室温铁磁性蒲公英状氧化锌的制备及生长机理研究

以锌粉、醋酸锌和氢氧化钠为原料,采用水热法制备出了具有结构性缺陷的蒲公英状ZnO。通过X射线衍射仪、扫描电子显微镜、荧光光谱仪和超导量子干涉仪对产物的结构形貌和光学性能及磁学性能进行了表征,并对其生长机理进行了探讨。研究表明,蒲公英状氧化锌为六方纤锌矿结构,由许多顶端为锥尖形的棒自组装而成;其荧光本征发射峰在388nm处,属于激子跃迁发射。在波长450～492nm处所观察到的3个弱蓝光峰是由锌填隙原子中的电子到价带顶的跃迁所致;在波长492～580nm范围内出现的较为宽泛的绿光发射峰根源于电子从导带底到氧错位缺陷能级间的跃迁。蒲公英状ZnO中存在的结构性缺陷使得原本呈现抗磁性的ZnO具有了室温铁磁性,从而可作为一种稀磁半导体应用到自旋电子学领域中。

Fabrication and Growth Mechanism of Dandelion-like Zinc Oxide with Room-temperature Ferromagnetism

Dandelion-like ZnO with structural defects were fabricated by a hydrothermal method,using zinc powder,zinc acetate,and sodium hydroxide as raw materials.Phase structures,morphologies,optical,and magnetic properties of the products were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),fluorescence spectrometer,and Quantum Design SQUID MPMS-XL7 magnetometer.The growth mechanism was also investigated.The results show that the ZnO products belong to a hexagonal wurtzite structure,and are composed of numerous cone-tipped ZnO nano-rods.The intrinsic ultraviolet emission peak at 388 nm represents the exciton transition emission.Three evident blue emission peaks,found at the range from 450 to 492 nm,could be attributed to the transition of electrons in interstitial zinc atom on top of the valence bands.The broad green emission peak,located at 492—580 nm,may result from the electron-transition at the bottom of the conduction bands to the energy levels of oxygen mismatch defects.The structural defects endow these dandelion-like ZnO nano-rods with room-temperature ferromagnetism rather than diamagnetism,giving promise in applications of dilute magnetic semiconductor.