Improvement of ferroelectric properties by heat treating SrBi2(Ta1-xNbx)(2)O-9/Bi2O3/SrBi2(Ta1-xNbx)(2)O-9 heterostructure

Abstract

Ferroelectric properties of SrBi2TaNbO9 (SBTN) thin films were changed in terms of the amount of Bi content in SBTN. We suggested that the addition of excess Bi in the films could be accomplished by heat treating SBTN/Bi2O3/SBTN heterostructure fabricated by r.f. magnetron shuttering method. Excess Bi composition was controlled by changing the thickness of the sandwiched Bi2O3 in SBTN/Bi2O3/SBTN heterostructure from 50 Angstrom to 400 Angstrom. As the thickness of Bi2O3 films were increased from 0 to 100 Angstrom, the grain grew faster and the ferroelectric properties were im; proved. On the other hand, when the thickness of Bi2O3 films was greater than 400 Angstrom, a Bi2Pt phase appeared as a second phase, which led to poor ferroelectric properties. The maximum remanent polarization (2Pr) and good coercive field (Ec) were obtained for the SBTN/Bi2O3 (100 Angstrom)/SBTN films. In this case, 2Pr and Ec were 14.75 mu C/cm(2) and 53.4 kV/cm, respectively.