Preparation and Basic Properties of Ferroelectric Bi₃TiNbO₉—Bi₄Ti₃O₁₂ Thin Films with Different Superlattice Structures

Abstract

Natural-superlattice-structured Bi₃TiNbO₉–Bi₄Ti₃O₁₂ (m = 2–3) (BTN–BIT) thin films have been grown on Pt/TiO₂/SiO₂/Si substrates at 400°C to 550°C by pulsed laser deposition (PLD) using a BTN–BIT (1 mol:1 mol) target. BTN–BIT film prepared at 550°C and 0.07 Torr has single phase whose c lattice parameter is estimated to 8.300 nm in consideration of periodicity of lattice structure. This lattice constant is very close to the value (8.316 nm) of that of two unit cells of BTN and one unit cell of BIT, which is 2-1 superlattice structure of BTN–BIT. The lattice constant (2.905 nm) of post-annealed BTN–BIT film prepared at 400°C is very close to the value (2.900 nm) of that of half unit cell of BTN and half unit cell of BIT, which is 1–1 superlattice structure of BTN–BIT. The BTN-BIT film with 2–1 superlattice structure has large remanent polarization (2P_r= 50 μ C/cm²) due to the structural deformation through Bi₂O₂ layer.

Keywords:

• Bi₃TiNbO₉
• Bi₄Ti₃O₁₂
• BLSFs
• superlattice
• remanent polarization