A new MOD method to prepare Sr_0.7Bi_2.2Ta_2O_9 ferroelectric films for non-volatile RAM memories

摘要

Strontium bismuth tantalite, Sr_0.7Bi_2.2Ta_2O_9 (SBT), thin films were prepared by a new metalorganic decomposition (MOD) method using strontium (2,2,6,6-tetramethyl-3,5-heptanedionate), and tantalum ethoxide as the metalorganic precursors. Films with a thickness of 300 nm wer prepared on Si(100) with a layered bottom electrode (Pt/TiO_2SiO_2). After crystallization in oxygen for 60 min at 750 deg C, single orthorhombic-phased films were obtained as determined by XRD, but no preferred crystalline orientation was revealed using this technique. Characterization by AFM showed that the polycrystalline films were densely packed and crackfree, and had an average surface roughness (rms) of 8 nm and a mean grain size of 150 nm. The remnant polarization and coercive field were 6μC cm~-2 and 74 kV cm~-1, respectively. The SBT films showed a very low polarization fatigue after 10~11 switching cycles and good retention properties.