Aging‐Induced Double Ferroelectric Hysteresis Loops and Asymmetric Coercivity in As‐Deposited BiFe_0.95Zn_0.05O₃ Thin Film

Abstract

The BiFe0.95Zn0.05O3 (BFZO) thin film was fabricated on indium tin oxide/glass substrate using a metal organic decomposition method combined with sequential layer annealing. Double ferroelectric hysteresis loops were observed in the as‐deposited film, indicating that the film is partially aged. This aging phenomenon can be attributed to the formation of defect complexes between oxygen vacancies and acceptors of in the film. The nonreversible transition from double ferroelectric hysteresis loop to the single one can occur during the course of increasing the applied electric field. More importantly, an asymmetry of the coercive field can be found to be strongly dependent on the magnitude and frequency of the electric field. This phenomenon was discussed based on the asymmetric driving force for domain backswitching in BFZO film with a preferential polarization.

Enhanced ferro- and piezoelectric properties of a sol–gel derived BiFe0.95Mn0.05O3 thin film on Bi2O3-buffered Pt/Ti/SiO2/Si substrate

“…Interestingly, the positive E c for both films is easier to become saturated but higher than the negative one. Such asymmetric E c has been demonstrated to be related to the aging phenomenon occurred in the chemical-solution derived BFMO and BFZO films annealed layer-by-layer [18,19]. However, the BFMO films in the present work were prepared using the conventional annealing method, i.e., the films crystallized during the final annealing treatment.…”

“…Meanwhile, the aging will occur in the films because the annealing temperature is much lower than the Curie temperature of BFMO. The aging can make the asymmetry of E c in BFMO films more severe as proposed by Cui et al [19].…”

“…Particularly, an evident asymmetric coercive field can be observed in the film annealed layer-by-layer. The authors attributed this phenomenon to the aging effect as in the Zn-doped BFO films [19,20].…”

Enhanced ferroelectric properties in BiFe0.95Mn0.05O3 thin films

“…Note that the BFMO films in this work were annealed in N 2 at 525 • C that was much lower than the Curie temperature of BFO (850 • C). Therefore, aging can inevitably occur because of the formation of defect complexes between (V O 2− )•• and (A 2+ Fe 3+ ) [15,16]. The polarization (P D ) of defect complexes can align along the direction of P S during aging [21], which in turn provides a driving force to hinder the switching of ferroelectric domains and eventually reverse as-switched domains to their original orientations (i.e., domain backswitching) [16].…”

“…Unfortunately, the reported Mn-doped BFO films exhibit a large coercive field (E c > 300 kV/cm) [13,14]. Considering that the BFO-based films may be aged to some extent due to the formation of defect complexes between oxygen vacancies [15,16], it is natural to consider that such a large E c is not an intrinsic characteristic of BFO but should be due to that the ferroelectric domains in the aged films are stabilized by the local field produced by defect complexes. Thus, E c could be reduced to a great extent through decreasing the content of (V O 2− )•• in the film.…”