Growth of YBa2Cu3O7-x/BaxSr1-xTiO3/LaAlO3 heterostructures by injection MOCVD for microwave applications

It is well known that including dielectrics in layered structures such as Y Ba2Cu3O7-x/BaxSr1-xTiO3/LaAlO3 could be used as a basis for devices with vo ltage control of microwave circuit parameters. In this study BaxSr1-xTiO3 ( BST) (x=0 to 1) thin films have been epitaxially gr own on LaAlO3 at a subs trate temperature of 800 degrees C using a new liquid source delivery techn ique called injection MOCVD. This process, based on computer-controlled inj ection of micro-amounts of liquid droplets, gives rise to BST thin films wi th their (100) orientation perpendicular to the substrate displaying a FWHM of as low as 0.14 degrees for the 002 diffraction omega scan. AFM studies of the films, surface morphology revealed a smooth surface. In a next step dielectric properties are discussed Finally, the possibility of obtaining Y Ba2Cu3O7-x/BaxSr1-xTiO3/LaAlO3 heterostructures was investigated resulting in quite promising values for the critical temperature T-c of 88 K for the YBCO films. (C) 1999 Published by Elsevier Science Limited. All rights rese rved.