YBa₂Cu₃O_7-x/SrTiO₃//LaAlO₃ heterostructures obtained by injection MOCVD

Abstract

YBa₂Cu₃O_7-x /Ba_xSr_1-xTiO₃ /LaAlO₃ heterostructures can be used as a basis for devices with voltage control in microwave circuits.

Ba_xSr_1-xTiO₃ (x=0–0.1) (BST) thin films have been epitaxially grown on LaAlO₃ substrates using injection MOCVD. The excellent crystalline quality of the obtained BST films can be proven by a FWHM of <0,2° for the rocking curve of the (002) BST reflection. An AFM study revealed flat surfaces, showing a surface roughness R_s as low as 1nm. YBa₂Cu₃O_7-x/Ba_xSr_1-x TiO₃//LaAlO₃ heterostructures were than optimised. The YBa₂Cu₃O_7-x (YBCO) layers obtained on Ba_xSr_1-xTiO₃ films are epitaxial with a FWHM of 0.45° for the (005) YBCO rocking curve and display very promising superconducting properties of T_c=92K.

Finally the microwave properties of the superconducting films were studied. For YBa₂Cu₃O_7-x layers directly deposited on LaAlO₃, surface resistance values of 0,32mΩ were obtained, while for YBa₂Cu₃O_7-x /SrTiO₃//LaAlO₃ heterostructures, higher values of 1mΩ at 8.5GHz were measured.

Key Words:

• Injection MOCVD
• Films
• Ba_xSr_1-xTiO₃
• Oxide Superconductors
• X-ray
• Electrical Properties