Decoupling the synergic kinetics of depolarization in ferroelectric Pd-doped bismuth ferrite photoactive thin films

We successfully prepare BiFe_(1-x)Pd_xO₃ (BFP_xO) thin films (i.e. ferroelectric bismuth ferrite with Fe-site partially substituted by palladium ions) as well as BFP_xO/NiO heterostructure though sol-gel method. We try to figure out the two aspects of problems in this work. On one hand, crucial roles that Pd doping plays in optoelectronic characteristics of BFP_xO are elucidated. The relationships among Pd valence, lattice distortion and optoelectronic performance of BFP_xO are built. We confirm that Pd doping can minimize the response time constant of BiFe_(1-x)Pd_xO₃ below 10 ms; meanwhile, the detectivity of BFPO/NiO heterostructure can reach up to ca. 10⁹ Jones. On the other hand, open-circuit voltage decay (OCVD), a kind of transient measurement technique, is adopted to gain an insight into distinct decay stages existing in BFP_xO. The abnormal transient phenomenon with ‘overlong’ relaxation time higher than 10 s is probably contributed by depolarization process of BFP_xO. Consequently, we reveal hidden photoactive natures of ferroic perovskite oxides, which may derive from the synergic kinetics of polarization/depolarization associating to ferroelectric domains and particularly be triggered by the noble metal element doping.