Rapid synthesis and scanning probe analysis of BaxSr1-xTiO3 composition spread films on a temperature gradient Si(100) substrate

We have succeeded in rapid optimization of dielectric properties in a combinatorial BaxSr1-xTiO3 film library fabricated on a highly insulating Si substrate. The thin-film library was prepared by using a pulsed-laser molecular beam epitaxy system equipped with a combinatorial mask for controlling compositional (i.e. x in BaxSr1-xTiO3) variations and a temperature-gradient sample holder for obtaining a growth temperature variation along the x and y axis of the substrate, respectively. The dielectric properties of this combinatorial library were mapped by a scanning evanescent microwave probe at a frequency of 2.5 GHz, revealing a strong dependence of permittivity and loss on the composition and on the growth temperature. The optimum permittivity was found in the film with x similar to 0.5 grown at 730 C. From X-ray diffraction analysis, strong correlation was found between the grain orientations and dielectric properties.