Study On The Conversion Process From The LDH To Spinel Ferrite And Photovoltaic Study On N-Si(111) Electrodes Modified By MFe₂O₄(M=Mg,Co,Ni) Under Control Of Magnetic Field

Pure single crystal silicon, as an important semiconductor, has already been used in many areas, including molectron, communication technology, computer technology and automatic technology. And it, as the most important solar cell material, has been in the dominant status in the field of battery material. Spinel ferrites, a kind of soft magnetic material with a structural formula of MFe2O4, have many properties such as low melting point, high specific heat, big expansion coefficient, low saturation magnetic moment and low magnetic transition temperature. It can be synthesized under mild conditions.In this paper, some results are realized, including the influence of radius of nonferrous metal ions (Ⅱ) on conversion from M/Fe(Ⅱ)/Fe(Ⅲ) LDH to M/Fe spinel ferrites under mild conditions, synthesis and control factors of spherical spinel ferrites and influence of magnetic field on photoelectric properties of single crystal silicon wafers paved by spinel ferrites. All tasks as follows:1. The MFe2O4 is synthesized from M2+/Fe2+/Fe3+-LDH(M=Mn, Co, Zn, Ni) crystallites at different aged temperature under 1.0 atm。Results indicate that the contents of spinel ferrites are increasing with the increasing of radius of nonferrous metal ions (Ⅱ) and the samples'aged temperature going up.2. Sphere Co-spinel ferrites were prepared by aging Mg2+/Fe2+/Fe3+-LDH (layered double hydroxides) suspension at temperature below 100℃.The product has been characterized by XRD, FTIR, SEM and VSM method, through which the good dispersing sphere particles with the average diameter of approximately 1.0μm were observed. It was also found that many factors had great influence on synthesize of sphere Co-spinel ferrites. The sphere Co-spinel ferrites had greater diameter with the increasing of he pH value of the solutions. The external magnetic field could make sphere spinel ferrites have greater diameter and more perfect structure. The formation of sphere Co-spinel ferrites was favored with a higher molar ratio of ferrous ion in the LDH precursors, but it had greatest particle diameter when the molar ratio of metal ions Co2+:Fe2+:Fe3+ in the cast material was 1:1:1. Compared with MgFe2O4 and NiFe2O4, Co-spinel ferrites had greatest particle diameter. The corresponding discussions to the above results were given in the paper.3. The pure MFe2O4 spinel ferrites obtained at low temperature were adsorbed on the surface of mono-crystalline silicon wafers with the terminal Si-H group through the physical adsorption (M = Mg, Ni and Co). As the MFe2O4 spinel ferrites were soft magnetic material, we can control their distribution on the surface of mono-crystalline silicon wafers, and their magnetisms through controlling the external magnetic field (M = Mg, Ni and Co). The spinel ferrites can be directionally arrayed on the surface of mono-crystalline silicon wafers through controlling the external magnetic field. Compared to the haphazard arrangement, the order arrangement can enhance the photoelectric properties of mono-crystalline silicon wafers. In the optical test, the existence of the external magnetic field can further promote the photoelectric properties of mono-crystalline silicon.