Thickness dependence of characteristics for (Ba, Sr)TiO3 thin films prepared by metalorganic chemical vapor deposition

(Ba-0.6,Sr-0.4)TiO3 thin films were prepared by metalorganic chemical vapor deposition (MOCVD) using bisdipvaloyl-methanatobarium tetraethylenepentami ne adduct (Ba(C11H19O2)(2)(C8H23N5)(2)), bisdipvaloylmethanatostrontium tet raethylene-pentamine adduct (Sr(C11H19O2)(2)(C8H23N5)(2)), and titanium iso propoxide (Ti(i-OC3H7)(4)) as starting materials. The thickness dependence of permittivity and other characteristics were investigated for epitaxially grown barium strontium titanate (BST) thin films on Pt(100)/MgO(100) subst rates and nonepitaxially grown BST films on Pt(111)/MgO(100) substrates. Th e epitaxially grown films had a high relative permittivity (1200) at thickn esses greater than 120 nm. Permittivity decreased with the film thickness w hen the thickness was less than 120 nm, but remained constant at thicknesse s between 50 and 80 nm. The nonepitaxially grown films had a relative permi ttivity of 600 at a thickness greater than 100 nm and decreased with decrea sing film thickness when the thickness was below 100 nm. In this paper, the origin of thickness dependence is discussed in terms of the grain-size eff ect and the strain effect.