Wang Xuefeng, Zheng Rongkun, Liu Zongwen, Ho Ho-Pui, Xu Jianbin, Ringer Simon P
Australian Key Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006, Australia. Department of Electronic Engineering, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, People's Republic of China. Jiangsu Key Laboratory of Thin Films and Department of Physics, Suzhou University, Suzhou 215006, People's Republic of China.
Nanotechnology. 2008 Nov 12;19(45):455702. doi: 10.1088/0957-4484/19/45/455702. Epub 2008 Oct 9.
Co-doped ZnO nanorods (composition: Zn(0.955)Co(0.045)O) were grown by a simple surfactant-assisted hydrothermal technique. The morphological, structural, optical and magnetic properties of the as-prepared nanorods were investigated by means of scanning electron microscopy, high-resolution transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, micro-Raman spectroscopy, micro-cathodoluminescence, and vibrating sample magnetometry (VSM). The results showed that the sample had rod-like morphology and that the preferential growth direction was along the c axis. While Co was successfully doped into the ZnO wurtzite lattice structure as revealed by several characterization techniques, hidden secondary phases of Zn(y)Co(3-y)O(4) (0≤y≤1) were also clearly detected by the micro-Raman spectroscopic technique. We propose that the predominant diffusion-limited Ostwald ripening crystal growth mechanism under the hydrothermal coarsening yielded such phase segregation. VSM results showed that the nanorods displayed relatively weak room-temperature ferromagnetism. We suggest that the origin of the ferromagnetism is probably due to the presence of the mixed cation valence of Co via a d-d double-exchange mechanism rather than the real doping effect. It is essential to control the crystal growth mechanism and defect states associated with the ferromagnetism in order to realize the intrinsic diluted magnetic semiconductors.
通过一种简单的表面活性剂辅助水热技术生长了共掺杂的ZnO纳米棒（组成：Zn(0.955)Co(0.045)O）。利用扫描电子显微镜、高分辨率透射电子显微镜、X射线衍射、X射线光电子能谱、显微拉曼光谱、显微阴极发光和振动样品磁强计（VSM）对所制备纳米棒的形态、结构、光学和磁性进行了研究。结果表明，样品具有棒状形态，且择优生长方向沿c轴。几种表征技术表明Co成功掺杂到ZnO纤锌矿晶格结构中，同时显微拉曼光谱技术也清晰地检测到了隐藏的Zn(y)Co(3 - y)O(4)（0≤y≤1）第二相。我们认为，水热粗化过程中主要的扩散限制奥斯特瓦尔德熟化晶体生长机制导致了这种相分离。VSM结果表明，纳米棒在室温下表现出相对较弱的铁磁性。我们认为，铁磁性的起源可能是由于Co通过d - d双交换机制存在混合阳离子价态，而不是真正的掺杂效应。为了实现本征稀磁半导体，控制与铁磁性相关的晶体生长机制和缺陷状态至关重要。
