Ž . Applied Surface Science 108 1997 385–389 Tetragonal BaTiO thin films hydrothermally grown on TiO 3 2 single crystals V.M. Fuenzalida a, ) , Judit G. Lisoni a , Nilton Itiro Morimoto b , Juan.C. Acquadro b a UniÕersidad de Chile, FCFM, Casilla 487-3, Santiago, Chile b USP, C.P. 66318, SP 05389-970 Sao Paulo, Brazil Received 6 May 1996; accepted 25 August 1996 Abstract Tetragonal BaTiO films were prepared on single crystal TiO substrates by the hydrothermal method. The films were 3 2 Ž . grown in 0.5 M Ba OH aqueous solutions at 1508C and 2008C during 4 h. X-ray diffraction analysis demonstrated the 2 presence of polycrystalline BaTiO in its tetragonal phase, in contrast to hydrothermally grown BaTiO on metallic 3 3 substrates, which usually results in the cubic phase under similar conditions. Rutherford backscattering measurements in the channeling mode showed that the barium ions did not occupy lattice positions and that there is not a sharp film–substrate interface. The diffusion range of the moving species — either Ti or Ba — was about 1 mm, and the diffusion coefficient at 1508C was estimated to be about 10 y16 m 2 s y1 . 1. Introduction Ž .Ž . Perovskite thin films such as Ba, Sr Ti, Zr O 3 have interesting dielectric properties and several methods have been used to prepare them. Recently hydrothermal methods have been used for low-tem- perature preparation of thin films of these materials w x grown on metallic or metal coated substrates 1–3 . Ž . The transition metal Ti, Zr is treated in an alkaline solution, with pH ) 11 at temperatures ranging from wx wx 558C 4 to 6008C 5. After the initial attempts to obtain a variety of films on different substrates, the following questions have been addressed. ) Corresponding author. Tel.: q56-2-6784392; fax: q56-2- 6967359; e-mail: vfuenzal@tamarugo.cec.uchile.cl. Ž. a The use of non-alkali electrolytes was reported w x by Bendale et al. 4,6 . Ž. b Lowering the synthesis temperature below w x 1008C was also investigated 4,6,7 and it is now commonly accepted that cubic BaTiO films can be 3 grown at 558C. Ž. c The electrochemical aspects of the initial growth stages and the influence of electric pulses at the start of the growth process on the film mi- wx crostructure were recently reported 8 . Ž. d Surface properties of these materials have also wx been reported 2 . Hydrothermal BaTiO films normally grow in the 3 cubic phase, which is metastable at room tempera- ture, but stable under the common synthesis condi- tions, since the structural transition temperature is about 1208C. On the other hand, hydrothermal BaTiO powders are normally formed in the tetrago- 3 0169-4332r97r$17.00 Copyright q 1997 Elsevier Science B.V. All rights reserved. Ž . PII S0169-4332 96 00610-1