A tunable high-Q flexible ferroelectric film capacitor for GHz RF applications

With the development of flexible electronics, flexible tunable capacitors with high dielectric constant, high tunability, and low loss become important components in modern communication. A tunable Ba0.6Sr0.4TiO3 capacitor for radio frequency devices is prepared on a flexible substrate. The capacitor has a dielectric constant greater than 1000, capacitance tunability n exceeding 70%, and minimum loss tangent lower than 0.03 at 500 kHz. The Q factor can be above 10(3) at the GHz frequency range. These parameter values (especially the Q factor) have been comparable to the rigid substrate tunable capacitor. Meanwhile, the minimum radius of curvature of the flexible tunable capacitor can be 3 mm with stable electrical performances. The flexible tunable capacitor retains its mechanical and electrical stability after 24 000 high-frequency bending cycles, which provides potential uses in bendable, collapsible tunable capacitors at the radio frequency range.