稀磁ZnO纳米颗粒的生长和性能

Growth and Properties of Diluted Magnetic ZnO Nanoparticles

利用Zn、Fe、Mn、Co的铜铁试剂盐为前驱体,胺为表面包裹剂,在200℃N2保护下生长了2%的过渡金属离子掺杂的ZnO稀磁纳米晶体,研究了纳米晶体的结构、形态、光学和磁学性能。所有ZnO纳米晶体均为近圆形的颗粒,晶体结构为六角纤锌矿结构,无其他氧化物相的析出,但过渡金属离子的掺入使纳米颗粒的尺寸增大。在掺杂纳米颗粒的吸收谱和发射谱中均可以观察到明显的激子吸收和发射峰,所有纳米颗粒在温度高于43K时只有顺磁性。

Capping ZnO nanoparticles doped with 2% Zn, Fe, Mn and Co ions, respectivety, were grown by separately decomposing the mixtures of Zn and Fe, Mn, Co cupferratcs in organic solvent at 200 ℃ under protection of N2. The nanoparticle structure, morphology, optical and magnetic properties were characterized by X- ray diffraction, transmission electron microscope, absorption spectroscopy, photoluminescence spectroscopy and superconducting quantum interference device magnetometer. The concentration of doped ions was measured by electron dispersion spectroscopy and the measured concentration was consistent very well with that in the mixed precursors. Both pure and Fe, Mn or Co doped ZnO nanopartieles are spherical. The average sizes of pure ZnO nanoparticles is 8.5 nm, Mn dope ZnO nanoparticles 12 nm, Fe doped ZnO nanoparticles 14nm and Co doped ZnO nanoparticles 15 nm. Two kinds of precursors were introduced and heterogeneous nucleation occurred during fomlation of doped ZnO nanoparticles. Enlargement of the doped ZnO nanoparticle sizes indicated that Mn-O, Fe-O and Co-O produced by precursor decomposing acres as crystal nucleus during heterogeneous nucleation. Only sharp diffraction of wurtzite ZnO phase was observed in Fe, Mn or Co doped nanoparticles. The doped nanoparticles has a good crystal structure. Exciton absorption of ZnO at 3.47 eV and a broadened band of transitional metal d-d absorption at lower energy were observed. The photoluminescence of nanocrystals doped with Mn and Fe ions is similar. The luminescence is consistent of sharp emission of exciton at 3.30 eV, broaden emission of near band at 3, 18 eV and emission related with defects at 2.94 eV. The nanoparticles doped with Co ions has strong near band emission at 3.14 eV and very weak defect emission at 2.73 eV. All nanoparticles show strong ultraviolet emission. The field-cooled and zero-field-cooled magnetization of Mn, Fe doped ZnO taken at 1. 19 × 10^3 H show no deviation when the temperature is higher than 40 K and the deviation temperature is 43 K in Co doped ZnO nanoparticle. The magnetization of Co doped nanoparticles is larger than that of Fe and Mn doped nanoparticle. All doped nanopartiels show paramagnetie behavior at room temperature.