Self-patterning nano-electrodes on ferroelectric thin films for gigabit memory applications

In the present work, we report self-assembling bismuth-containing nano-electroded cells of layered perovskite ferroelectric thin films that are about 200 nm in size, that is 50 times smaller than the smallest cell reported to date. Heteroepitaxial Bi-rich ${\mathrm{Bi}}_{\mathrm{4}}{\mathrm{Ti}}_{\mathrm{3}}{\mathrm{O}}_{\mathrm{12}}$ films were grown by pulsed laser deposition (PLD) on top of epitaxial conductive ${\mathrm{La}}_{\mathrm{0.5}}{\mathrm{Sr}}_{\mathrm{0.5}}{\mathrm{CoO}}_{\mathrm{3}}$ (LSCO) layers equally deposited by PLD. The epitaxial LSCO has been grown on top of an epitaxial ${\mathrm{CeO}}_{\mathrm{2}}$ yttrium-stabilized zirconia (YSZ) stack, itself deposited by PLD on Si(100) substrates. As a consequence of the high substrate temperature during the epitaxial deposition of the ${\mathrm{Bi}}_{\mathrm{4}}{\mathrm{Ti}}_{\mathrm{3}}{\mathrm{O}}_{\mathrm{12}}$ layer, the excess Bi segregates, migrates to the surface where it forms a self-organized array of epitaxial mesas which possess metallic-like electrical characteristics.