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

Ferroelectric properties of SrBi2TaNbO9 (SBTN) thin films were changed in t erms 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/S BTN heterostructure fabricated by r.f. magnetron shuttering method. Excess Bi composition was controlled by changing the thickness of the sandwiched B i2O3 in SBTN/Bi2O3/SBTN heterostructure from 50 Angstrom to 400 Angstrom. A s the thickness of Bi2O3 films were increased from 0 to 100 Angstrom, the g rain grew faster and the ferroelectric properties were im; proved. On the o ther 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 c ase, 2Pr and Ec were 14.75 mu C/cm(2) and 53.4 kV/cm, respectively.