Investigation On Characteristics Of Rare Earth Sm-Doped 8-hydroxyquinoline-based Organic Molecular Thin Films

As the field of consumer electronics to light,thin,large area,flexible folding,energy saving,biocompatible,wearable and other direction,organic semiconductor materials and device to attract the attention of the world countries,as the semiconductor and electronic areas of the popular frontier direction.Organic semiconductors are composed of light elements,spin-orbit coupling interaction and ultra-fine interaction,so it has a very long spin relaxation time,which is expected to precede the inorganic semiconductor to achieve faster,ultra-low power consumption,data non-volatile multi-functional new spin devices.Since the new century,organic semiconductor-based spin electronic devices such as organic spin valves,organic spin light emitting diodes,organic magnetic tunnel juctions have successfully developed,showing the bright prospects of organic semiconductor materials in the field of spin electronics.However,due to the existence of spin-polarized electrode and organic layer matching problems,the current organic spin devices only have good performance at low temperature,the performance at room temperature is poor.The development of organic semiconducting materials with ferromagnetic properties as spin implanted electrode layer or buffer layer material is expected to solve the problem of spin injection efficiency caused by the mismatch of conductivity,and improve the room temperature performance of spin electronic devices and spin optoelectronic devices.In our paper,we selected 8-hydroxyquinoline-based organic molecular with execellent photoelectric properties and rare earth samarium metal elements,and used vacuum thermal evaporation method to prepare the two kind of rare earth doped 8-hydroxyquinoline-based organic molecular materials.We tested the morphological structure and analyzed the combination of rare earth elements and organic molecules and charge transfer.And also we tested the magnetic properties of the samples,analyzed the magnetic mechanism,obtained the organic small molecule materials with room temperature ferromagnetism,and provided the materials basis for the development of organic spin electronic devices and optoelectronic devices based on the magnetic materials.The optical properties of the samples were tested,and the influence of rare earth doping on the optical properties of the samples was studied.The multifunctional organic materials with ferromagnetic properties,semiconducting conductivity and excellent photoelectric properties were obtained.These provide a material basis for the development of multifunctional and multi-field controlled new spin devices that combine electronics,optics and magnetism.In this thesis,the main contents and conclusions are as follows:??The preparation,structure,magnetic properties and photoelectric properties of rare earth samarium?Sm?-doped Gaq₃.The Sm-doped Gaq₃ films were prepared by co-evaporating pure Gaq₃ and Sm powders.And the room temperature ferromagnetism was observed in the sample,the maximum coercivity was 103.32 Oe,and the saturation magnetization was 4.1×10-6 emu.The results shows that the magnetization and coercivity of the doped films increase with the increase of the doping concentration.In the nominal doping concentration of 15 wt.%to reach the maximum,and then we continue to increase the Sm concentration but the sample magnetic reduction.First we analyzed the structural of the doped films,observed the surface morphology and excluded the factors of the metal Sm clusters.The analysis of the FTIR spectrum shows that the molecular structure of the Gaq₃ molecule did not show any significant change after doping,indicating that the doped metal Sm did not change the structure of Gaq₃.The XPS pattern shows that the metal Sm atom is electronically transferred to the Gaq₃ molecule as the donor atom,which affects the N-Ga bond in the Gaq₃ molecule,forming two new peak position.Then we studied the photoelectric properties of the doped films.Through the measurement of the absorption spectrum,the band gap of thedoped film was obviously widened at the doping concentration of 15 wt.%.It could be understood that the electron of Sm atom are transferred to the pyridine ring,resulting in widening of the band between HOMO and LUMO.We also studied the photoluminescence properties of the doped films.And there was a slight blue shift at low doping concentration,a significant red fluorescence peak at heavy doping concentration.That indicate the doped metal Sm affected the system of the crossing constant?Kisc?.Then we investigated the effect of annealing on Sm-doped Gaq₃ films.??The preparation,structure,and magnetic properties of rare earth samarium?Sm?-doped Mnq₂.The Sm-doped Mnq₂ films were prepared by co-evaporating pure Mnq₂ and Sm powders.Atomic force microscopy AFM study showed that when the mass ratio of rare earth metal Sm was 7 wt.%,the doping film had a rudder roughness of 1.9 nm,which was similar to that of pure Mnq₂ film,indicating that Sm doping had little effect on Mnq₂ surface.Alternating gradient magnetometer test showed that the rare earth doped film exhibited ferromagnetism at room temperature,and the magnetic properties were the strongest at Mn:Sm=5.8:1,and the coercivity was about 103.6 Oe,and the saturation magnetization is about 5.07x10-6 emu.Due to the limitation of the evaporation technique,we have to no way to obtain samples with Sm-doped ratio lower than Mn:Sm=5.8:1.With the increase of Sm metal ratio,the magnetic properties of the samples decreased,and when the Mn:Sm=1:1,the saturation magnetization of the samples decreased to 0.35×10-6 emu.We also studied the room temperature ferromagnetism of metal Dy-doped Mnq₂,and found that this doping system does not occur ferromagnetic signals.