Epitaxial growth of (001)-oriented Ba 0.5 Sr 0.5 TiO 3 thin films on a -plane sapphire with an MgO/ZnO bridge layer

High quality (001)-oriented Ba 0.5 Sr 0.5 TiO 3 (BST) thin films have been grown on a -plane sapphire ( 11 2 ¯ 0 ) by rf magnetron sputtering using a double bridge layer consisting of (0001)-oriented ZnO (50 nm) and (001)-oriented MgO (10 nm) prepared by plasma-assisted molecular beam epitaxy. X-ray diffraction revealed the formation of three sets of in-plane BST domains, offset from one another by 30°, which is consistent with the in-plane symmetry of the MgO layer observed by in situ reflective high electron energy diffraction. The in-plane epitaxial relationship of BST, MgO, and ZnO has been determined to be BST [110]//MgO [110]//ZnO [ 11 2 ¯ 0 ] and BST [110]/MgO [110]//ZnO [ 1 1 ¯ 00 ] . Capacitance-voltage measurements performed on BST coplanar interdigitated capacitor structures revealed a high dielectric tunability of up to 84% at 1 MHz.