Mild hydrothermal synthesis of titanate films: From polycrystalline BaTiO₃ to epitaxial PbTiO₃

Abstract

Titanate films, a technological important dielectric, have found significant applications ranging from materials science to ferroelectronics. A vacuum-intensive method is traditionally employed to fabricate these films, but it is condition stringent and so relatively expensive, while a high-temperature process is needed for crystallization during or after film formation, which may be incompatible with the underlying monolithic circuits. Fortunately, the hydrothermal method, which was a traditional way for producing ceramic micropowders, has now been newly developed as a non-traditional way and is increasingly being used to prepare perovskite oxide films. Here we report that films of two classic examples of ferroelectric perovskites, BaTiO₃ and PbTiO₃, can be formed under mild hydrothermal conditions of temperatures lower than 200°C and pressures lower than 1.0 MPa. The BaTiO₃ films formed on Ti-coated Si substrates are well crystallized submicrocrystallites. A better understanding of the growth mechanisms of these films suggests a possible route to hydrothermal epitaxy of PbTiO₃ on SrTiO₃. As the result, our trials on SrTiO₃(100) substrates proved that an epitaxial film of PbTiO₃ was successfully obtained.