Nanoscale imaging of grain orientations and ferroelectric domains in (Bi1−xLax)4Ti3O12 films for ferroelectric memories

Abstract

We report results of nanoscopic investigation of grain crystallographic orientations and ferroelectric domains by electron backscatter diffraction (EBSD) technique and piezoresponse force microscope (PFM), respectively, in (Bi1−xLax)4Ti3O12 (BLT) films for ferroelectric semiconductor memories. It is demonstrated that the EBSD technique is useful in characterizing nanoscale grain crystallographic orientations of BLT films. Comparison studies of grain orientations by EBSD technique and switching properties of ferroelectric domains by PFM show that c-axis parallel to normal oriented grains with almost linear dielectric properties have platelike morphology. However, a- or b-axis oriented grains with superior ferroelectric properties have ellipsoidal morphology with a size of less than 0.2μm in long axis. Consequently, the suppression of the platelike structures through process controls is important for the realization of high-density BLT-based memories.