Cross-Sectional Tem Studies of Barium Strontium Titanate Deposited on Silicon by Pulsed Laser Ablation

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Abstract
Barium strontium titanate films were deposited onto silicon substrates using pulsed laser ablation deposition. The films were characterized using conventional and high resolution cross-sectional TEM. It was found that the grains were columnar with an average width of approximately 23 nm. An amorphous interfacial layer formed between the Si and BST in all cases. The interfacial layer thickness increased as the sample exposure to O2 increased. TiSi2 was also observed in all the films, although its location at the interface was not directly verified. There are no systematic effects of O2 overpressure on either the film thickness or film microstructure. However, the film which was fabricated with the greatest exposure to O2 may contain TixOy, and contains more equiaxed grains than the other samples. An interfacial layer was also observed at the Au-Pd/BST interface in a metal/ferroelectric/silicon capacitor. The significance of the results is the observation that BST may never come in direct contact with either capacitor electrode, which may explain why the fatigue behavior and electrical characteristics of ferroelectric capacitors depend so strongly on the interfaces.

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