In situ fabrication of SrTiO 3–BaTiO 3 layered thin films by hydrothermal-electrochemical technique

Abstract

Layered thin films in the BaTiO 3–SrTiO 3 system have been fabricated by a hydrothermal-electrochemical method either in a closed autoclave or in a flow system using the titanium substrate and Ba- and Sr-hydroxides or acetates as sources of titanium, barium, and strontium, respectively. The synthesis conditions (temperature in the range of 120–200°C, current density of 1–20 mA/cm 2, flow rates of 1–50 cm 3/min, duration of 1–24 h) allowed an easy control of the microstructure of the titanate layers. BaTiO 3 layers could be deposited easily on SrTiO 3 layers at 150°C (1 h, 1 mA/cm 2) both in the closed autoclave and in the flowing solution. To deposit SrTiO 3 layers on BaTiO 3 layers, a current density of 10 mA/cm 2 or preceding water leaching of the BaTiO 3 surface were necessary. The multilayered nature of the BaTiO 3–SrTiO 3 films have been revealed by XRD, AFM, and XPS at various stages of their preparation. Based upon the experimental results, a growth mechanism of the BaTiO 3–SrTiO 3 double layers has been proposed.