Role of film stoichiometry and interface quality in the performance of (Ba,Sr)TiO3 tunable capacitors with high figures of merit

Parallel platecapacitors with quality factors exceeding 1000 were fabricated using Ba0.3Sr0.7TiO3 (BST) thinfilms grown by hybridmolecular beam epitaxy on epitaxial Pt bottomelectrodes. The influence offilmstoichiometry was investigated by varying the (Ba + Sr)/Ti ratio around thestoichiometric composition. The quality factor is highest forstoichiometricfilms, but (Ba + Sr)-richfilms can be biased to higher fields. Furthermore, two different processes were used todeposit the topelectrodes of the parallel platecapacitors. While the quality of the top contact/BST interface did not strongly affect thedevice quality factor, an enhancement in thedielectric tunability was seen forcapacitors with topelectrodesdeposited at high temperatures, which effectively removes interfacial contamination layers.

Source: Applied Physics Letters - November 8, 2016 Category: Physics Authors: Christopher R. Freeze and Susanne Stemmer Source Type: research