Ferroelectric properties of La and Zr substituted Bi_(4)Ti_(3)O_(12) thin films

摘要

Thin films of A-site substituted, B-site substituted, and both A- and B-sites cosubstituted Bi_(4)Ti_(3)O_(12) (BTO) by La~(3+) and Zr~(4+), i.e., Bi_(3.25)La_(0.75)Ti_(3)O_(12) (BLT), Bi_(4)Ti_(2.8)Zr_(0.2)O_(12) (BTZ), and Bi_(3.25)La_(0.75)Ti_(2.8)Zr_(0.2)O_(12) (BLTZ), were fabricated on Pt/Ti/SiO_(2)/Si substrates by pulsed laser deposition. Structures of the films are investigated by x-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Compared to the well known BLT films, both the BTZ and BLTZ films have larger remanent polarization (P_(r)) but smaller coercive field (E_(c)). It is shown experimentally that the oxygen vacancy is the predominant factor determining ferroelectric fatigue. The effects of substitution on structural and ferroelectric properties of BTO are discussed in detail. As a result, the A- and B-sites cosubstitution might be one of the promising ways to improve ferroelectric properties of BTO.