Frequency dependent ferroelectric and electrical properties of (Ho, Ni) co-doped BiFeO3 thin films

We have evaluated the ferroelectric and electrical properties of pure BiFeO3 (BFO) and (Bi0.9Ho0.1)(Fe1−xNix)O3−δ (BHFNxO, x = 0.01, 0.02, and 0.03) thin films as frequency varying from 1 to 50 kHz on Pt(111)/Ti/SiO2/Si(100) substrates by using a chemical solution deposition method. With the frequency from 1 to 10 kHz, the decrease of remnant polarization (2Pr) of the BHFN0.02O thin film was about 27 %, from 26 to 19 μC/cm2, which is one half lower than those of the BHFNxO (x = 0.01 and 0.03) thin films. Otherwise, the variation of the coercive electric field (2Ec) was relatively small, which were 16, 11 and 3 % for the BHFNxO (x = 0.01, 0.02, and 0.03) thin films. The remnant polarization (2Pr) and the coercive electric field (2Ec) values of the BHFN0.02O thin film show the dependence of measurement frequency and it has been fairly saturated about 30 kHz. Also, the leakage current density of the co-doped BHFN0.02O thin film showed three orders lower than that of the pure BFO, 2.14 × 10−6 Å/cm2 at 100 kV/cm.