Superconductor/ferroelectric (SF) and normal conducting metal/ferroelectric (NF) film structures were grown using DC and RF magnetron sputtering of ceramic YBa2Cu3O7-delta and BaxSr1-xTiO3 targets. Low-energy ion beam etching was used for patterning an SF planar capacitor with an electrode gap of about 1.5 mu m. Ferroelectric films displayed a rather smooth temperature dependence of epsilon with a maximal value of about 850 at T similar to 260 K (tan delta similar to 0.02). Planar ferroelectric capacitors were intended for application in microwave tunable devices, so structures without hysteresis in voltage-capacitance characteristics were demanded. The SF and NF structures demonstrated a high enough coefficient of capacitance tuning (more than 1.5) and lower hysteresis for structures with YBCO electrodes. [References: 12]
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