Microstructural Properties of Ba0.6Sr0.4TiO3/RuO2 Multi-Layers Grown on MgO and YSZ by Pulsed-Laser Deposition

The microstructure of Ba_0.6Sr_0.4TiO₃ (BST)/RuO₂ multi-layers grown on (100) MgO and (100) YSZ substrates, respectively, by pulsed-laser deposition (PLD) has been studied by transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM). The RuO₂ films deposited at 700°C adopt epitaxial relationships with both substrates. The epitaxial films on (100) MgO consist of two variants with an orientation relationship given by (110) RuO₂//(100) MgO and [001] RuO₂//[011] MgO. The epitaxial films on (100) YSZ contain four variants with an orientation relationship given by (200) RuO₂//(100) YSZ and [011] RuO₂//[001] YSZ. The BST films deposited on the RuO₂ electrode are epitaxial on the (200) RuO₂ films deposited on YSZ, and non-epitaxial on the (110) RuO₂ films deposited on MgO. The epitaxial relationship between the BST and (200) RuO₂ films can be described as (111) BST//(200) RuO₂ and [1&1macr;0] BST//[011] RuO₂. The BST films contain at least four variants. The growth and microstructural properties of the multi-layer structures can be understood based on geometrical consideration of the crystal structures.