|Place of Conferral||北京|
|Keyword||铁酸铋 电学性能 掺杂 光学性能 溶胶-凝胶|
In recent years, multiferroic material has received extensive attention as a new multifunctional material and BiFeO3 is a typical representative of that. BiFeO3 is a single phase multiferroic material, and is also one of the materials that exhibit both ferroelectricity (TC～850℃) and (anti) ferromagnetic (TN～370℃). At a certain temperature range, the coexisting ferroelctricity and ferromagnetism of multiferroic materials BiFeO3 induce the magnetic-electric effect, which makes BiFeO3 have potential application in multifunctional devices, such as the data storage, spintronics, and sensors. However, BiFeO3 has a large leakage current, which limits its application. Reducing the leakage current is one of the key issues we need to solve. Meanwhile, as a kind of narrow band-gap semiconductor and the unique spontaneous polarization of BiFeO3 may make it overcome the restriction of band gap voltage in conventional solar cell and provide a new approach to the development of efficient stable solar cell in future as well as the relevant photoelectric device. The refractive index and extinction coefficient are important parameters of thin films and determine the mechanical, photoelectric and optical properties of thin films to a certain extent. Therefore, measuring the thickness and optical constants of thin films accurately plays a key role in the preparation and application of thin films. In this paper, BiFeO3 thin film material is the main research object and we focus on the electrical and optical properties of BiFeO3 thin film. At the same time, we discussed the microstructure and properties parameters of BiFeO3 thin film in detail. This article main research content is divided into the following: 1. F doped BiFeO3-xFx (x＝0, 0.02, 0.04, 0.06, 0.08) thin films have been synthesized on ITO/glass substrates using a sol-gel method. X-ray diffraction analysis showed that the obtained samples were highly crystallized and exhibited a single-phase perovskite structure with the space group R3c. The dielectric constants increased with F- ions doping amount increasing. All the films showed an intense dielectric dispersion. The leakage current density decreased with F- ions doping amount increasing. 2. BiFeO3 thin film was prepared on Si substrate annealed at 550℃ via a sol-gel method and we preliminary explored the optical properties of the sample. X-ray diffraction analysis showed that the sample adopted a pure phase. The surface morphology of the sample was characterized by atomic force microscope and the results showed that the surface was smooth and without cracks. The root mean square roughness was 4.87 nm. The refractive index decreased with the increase of wavelength. At short wavelength, the extinction coefficient of the BiFeO3 thin films is very small, so the thin films are nearly transparent nearby this wavelength region. As wavelength increasing, the extinction coefficient increased. BiFeO3 thin films with different Bi excess content were prepared on FTO substrates via sol-gel method taking Fe(NO)3?9H2O and Bi(NO)3?5H2O as starting materials. 2-methoxyethanol is solvent and ice acetic acid is dehydrating agent and catalyst. We studied the effect of excess Bi contents on the microstructure, optical and photovoltaic properties of BiFeO3 thin films. The results showed that, BiFeO3 thin films adopted random orientation. No obvious phase transition was observed with different Bi excess content and the space group was R3c.The grain size of the samples decreased at first and then increased with Bi content increasing. Both of the optical and photovoltaic properties can be tuned by adding different Bi content. BiFeO3 thin film with Bi excess 10 mol% showed the narrowest band gap Eg＝2.31eV.
|徐方龙. 氟离子掺杂及铋过量BiFeO3薄膜的制备与光、电性能研究[D]. 北京. 中国科学院大学,2014.|
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