

Publication and Content Type

ref (subject category)

art (subject category)