BiFeO3 Thin Films Prepared by ALD

Bismuth ferrite (BiFeO₃) is one of the most technologically promising multiferroics with a simple perovskite structure and high ferroelectric and antiferromagnetic ordering temperatures. High-quality heteroepitaxial growth of BiFeO₃ thin films has been demonstrated mainly by PLD, MBE, RF sputtering and MOCVD, almost of them requiring ultrahigh vacuum and thus are rather expensive, particularly when used on an industrial scale. In contrast, ALD is relatively inexpensive and can produce atomically smooth coverage on structures with extremely high aspect ratio. In this talk we will discuss the growth of BiFeO₃ thin films by ALD and the influence of the growth parameters on the phase composition of the resulting films. Briefly, the amorphous films were first grown and analyzed on Si wafers, SrTiO₃(001), Nb:SrTiO₃(001) at 250 C. Next, ex situ annealing was performed at various temperatures to study the crystallization process. According to XRD analysis and TEM imaging, the ALD-grown BiFeO₃ films demonstrated a high crystallinity and epitaxial quality. Piezoresponse force microscopy showed an expected response of the ferroelectric phase. The ALD growth of BiFeO₃ will provide a new way of convenient, technologically-oriented and commercially realizable deposition of a promising multiferroic for nanoelectronic devices.

This work was supported by the NSF DMR under 1124696 and by the ARO under W911.