A new MOD method to prepare Sr0.7Bi2.2Ta2O9 ferroelectric films for non-volatile RAM memories

Strontium bismuth tantalate, ST0.7Bi2.2Ta2O9 (SBT), thin films were prepare d by a new metalorganic decomposition (MOD) method using strontium (2,2,6,6 -tetramethyl-3,5-heptanedionate) bismuth (2,2,6,6-tetramethyl-3,5-heptanedi onate), and tantalum ethoxide as the metalorganic precursors. Films with a thickness of 300 nm were prepared on Si(100) with a layered bottom electrod e (Pt/TiO2/SiO2). After crystallization in oxygen for 60 min at 750 degrees C, single orthorhombic-phased films were obtained as determined by XRD, bu t no preferred crystalline orientation was revealed using this technique. C haracterization by AFM showed that the polycrystalline films were densely p acked 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 w ere 6 mu C cm(-2) and 74 kV cm(-1), respectively. The SBT films showed a ve ry low polarization fatigue after 10(11) switching cycles and good retentio n properties. (C) 2000 Elsevier Science Ltd. All rights reserved.