【作者】 邹长伟；

【导师】 付德君；

【作者基本信息】 武汉大学 ， 粒子物理与原子核物理， 2010， 博士

【摘要】 用离子注入和磁控溅射的方法研究了过渡金属元素和锂共掺杂ZnO薄膜的铁电铁磁性质。在ZnO:CoLi和ZnO:CuLi薄膜中发现了室温多铁性,并对其铁磁铁电机制进行了研究。在Mn和Li共掺杂的ZnO中发现了室温铁磁性,同时实现了ZnO的P型掺杂,对ZnO光电子器件的应用有一定的贡献。在(Co,Li)共注入的ZnO中同时发现了室温铁电性和铁磁性。Li和Co的注入能量分别为50和400 Kev,注入剂量分别为1×1016cm-2和5×1016 cm-2。共注入样品在700℃退火后的剩余电偶极化率和矫顽场分别为10.2μC/cm2和24.8kV／cm。700℃退火后的共注入样品的饱和磁化率和矫顽磁场分别为11.4×10-5emu和67 Oe。样品的铁电性可以解释为掺杂离子(Co,Li)与基体阳离子(Zn)的半径差异引起的电偶极化,而铁磁来源于电子和缺陷调制的束缚磁激子。在Pt(111)/Ti/SiO2衬底上用磁控共溅射的方法生长了Zn0.95-xCuxLi0.05O薄膜。用X射线衍射(XRD)、x光电子能谱(XPS)、和光吸收谱(absorption spectroscopy)验证了薄膜为多晶材料,并且Cu2+离子替代Zn2+位Zn0.90Cu0.05Li0.05O薄膜在电学和磁学测试中显示出电滞回线和磁滞回线,剩余电极化率和饱和磁化率分别为6μc/cm2和0.43μB/cm2。对于样品的铁电性和铁磁性机制在结论中进行了讨论。用磁控共溅射的方法在玻璃衬底上生长了一系列的Zn0.95-xMnxLi0.05O (x=0.01,0.03,0.05 and 0.08)薄膜,发现其窒温铁磁性质与缺陷有关。Zn0.95-xMnxLi0.05O薄膜的c轴晶格常数,禁带宽度,矫顽场和剩余磁化率随Mn掺杂量的增加而增加。通过比较沉积前后薄膜的结构和磁学性质,我们发现空穴载流子和缺陷浓度在Mn和Li共掺杂ZnO的铁磁性能中有重要的作用。薄膜的铁磁性质可以解释为缺陷束缚载流子相关的束缚磁激子模型(BMP)。多铁材料在自旋电子学器件和存储器中有广泛的应用,我们通过用共掺杂的方法实现了室温多铁性,初步探索了宽禁带ZnO半导体在多铁材料中的用途。通过掺杂稀土元素,如Gd, Er等,可以实现较大的矫顽磁场和饱和磁化率更多还原

【Abstract】 We have studied the ferroelectricity and ferromagnetism properties of TM and Li co-doped ZnO films deposited by implantation and reactive magnetron sputtering. The multiferroic property was found in ZnO:CoLi and ZnO:CuLi films and the ferromagnetism mechanism was studied. Additionally, we found room temperature ferromagnetism and p-type doping in Mn and Li co-doped ZnO films which have great contribution for the application in photoelectric device.Simultaneous room temperature ferroelectricity and magnetism was observed in (Co, Li) co-implanted ZnO films. The implantation were conducted for Li and Co at energies of 50 and 400 keV, respectively, to doses of 1×1016cm-2 and 5×1016 cm-2. Remnant dipole polarization of 10.2μC/cm2 and coercive electric field of 24.8 kV/cm were recorded for co-implanted ZnO films annealed at 700℃. The implanted samples annealed at 700℃also exhibited a saturation magnetization over 11.4×10-5 emu and coercive magnetic field of 67 Oe. The ferroelectricity is interpreted by the ionic radius difference between the dopants and host cations, and the magnetism is explained by bound magnetic polarons mediated by electrons and defects.Single-phase Zn0.95-xCuxLi0.05O thin films have been prepared on Pt (111)/Ti/SiO2 substrates by reactive magnetron sputtering method. The XRD, XPS and absorption measurements confirmed the polycrystalline nature of the films and the substitution of Zn2+ by Cu2+ ions. The sputtered Zn0.90Cu0.05Li0.05O film shows multiferroic properties exhibiting a saturated ferroelectric loop with a remanent polarization of 6μc/cm2 and a saturated loop with a saturation magnetization of 0.43μB/Cu at room temperature. The origins of the ferromagnetism and ferroelectricity in these films are discussed.We report on defects related room temperature ferromagnetic characteristics of Zn0.95-xMnxLi0.05O (x=0.01,0.03,0.05 and 0.08) thin films grown on glass substrates using reactive magnetron sputtering. By increasing the Mn content, the films exhibited increases in the c-axis lattice constant and fundamental band gap energy, coercive field and remanent magnetization. Comparison of the structural and magnetic properties of the as-deposited and annealed films indicates that the holes carriers, together with defects concentrations, play an important role in the ferromagnetic origin of ZnMnO. The ferromagnetism in films can be described by bound magnetic polaron models with respect to defect-bound carriers.Multiferroic materials have great application in spintronics and photoelectric devices. We preliminarily study the multiferroic propreties of ZnO films by co-doping methods, and find room temperature ferromagnetism and ferroelectricity in Me and Li co-doped ZnO film. By co-doping with RE (rare earth) elements, such as Gd and Er, we hope to doposit ZnO films with superior coercive magnetic field and saturation magnetization.更多还原