Structural and Electric Characteristics of Two-Layer Bi4Ti3O12/(Ba,Sr)TiO3 Thin Films Deposited on a Silicon Substrate by Radio-Frequency Sputtering at Increased Oxygen Pressures

Abstract

The 400–450-nm-thick Bi4Ti3O12 thin films with various orientations of crystallites with respect to a normal to the (100)Si substrate plane have been studied. It is established that the crystallite orientation can be controlled by varying the composition of the 4-nm-thick BaxSr1 – xTiO3 sublayer. The use of Ba0.4Sr0.6TiO3 as a sublayer leads to the growth of the Bi4Ti3O12 film in the single-crystal state with plane (001) parallel to the substrate plane and with a monoclinic distortion of the crystal structure. The Ba0.8Sr0.2TiO3 sublayer is shown to lead to the formation of four crystallite orientations: (111), (117), (100), and (110) and two groups of domains in the Bi4Ti3O12 film; the first group with the polarization direction p-erpendicularly to the substrate and the second group with the polarization directed in the angular range 45.2°–57° with respect to a normal to the substrate. It is shown that, in the Bi4Ti3O12 film with the Ba0.8Sr0.2TiO3 sublayer, the polarization is directed to the substrate and is switched to new stable state with the polarization direction from the substrate when applying an external voltage higher than a critical one (4 V).