Microstructure of sputter-deposited strontium titanate films

The origin of a marked difference in a dielectric constant, κ, observed between two types of strontium titanium oxide (STO) films sputter-deposited on platinum layers was investigated using a transmission electron microscopy method. The first type of STO films having a low κ value initially grew as an amorphous phase, followed by the formation of a randomly oriented polycrystalline phase. The second type with a high κ, on the other hand, not only grew as a crystalline phase throughout the entire film thickness, but also exhibited a strong [111] fiber texture. The observed difference in κ between these two types of STO films can thus be explained in terms of the degree of film crystallinity and texture.