FATIGUE-FREE SRBI2(TAXNB1-X)(2)O-9 FERROELECTRIC THIN-FILMS

Fatigue free ferroelectric thin films of layer-structured SrBi2(TaxNb1 -x)(2)O-9 (0 < x < 1) (SBTN) have been processed, for the first time, using the metallorganic decomposition (MOD) technique. The precursors for the MOD process were synthesized by using Sr(C7H15COO)(2), Bi(C7H1 5COO)(3), Ta(OC2H5)(5), Nb(OC2H5)(5), and (C7H15COOH) as starting mate rials. Films of various compositions were spin coated onto Si-SiO2-Ti- Pt and sapphire substrates. The films were pyrolyzed at different temp eratures and characterized for their phase, composition, microstructur e and ferroelectric properties. The deposited films were of high quali ty and found to exhibit excellent ferroelectric properties; typically, at an applied voltage of 5 V, SET films showed 2P(r) values greater t han 20 mu C cm(-2), dielectric constant around 300 and a coercive held E(c) less than 60 kV cm(-1). The films showed a very low fatigue rate up to 10(9) cycles and a leakage current density of less than 2 x 10( -8) A cm(-2) at 167 kV cm(-1). These results compare well with earlier reports (S.B. Desu and D.P. Vijay, Mater. Sci. Eng. B, 32 (1995) 75) on the ferroelectric properties of laser ablated SBTN thin films. In a ddition, the P-r and E(c) values obtained on laser ablated and MOD der ived SBTN thin films are similar. However, a significant difference ca n be noticed in the value of the measured leakage current densities; M OD derived films exhibit current densities at least an order of magnit ude lower than the laser ablated films. Since the MOD technique is ame nable to large scale production, the results of this study bear signif icant technological implication for the commercial development of fati gue free nonvolatile random access memories.