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Bipolar Resistive Switching Effect in BiFeO3/Nb:SrTiO3 Heterostructure by RF Sputtering at Room Temperature
摘要： The (001) oriented BiFeO3 thin film was deposited on the Nb: SrTiO3 substrate by radio frequency magnetron sputtering technology, and the bipolar resistive switching effect was observed in the BiFeO3/Nb: SrTiO3 heterostructure. The results showed that the ratio between the high resistance and low resistance was more than two orders at a reading pulse of -0.5 V and it exhibited excellent retention over 3600 s. The current density-voltage characteristic was dominated by the space-charge-limited conduction. The resistive switching effect of the structure was attributed to the trapping/detrapping of the charge carriers.
关键词： space-charge-limited conduction,bipolar resistive switching,BiFeO3 films,sputter
更新于2025-09-23 15:22:29
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Significant Enhancement of the Visible Light Photocatalytic Properties in 3D BiFeO3/Graphene Composites
摘要： Bismuth ferrite (BiFeO3, BFO) submicron cubes and 3D BFO/graphene composite materials were synthesized by a simple hydrothermal process. The crystallization processes of the 3D BFO/graphene composites with different graphene oxide (GO) concentrations were studied for their visible light photocatalytic properties. Compared to the single BFO submicron cubes, 3D BFO/graphene composites have greatly improved photocatalytic activity. A high photocatalytic performance is obtained at a GO concentration of 3 mg/mL, with the degradation rate of methylene blue (MB) dye reaching up to 92% in 140 min. The enhancement of photocatalytic activity can be attributed to the large specific surface area and 3D architecture of 3D composites, which provide more transport paths to effectively improve the separation rate of photo-generated electrons and holes. Therefore, 3D BFO/graphene composites have a broad prospect of application in the field of photocatalysis.
关键词： photocatalysis,BiFeO3,methylene blue,hydrothermal
更新于2025-09-23 15:22:29
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Effects of Nd, Al Doping on the Structure and Properties of BiFeO3
摘要： The BiFeO3(BFO) and Bi0.95Nd0.05Fe1-xAlxO3 (x = 0, 0.03, 0.05, 0.075, 0.1) powders were prepared at 200 °C for 24 h by hydrothermal method. The effects of Al doping content on the structure, morphology, magnetic, and photocatalytic properties were studied. X-ray diffraction (XRD) and Fourier transform infrared spectrometer (FTIR) demonstrated the compounds are distorted rhombohedral perovskite structure without any other heterogeneity and structural transition. Field emission scanning electron microscope (FESEM) reflected surface of compounds is a dense, agglomerated sphere. As the concentration of Al3+ increases, a small part of the spherical crystallites eventually becomes cauliflower shape. Energy-dispersive X-ray (EDS) showed the Bi0.95Nd0.05Fe0.95Al0.05O3 sample mainly consists of five elements (Bi, Fe, O, Nd, Al) and atom radio matched well with the formula. Vibrating sample magnetometer (VSM) integrated in a physical property measurement system (PPMS-9) illustrated introducing Nd3+ ions into BFO will enhance its magnetism at room temperature. However, with the increase of non-magnetic ion Al3+ concentration in Bi0.95Nd0.05Fe1-xAlxO3 (x = 0, 0.03, 0.05, 0.075, 0.1), the network structure of Fe-O-Fe was destroyed, which led to the decrease of its net magnetization, so that the hysteresis loop shows paramagnetism. The photocatalytic performance of BFO increased initially and decreased afterwards as Al3+ concentration increased, and the best catalytic performance was achieved at x = 0.05.
关键词： Hydrothermal method,Magnetism,Nd, Al doping,BiFeO3
更新于2025-09-23 15:21:21
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Enhanced Ferroelectric Photovoltaic Effect in Semiconducting Single-Wall Carbon Nanotubes/BiFeO <sub/>3</sub> Heterostructure Enabled by Wide-Range Light Absorption and Efficient Charge Separation
摘要： The interfacial electronic band structures of photovoltaic heterostructure devices greatly affect their light absorption and charge-transport properties and thus their photovoltaic performance. In this work, we report an enhanced ferroelectric photovoltaic effect in a semiconducting single-walled carbon nanotube (S-SWCNTs)/ferroelectric BiFeO3 (BFO) heterostructure. A wide range of light absorption was possible in this structure owing to the low bandgaps of the S-SWCNTs (0.2–2.1 eV) and BFO (2.2–2.7 eV). The heterostructure also enabled efficient charge separation owing to the strong built-in electric field resulting from the synergic effect of the formation of p–f–n junctions (p-type S-SWCNTs/ferroelectric (f) BFO/n-type Nb:SrTiO3) and the introduction of a polarization-mediated internal field in the ferroelectric BFO layer. Compared with a single-layer device (Pt/BFO/Nb:SrTiO3), the heterostructure device (Pt/S-SWCNTs/BFO/Nb:SrTiO3) exhibited substantial enhancement of the photovoltaic performance. The open-circuit photovoltage and short-circuit photocurrent density reached up to 0.23 V and ?7.52 mA cm?2 (corresponding to a photo-conversion efficiency of 4.40%) under one-sun illumination, respectively, after optimization of the ferroelectric layer thickness and appropriate interfacial band alignment. Moreover, by applying switchable electric polarization, this heterostructure could be tuned, enabling the development of controllable photovoltaic devices. Our findings demonstrate that the synergistic integration of materials with different functionalities is a promising approach for the design of photovoltaic devices with tunable performance.
关键词： BiFeO3,light absorption,single-walled carbon nanotube,heterostructure,charge separation,ferroelectric photovoltaic effect
更新于2025-09-23 15:21:01
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Study of BiFeO3 thin film obtained by a simple chemical method for the heterojunction-type solar cell design
摘要： Polycrystalline BiFeO3 (BFO) films of different thickness were synthesized by a 2-methoxyethanol (acid)-free simple chemical method. A rhombohedral-type pure phase with a crystallite size less than 18.8 nm was obtained. SEM micrographs showed that BFO has a flat and homogeneous morphology when it was deposited on different semiconductor substrates (ZnO, Ni doped ZnO, and CdS). The highest roughness value (8.6 nm) was observed when BFO was deposited on CdS. The optical response showed that the optical band gap slightly changes as thickness increases. The photovoltaic response of the BFO film was assessed employing different solar cell architectures (p-BFO-n and BFO-n). The results showed that the solar cell based on the Ag/PbS/BFO/CdS/FTO/glass structure presented a short-circuit current density of JSC ? 239:6 mA=cm2 and a power conversion efficiency of h ? 7:65 (cid:2) 10(cid:3)3 %. Photoelectrochemical and ferroelectric measurements were employed to explain the photovoltaic response.
关键词： Mott-Schottky,XPS,PFM,BiFeO3 thin films
更新于2025-09-23 15:21:01
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Effect of non-metallic X(X=F, N, S) and Cr co-doping on properties of BiFeO3: A first-principles study
摘要： In this study, the structural, magnetic, electric and optical properties in X (X=F, N, S) and Cr co-doped BiFeO3 (BFO) are calculated using the density functional theory. For Cr–X co-doping case, the structure of BFO undergo a phase transition from monoclinic to triclinic structure accompanying net magnetic moments of 5.92 μB, 6.04 μB and 7.80 μB, for Cr–F co-doping, Cr–N co-doping and Cr–S co-doping, respectively. The underlying physical mechanisms are the lattice distortions tunned by doping. The decreased Fe–O–Fe bond angles and Fe–O bond lengths will bring weak antiferromagnetism superexchange interaction. In addition, the band gaps of Cr–X co-doping cases are decreased from 2.20 eV (BFO bulk) to 1.31 eV and 1.80 eV for Cr–F co-doping and Cr–S co-doping, respectively, which are well for photovoltaic applications according to the well-known Shockley-Queisser criterion, suggesting a possible great improvement optical properties in Cr–X co-doped samples.
关键词： Lattice distortion,Optical properties,Non-metal and transition-metal co-doped BiFeO3,Magnetic moments
更新于2025-09-23 15:21:01
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Dielectric relaxation and resistive switching of Bi0.96Sr0.04Fe0.98Co0.02O3/CoFe2O4 thin films with different thicknesses of the Bi0.96Sr0.04Fe0.98Co0.02O3 layer
摘要： Bi0.96Sr0.04Fe0.98Co0.02O3/CoFe2O4(BSFCO/CFO) bilayered thin films with different thicknesses of the BSFCO layer are synthesized on FTO/glass substrates by chemical solution deposition method (CSD). The influence of BSFCO thickness on the microstructure, dielectric relaxation, ferroelectric properties and resistive switching (RS) of the thin films are researched. Strain exists in the prepared thin films and gives rise to structural distortion, which has an effect on charged defects and ferroelectric polarization. Dielectric relaxation that is closely related to the interfacial polarization at the BSFCO/CFO interface is observed, and the dielectric loss peaks along with decreasing intensity shift to high frequency with decreasing strain. The Maxwell-Wagner two-layer model is adopted to investigate the mechanism of dielectric relaxation, and the relaxation time τ is calculated and it shown to be directly proportional to the strain. It is found that the dielectric properties, including low dielectric loss, can be improved by controlling the BSFCO layer thickness. The ferroelectric properties improve with the decreasing strain, the 12-BSFCO/CFO thin film possesses a large Pr~102.9 μC/cm2 at 660 kV/cm. The observed resistive switching (RS) behavior is attributed to the interfacial conduction mechanism, it is found that strain-dependent the ferroelectric polarization switching modulates the width of depletion layer and the height of potential barrier at the interface, resulting in the different resistance states.
关键词： dielectric relaxation,bilayered thin film,BiFeO3,resistive switching,strain
更新于2025-09-23 15:21:01
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Polarization driven self-biased and enhanced UV - visible photodetector characteristics of ferroelectric thin film
摘要： In this work, a self-powered UV?visible photodetector characteristics of the polycrystalline BiFeO3 thin film exhibiting pronounced photo-response under both UV and visible light are demonstrated. Interestingly, the film displays switchable photodetector characteristics in accordance with the polarization switching properties and thereby confirms the role of polarization driven depolarization field on the observed properties. Importantly, the photodetector performance parameters such as responsivity (23.9 × 10?4 AW?1), detectivity (2.2 × 1010 Jones), photoconductive gain (8.5 × 10?3), and external quantum efficiency (5.3 %) observed under UV light are 2 to 4 order of magnitude higher than the values reported in similar oxide ferroelectric systems. These studies establish the application of polycrystalline BiFeO3 film as a self-powered UV ? visible photodetector.
关键词： BiFeO3,ferroelectrics,thin-film,UV ? visible photodetector,self-powered
更新于2025-09-23 15:19:57
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The challenge in realizing an exchange coupled BiFeO3- double perovskite bilayer
摘要： In this work we propose a device design for efficient voltage control of magnetism. The magnetization of a ferrimagnetic double perovskite may be manipulated by an exchange coupled layer of multiferroic BiFeO3. Bilayers of Barium doped BiFeO3 and ferrimagnetic double perovskite Sr2FeMoO6 have been prepared by pulsed laser deposition motivated by the possibility of strong interlayer exchange coupling. While single layers of each material show high quality we observe that in both stacking orders the first layer decomposes during the deposition of the second layer. The reason for the decomposition are strongly differing growth conditions for BiFeO3 and Sr2FeMoO6. This means that the generation of artificial multiferroic stacks requires careful choice of the constituent materials to ensure the bilayer stability.
关键词： BiFeO3,Exchange Bias,Double Perovskite,Perovskite,Sr2FeMoO6,Exchange coupling
更新于2025-09-23 15:19:57
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Inorganic photovoltaic cells based on BiFeO <sub/>3</sub> : spontaneous polarization, lattice matching, light polarization and their relationship to photovoltaic performance
摘要： Inorganic ferroelectric perovskite oxides are more stable than hybrid perovskites. However, their solar energy harvest efficiency is not so good. Here, by constructing a series of BiFeO3-based devices (solar cells), we investigated three factors that influence the photovoltaic performance, including spontaneous polarization, terminated ions species in the interface between BiFeO3 and the electrode, and polarized light irradiation. This work was carried out in the framework of density functional theory combined with non-equilibrium Green’s function theory under built-in electric field or finite bias. The results showed that 1) the photocurrent is larger only under a suitable electronic band gap rather than larger spontaneous polarization; 2) the photocurrent reaches the largest in Bi3+ ions terminated interface than in the case of Fe3+ or O2- with SrTiO3 electrode; 3) the photocurrent could be largely enhanced if the polarized direction of the monochromatic light is perpendicular to the spontaneous polarization direction. The results would deepen the understanding of some experimental results of BiFeO3-based solar cells.
关键词： BiFeO3,solar cells,spontaneous polarization,polarized light,photovoltaic performance
更新于2025-09-23 15:19:57