Epitaxial Regrowth of Ferroelectric Thin Films on Bottom Electrodes

Abstract

The practical use of ferroelectric thin films in devices such as FeRAM requires a capacitance-like geometry and then a bottom electrode. Platinum is proposed based on its resistance to oxidation and unit-cell constants fitting quite closely the ones of typical substrates and ferroelectric materials: indeed, high quality, smooth epitaxial Pt layers with various orientations, namely (100), (110) and (111), were reproducibly obtained. Various examples of the epitaxial regrowth on such sublayers of ferroelectrics are shown, in the case of SrBi₂Nb₂O₉ (SBN) and KTa_{1− x} Nb _x O₃ (KTN). The observed orientations are compared to the ones obtained on bare bulk oxide substrates and oxide sublayers and discussed in terms of interface anchoring (Near Coincidence Site Lattice model), explaining the orientational competition frequently encountered in such metal-oxide heterostructures.

Keywords:

• Thin films
• ferroelectrics
• epitaxy
• electrodes

PACS codes:

• 77.55.+f
• 77.84.−s
• 68.55.−a
• 81.15.Aa
• 84.40.Lj

Acknowledgments

This work has been supported in part by a CNRS-Région Bretagne grant and by CNRS under “Materials Program.” XRD equipment has been purchased with the financial support of the French Research Ministry, the Région Bretagne, Département d'Ille-et-Vilaine and Rennes Métropole (PPF, CPER 1999–2006). SEM observations have been carried out in CMEBA (Rennes University center for scanning electron microscopy and microanalysis).