With rapid advances in flexible electronics and communication devices, flexible dielectric capacitors exhibiting high permittivity, low loss, and large electric-field tunability over a wide frequency range have attracted increasing attention. Here, a large-scale Ba0.67Sr0.33TiO3 (BST) dielectric thin film sandwiched between SrRuO3 (SRO) bottom electrode and Pt top electrode is fabricated on a flexible mica substrate. The mica/SRO/BST/Pt capacitor exhibits a dielectric constant (εr') of more than 1200, a loss tangent [tan(δ)] as low as 0.16, and a tunability of 67% at low frequencies around 10 kHz. Simultaneously, the capacitor can retain an εr' of 540 and a tan(δ) of 0.07 at microwave frequencies, e.g., 18.6 GHz. Moreover, even when the capacitor is bent to a small radius of 5 mm or undergoes 12 000 bending cycles (at 5 mm radius), almost no deterioration in εr', tan(δ), and tunability is observed. The excellent dielectricity and mechanical flexibility and durability endow the mica/SRO/BST/Pt capacitor with huge potential for flexible electronic and microwave applications.
Keywords: (Ba,Sr)TiO; dielectricity; flexible capacitor; mica; microwave frequencies.