Abstract
In this study, BFO and BFAO thin films were prepared on fluorine-doped tin oxide (FTO) substrates via spin coating with two different acid solvents. One is nitric acid solution (solvent I), the other is a mixture of 2-methoxyethanol and glacial acetic acid (solvent II). The structure, morphology, elemental valence states, and ferroelectric properties of BiFeO3 (BFO) and BiFe0.96Al0.04O3 (BFAO) films were investigated. X-ray diffraction (XRD) results show that all the films are R3c structure and have no impurity phase. The SEM results show that the BFO thin film prepared by solvent II is more compact, uniform, and has low porosity. Raman spectra show that Al doping causes structural distortion. Al doping can solve the problem of porosity and increase the density of BFO thin film. Therefore, the density of BFAO-II sample is better. X-ray photoelectron spectroscopy (XPS) shows that the presence of Al reduces the oxygen vacancy content. This is beneficial to reduce the leakage current density and improve the ferroelectric properties. The leakage current density of BFAO-II sample is 10-3 A/cm2, and the double residual polarization value is 110.2 μC/cm2. Compared with BFO-II sample, it is significantly improved. In addition, Al doping can reduce the band gap of BFO films. This work will be a new idea for the further application of Al doped bismuth ferrite films.
Highlights
IntroductionMultiferroic materials are a research hotspot. Multiferroics could be characterized by the possession of two or more ferroic order parameters, mainly including ferroelectric, ferroelastic, and ferromagnetic (antiferromagnetic)
At present, multiferroic materials are a research hotspot
Compared to the standard PDF (BiFeO3: PDF#71-2494), it can be concluded that all of the thin film samples remained pure phase, and crystal structures of the samples could be indexed to distorted rhombohedral structure with space group R3c
Summary
Multiferroic materials are a research hotspot. Multiferroics could be characterized by the possession of two or more ferroic order parameters, mainly including ferroelectric, ferroelastic, and ferromagnetic (antiferromagnetic). Multiferroic BiFeO3 (BFO) is a typical Bi-based material, that possesses an excellent ferroelectric order (Curie temperature, TC ~ 830 °C) and G-type antiferromagnetic order (Neel temperature, TN ~ 370 °C). BFO has always been a favorite topical of researchers, including in the forms of zero-dimensional powder [4, 5], one-dimensional fiber [6], two-dimensional film [7], and three-dimensional bulk [8]. These materials can potentially be used in photocatalysis, photovoltaics, phototransduction, energy harvesting devices, sensors, and actuators, because they have excellent photoabsorption and ferroelectric and piezoelectric properties [9-11]. BAO possess an excellent ferroelectric value (Ps ~ 90 μC/cm2) and high Curie temperature (TC ~ 530 °C) [28]. Optimized Al doping BFO films can be used in the construction of generation environmentally friendly intensive nanodevices
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