YBa2Cu3O7-x /SrTiO3//LaAlO3 heterostructures obtained by injection MOCVD

YBa2Cu3O7-x /BaxSr1-xTiO3/LaAlO3 heterostructures can be used as a basis fo r devices with voltage control in microwave circuits. BaxSr1-xTiO3 (x=0-0.1)(BST) thin films have been epitaxially grown on LaAlO 3 substrates using injection MOCVD. The excellent crystalline quality of th e obtained BST films can be proven by a FWHM of <0,2<degrees> for the rocki ng curve of the (002) BST reflection. An AFM study revealed flat surfaces, showing a surface roughness R-s as low as 1nm. YBa2Cu3O7-x/BaxSr1-x TiO3/La AlO3 heterostructures were than optimised. The YBa2Cu3O7-x (YBCO) layers ob tained on BaSr1-xTiO3 Alms are epitaxial with a FWHM of 0.45 degrees for th e (005) YBCO rocking curve and display very promising superconducting prope r ties of T-c=92K. Finally the microwave properties of the superconducting films were studied. For YBa2Cu3O7-x layers directly deposited on LaAlO3. surface resistance va lues of 0,32m Omega were obtained, while for YBa2Cu3O7-x/SrTiO3/LaAlO3 hete rostructures, higher values of 1m Omega at 8.5GHz were measured.