Preparation, Structure And Physical Properties Study Of LuFeO₃ And LuFe₂O₄ (LuFeO₃)_n (n=1) Material

With the Feature Size of the semi-conductor decreases by year, the quantum effect of the devices becomes non-ignorable; the traditional Semi-conductor Planar techniques have been in great challenge. Within this background, electron spin science has become one of the focuses. Ferro-electric material is a kind of material which its spontaneous polarization could be changed if another external electric field is applied to the material. According to this special feature, the ferro-electric material has attracted more and more scientist's concern. ReFeO3 and ReFe2O4 (Re=Rare Earth) is a new type of ferro-electric material which is hot recently, because this material always combines ferro-electrics and ferro-magnetism within one material. When the chemical compositions or the crystal structure changes, the material will exhibit plenty of new performances in electrics, phonics, magnetism and so on, thus, the material illustrates a good prospect of application and extension in the future. LuFe2O4(LuFeO3)n(n=1)and LuFeO3 is a kind of this material, Finding out the exact performance of this material has attracted many scientists'great interest. In This paper, LuFe2O4 (LuFeO3) n (n=1) and LuFeO3 material were prepared by sol-gel method, solid-state reaction, PLD, etc. and the structural, surface, photonic, electrical properties are investigated by XRD, AFM, PL, etc. The main results obtained are as follows:(1) The precursor of LuFeO3 dielectric material are prepared with the method of liquid deposition. Then the precursors are calcined from 850℃-1200℃in the method of solid-state reaction. The samples all show ferromagenitism at room-temperature, the sample calcined at 1200℃have the largest remanent magnetization.1. From the XRD spectrum of the sample, The LuFeO3 material begins to crystallize at 850℃. When the temperature arrives 1200℃, a new type of material Lu3Fe5O12 begins to crystallize.2. From the VSM test, the samples all have complete hysteresis of M-H at room temperature. the sample calcined at 1200℃have the largest remanent magnetization; while the sample calcined in 950℃gets the smallest. From the 850℃to 950℃, the Mr have a small increase; but when the temperature arrives 950℃, the Mr drops a lot. It's considerec that the grain size is a very important factor. The hysteresis are all very narrow, it shows the magnitude loss of the samples are all very small.(2) The electric ferro-electric thin-film LuFe2O4 (LuFeO3)n (n=1) is made on Si substrate with sol-gel method. The structual and dielectric test of the samples shows: 1. when the LuFe2O4 (LuFeO3)n (n=1) thin-films are prepared on Si (100) substrates with sol-gel method, the best anneal temperature is 800℃.2. The LaNiO3, as a bottom layer of the film, promotes the growth of the film in the direction of (001).3. the Ni or Mn doping doesn't influence the thin-film's C-V curve. It is the result of the electric ferro-electric mechanism of this material. Both the samples have showed a dielectric degrease when the frequency increases, and the Ni doped one's dielectric constant is smaller than the Mn doped one. The dielectric constant frequency spectrum has two peaks which is considered to be connected with the dispertion of the crystal lattice.4. The dielectic constant in the C-V curve doesn't increase linearly with the doped Mn consistence, it increases at first, and then it degreases when the 3% Mn doped sample gets the maximum. The tanδstay the same when the consistence of the Mn is between 3% to 5%. The dielectric constant of the sample degreases as the frequency increases while The 3% Mn doped sample has the largest dielectric constant. The dielectric loss degreases at first and increases at last. The major dielectric loss is the polar loss when the consistence of the Mn are higher than 1%.5. From the reflective signature, the forbidden-gap is presumed to be 4.451 ev. The Mn doping does not change the forbidden gap of the material as well as the refraction index. From the PL spectrum, one 756 nm peak can be observed corresponding to the energy 1.64 eV and another 550 nm peak can be observed in the pure sample. It is considered that the 756 nm peak corresponds to the a dual-gap energy level; the 550nm peak is a result of the energy level of oxygen vacancy.(3) The target material of LuFeO3 is sintered in 1200℃with a method of solid reaction, and the LuFeO3 thin film was made by PLD method on Si subtrate, the annealling temperature is 700℃. From the XRD test, it is found that the thin-film deposited on Si substrate is not well grown while the thin-film deposited on LNO/Si substrate is much better.