Tunability of YBa sub(2)Cu sub(3)O sub(7)/SrTiO sub(3) hetero-structures for microwave filters: Growth parameter optimization of the titanate layer

摘要

Heterostructures have been grown of YBa sub(2)Cu sub(3)O sub(7)/SrTiO sub(3) deposited on LaAlO sub(3) substrates by PLD. RHEED observations were made during deposition of the ferroelectric layer and the parameters were optimized to produce near 2D growth. After XRD and surface resistance measurements, these samples were then patterned into tunable resonators comprising of interdigital combs. In these structures the tunability is achieved as a result of the change in the dielectric constant of the ferroelectric material between the combs when a DC voltage is applied. In excess of 500 MHz of tuning in the resonant frequency of the device has been observed, and from these data it has been possible to derive values of epsilon sub(r) and tan delta for the ferroelectric layer which can then be used to design and model tunable microwave devices.