Effect of film composition on the orientation of (Ba,Sr)TiO3 grains in (Ba,Sr)(y)TiO(2+y) thin films

Thin films of composition (Ba,Sr)(y)TiO(2+y), with y in the range 0.43-1.64, were deposited by MOCVD on (100) MgO substrates at various growth conditions. XRD and TEM studies showed that the films were composed of epitaxial Ba(1-x)Sr(x)TiO3 (x approximately equal to 0.06) grains and an amorphous phase. The orientation of the tetragonal Ba(1-x),Sr(x)TiO3 grains (pure a axis, pure c axis, or a mix of the two) was found to be strongly dependent upon film composition. This composition dependence is explained for the majority of the Ti-rich films by an analysis of average strains in the two-phase films, assuming a compressive strain of approximately equal to 1 percent in the amorphous phase. (Author)