Microstructure and properties of Mn- or Nb-doped Bi4Ti3O12 thin films by chemical solution deposition

Abstract

Bismuth titanate (Bi4Ti3O12) has a layered perovskite structure and exhibits strong anisotropic physical properties. Orientation control is important for the Bi4Ti3O12 thin films to apply to various electronic devices. In this study, we investigate the effects of Mn- or Nb-doping on the microstructure and properties of Bi4Ti3O12 thin films. Mn-doped or Nb-doped Bi4Ti3O12 thin films were fabricated by chemical solution deposition. The spin-coated films were fired at 800°C for lmin and successively annealed at 700°C for 1 hour in oxygen gas. The surface morphology of the deposited films varied with Mn- or Nb-doping. The surface of the non-doped Bi4Ti3O12 films consisted of plate-like grains. Mn- or Nb-doping suppressed grain growth. Non-doped Bi4Ti3O12 films showed c-axis orientation, while Mn- or Nb-doped films showed mixed c-axis and (117) orientation. Remanent polarization (Pr) and the coercive field (Ec) of the non-doped Bi4Ti3O12 films on Pt/Ti/SiO2/Si were 1.3μC/cm2 and, while 1 mol% Mn-doped Bi4Ti3O12 films exhibited a Pr of 2.2 μC/cm2. Mn-doping decreased leakage current. Nb-doping increased permittivity and remanent polarization, but also increased leakage current.