Thermal Annealing and Temperature Dependence of Ferroelectric Properties of CaBi₄Ti₄O₁₅ Thin Films

Abstract

To successfully synthesize CaBi₄Ti₄O₁₅(CBT) thin films, pre-sintered CBT targets were sputtered at room temperature in pure argon on (111)Pt/Si substrates using r.f. magnetron sputtering, followed by annealing at temperatures from 600^oC to 750^oC.The CBT films annealed at 600^oC, 650^oC and 700^oC exhibited well established ferroelectric hysteresis loops. Remanant polarization (P_r), coercive field (E_c), dielectric permittivity and dielectric loss all decrease with decreasing temperature at below 700^oC, while too high an annealing temperature led to excessive bismuth loss. An P_r of 5.09μC/cm² and E_c of 48.0kV/cm were measured at 9V for the CBT film annealed at 700^oC, with a dielectric permittivity and dielectric loss of 413 and 0.75, respectively. Both P_r and E_c increase from room temperature to 120^oC, where an P_r of 6.10μC/cm² and E_c of 58.0 kV/cm were measured at 9V. The observed ferroelectric behaviors of CBT films are discussed and correlated to their microstructural features.