Growth and Characterization of BaxSr1-xTiO3 Thin Films Derived by A Low-Temperature Process Jinbao Xu, Jiwei Zhai,* and Xi Yao Functional Materials Research Laboratory, Tongji UniVersity, Shanghai 200092, China
CRYSTAL GROWTH & DESIGN 2006 VOL. 6, NO. 10 2197-2199
ReceiVed March 31, 2006; ReVised Manuscript ReceiVed August 22, 2006
ABSTRACT: The BaxSr1-xTiO3(BST) ferroelectric thin films on Pt(111)/Ti/SiO2/Si(100) substrates were fabricated by a sol-gel/hydrothermal process at a very low-temperature processing of 100-200 °C. X-ray diffraction analysis showed that the BST thin films on Pt(111)/Ti/ SiO2/Si(100) substrates were polycrystalline with a (110) preferential orientation. A dielectric constant at 1 MHz and a dissipation factor dependence of frequency in the range of 100-10 MHz for the Au/BST/Pt capacitors were obtained. Ferroelectric thin films (PbTiO3(PTO), Pb(Zr,Ti)O3(PZT), BaTiO3(BTO), and BaxSr1-xTiO3(BST)) with a perovskite structure have offered tantalizing potential for engineering applications since their discovery. In particular, their switchable electric polarization (spontaneous polarization, Ps) is ideal for use in devices for nonvolatile memory. Many thin film deposition techniques have been developed to prepare ferroelectric thin films, including pulsed laser deposition,1 metal-organic chemical vapor deposition,2 sputtering,3 metalorganic deposition,4 and sol-gel.5 However, all these techniques require a high processing temperature (500 °C or above) for crystallization, which inevitably results in undesirable interdiffusion and inteaction between thin films and substrates. Such interdiffusion degrades properties of the films and hinders the integration with a Si-based readout integrated circuit (ROIC).6-10 Many efforts have been made to fabricate ferroelectric film at low temperatures. Song et al.11 have used a modified sol-gel technique to prepare (110)-oriented PZT film at temperatures as low as 550 °C on a Pt/Ti/SiO2/Si substrate. Tsai et al.12 reported the dielectric properties of BST films prepared by rf sputtering at 450 °C. Jung et al.13 used hydrothermal epitaxy to fabricate a heteroepitaxial PbTiO3 (PTO) thin film on a Nb-doped (001) cubic SrTiO3 (NSTO) substrate at 160 °C. It is well-known that hydrothermal epitaxy is a technique that utilizes aqueous chemical reactions to synthesize inorganic materials under elevated pressure (
