Researches on Tunable BST Capacitors Under Electricity and Stress Fields

In the paper, tunable Ba
_0.5
Sr
_0.5
TiO
₃
(BST) varactors on LiNbO
₃
substrates were investigated by changing electricity and stress fields applied to the BST varactors. The BST films were fabricated by RF Magnetron Sputtering on LiNbO
₃
substrates and the XRD of films showed high crystal quality on (110) surface. We demonstrate that the capacitance tunability can each 1.67 under applied DC voltage from 0 to 8V. Additionally, the tunability can be 1.46 by changing stress from 0 to 7. 2MPa. Interestingly, the tunability is 2.45 under the combinations of electricity and stress fields. This phenomenon implies that the applied dynamic stress can break restrictions in the limitation of the capacitance tunability of this thin film. It is of great significance to observe the direct relationship between the change of strain and dielectric tunability caused by stress fields, which can provide more ideas for the design of thin films varactors in future applications, such as tunable SAW filter, microwave delay line and acoustic stress sensor, etc.