In situ fabrication of SrTiO_3-BaTiO_3 layered thin films by hydrothermal-electrochemical technique

摘要

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 deg C, current density of 1-20 mA/cm~2, flow rates of 1-50 cm~3/min, duration of 1-24h) allowed an easy control of the microstructure of the titanate layers. BaTIO_3 layers could be deposited easily on SrTIO_3 layers at 150 deg C (1h, 1mA/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 10mA/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.