Ion Modification for Improvement of Insulating and Ferroelectric Properties of BiFeO₃ Thin Films Fabricated by Chemical Solution Deposition

Abstract

Ion modification techniques for improving the insulating and ferroelectric properties of BiFeO 3 (BFO) thin films are reported. Rare-earth-substituted BFO films with chemical compositions of Bi 1:00Àx RE x Fe 1:00 O 3 [RE = La and Nd] were fabricated on (111)Pt/TiO 2 /SiO 2 /(100)Si substrates using a chemical solution deposition technique. Well-saturated P-E curves were obtained for La 3þ -and Nd 3þ -substituted BFO films, while the curve of a nonsubstituted BFO film was distorted due to the leakage current. Remanent polarization (P r ) values measured at 10 K were respectively 44 and 51 mC/cm 2 , for La 3þ -and Nd 3þ -substituted BFO films, which are significantly superior to conventional Pb-free ferroelectrics.

Structural evolution and physical properties of Bi1−xGdxFeO3 ceramics

“…The antiferromagnetic spin configuration of BFO can be modified by superimposing a spiral modulated spin structure (SMSS, 620 Å periodicity) [8], which counteracts the macroscopic magnetization and prohibits the linear magnetoelectric effect from being observed. Chemical doping of BFO can not only tune the electric conductivity [9][10][11] but also suppress the spiral spin structure to make the macroscopic magnetization observable [12,13]. Since the ferroelectric distortion of BFO mainly results from a hybridization of the Bi 6s lone-pair electrons with the s/p orbits of O [14], a substitution of rare earth element (RE) for Bi would weaken the hybridization and affect the ligand field at the Fe ions.…”

Study of electric and magnetic properties of (Bi0.9Pb0.1) (Fe0.9Ti0.1)O3 nanomultiferroic system

“…However, a small polarization has been observed in bulk BFO single crystal 10 and BFO bulk ceramics, 11 and their hysteresis loops were not saturated, which were attributed to the high level of leakage due to charge defects and nonstoichiometry. 12 To overcome these leakage problems ion substitution 13,14 or solid solution with other perovskite materials 15,16 has been tried, and wellsaturated hysteresis loop with remanent polarization has recently been reported in single phase BiFeO 3 ceramics. 17,18 Stoichiometric BFO has a G type AF structure 19 and has residual magnetic moment due to the canting of magnetic moments arising from oxygen vacancies.…”

Leakage Current Properties of Cation-Substituted BiFeO3 Ceramics

“…Sintering conditions were optimized to obtain densified BFO ceramics at temperatures as low as 8,17,18,24) , as can be seen in Fig.1.…”

“…One is a procedure for directly lowering the number of the oxygen vacancies by the injection of oxide ions 16) and doping of rare-earth cations to the Bi 3+ -sites. 8,[17][18][19][20] The other method is to compensate the unbalanced ionic charge induced by the formation of oxygen vacancies. Thus cation substitution with higher valences for the Fe 3+ -sites in BFO has been studied.…”