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SYFS: Nichtflüchtige Festkörperspeicher

SYFS 4: Poster

SYFS 4.1: Poster

Samstag, 5. März 2005, 08:30–16:30, Poster TU C

Reduction of azimuthal domains in (100)- and (118)-oriented ferroelectric Bi_3.25La_0.75Ti₃O_{1 2} films making use of YSZ and Si substrates with definite off-cut — •Sung Kyun Lee¹, Ho Nyung Lee², and Dietrich Hesse¹ — ¹Max-Planck-Institut für Mikrostrukturphysik, D-06120 Halle (Saale), Germany — ²Condensed Matter Science Division, Oak Ridge National Laboratory, TN 37831, USA

La-substituted bismuth titanate is a candidate for non-volatile ferroelectric RAMs, combining a high remanent polarization Pr with a very good fatigue resistance. Uniformly oriented Bi_3.25La_0.75Ti₃O_{1 2} (BLT) films have been grown by pulsed laser deposition. a-axis oriented BLT films on SrRuO₃(110)- electroded, YSZ(100)-buffered Si(100) wafers show a Pr of 32 microCoulomb/sqr-cm and a small fatigue of less than 10 percent after a billion cycles. Since (110)-oriented SrRuO₃ electrode layers grow on YSZ(100) buffer layers with four azimuthal domains, the BLT films consist of eight azimuthal domains involving 20^∘-, 70^∘- and 90^∘-domain boundaries. To reduce the number of azimuthal domains, SrRuO₃ layers and BLT films were grown by PLD onto YSZ(100) and YSZ(100)-buffered Si(100) single crystal substrates having a definite off-cut. The offcut angle was varied from zero to 5^∘ in steps of 1...2^∘; two azimuthal offcut directions were used, viz. [100] and [110]. The films were investigated by XRD pole figures and Phi scans, TEM, and ferro-electric measurements. A [110] offcut allowed to effectively reduce the number of domains and domain boundaries by 50 percent.