NT2: Oxide and Chalcogenide-Based Thin Films and Nanostructures for Electronics and Energy Applications

Martin Frank, IBM T.J. Watson Research Center

Epitaxial BaTiO₃ on Silicon and Silicon Germanium: Nanoscale Characterization, Ferroelectricity and Integration into TiN-Gated Devices

Written by Michael Lee

Researchers at IBM believe the pathway toward developing field-effect ferroelectric BaTiO₃ (BTO) microelectronics begins with integration into current silicon process lines. The critical challenge lies with controlling the heterointerface between BTO and Si as the two materials have different bonding types, lattice parameters, and thermal expansion coefficients. Additionally, growing an oxide on silicon is further complicated by the tendency for native oxide formation. Carefully tuned surface passivation and molecular beam epitaxy provides high quality films with an out-of-plane polarization vector—the first step toward device fabrication. Ultimately researchers were unable to fabricate an epitaxial BTO capacitor with a TiN top electrode, but surprisingly did observe the desired behavior in the (quasi)-amorphous nanocrystalline BTO film that emerged. Other tests verified the effect was not ionic motion, thus demonstrating the first ferroelectric, gated device, and one that may eliminate concerns surrounding grain boundary effects.