Films of Ba0.5Sr0.5TiO3 were grown heteroepitaxially onto (001) MgO substrates by

pulsed laser deposition to fabricate microwave phase shifters for the frequency

range: 45MHz to 50GHz. Both as-grown and ex situ annealed films had a cube-oncube

epitaxial relationship with <100> Ba0.5Sr0.5TiO3ǁ<100>MgO. Threading

dislocations were the predominant defects, mostly with Burgers vectors b = <101>.

Growth at 10-1 mbar oxygen pressure, compared to 10-4mbar, resulted in

significantly better properties. Ex situ annealing of the film grown at 0.1mbar

resulted in a reduction of 40% in threading dislocation density and a 40% increase

in dielectric tunability.

Effect of Growth Defects on Microwave Properties in Epitaxial Ba0.5Sr0.5TiO3 Thin

Films Grown on (001) MgO by Pulsed Laser Deposition. Y.Y.Tse, P.M.Suherman,

T.J.Jackson, I.P.Jones: Philosophical Magazine, 2008, 88[16], 2505-18