Characterization of Ba 0.1Sr 0.9TiO 3/YBa 2Cu 3O 7– δ heterostructures on vicinal LaAlO 3 substrates

Abstract

Ba 0.1Sr 0.9TiO 3/YBa 2Cu 3O 7− δ heterostructure films have been fabricated by pulsed-laser deposition on LaAlO 3 substrates. During the fabrication, a c-axis oriented YBa 2Cu 3O 7− δ thin film with atomically smooth surfaces was epitaxially grown in the step-flow mode on a vicinal LaAlO 3 substrate. The superconducting transition temperature T c was above 88 K. Then a single-crystalline Ba 0.1Sr 0.9TiO 3 layer was deposited on top of the YBa 2Cu 3O 7− δ layer. A parallel-plate capacitor configuration was used to measure the capacitance–voltage properties of the Ba 0.1Sr 0.9TiO 3 thin films at 300 K and 77 K, respectively. The dielectric constant and loss tangent measured at 1 MHz and 77 K are 1200 and 0.0045, respectively. A tunability of 60% has been achieved under ±30 V DC bias, confirming their usefulness for frequency-agile microwave devices.