未掺杂ZnO中的点缺陷诱导磁性及其调控方法研究

The purpose of this study is to clarify the origin of the ferromagnetism in un-doped ZnO, induced by the defects, to devise new ways to enhance this defects-induced ferromagnetism in controlling the defects involved in un-doped ZnO, and to investigate the thermal stability of this ferromagnetism. We propose that by study experimentally the dependence of the ferromagnetism of un-doped ZnO on those intrinsic defects such as oxygen vacancy, Zn vacancy, oxygen interstitials and Zn interstitials, to make clear the origin of this defects-induced ferromagnetism. Based on this knowledge, we plan to study the influence of annealing in a strong magnetic field on the defects involvement in the un-doped ZnO, thus to find ways to selectivly introduce specific defects in the un-doped ZnO, thus to enhance this defects-infuced ferromagnetism. The third part whould be the investigation on the thermal stability of the defects-induced ferromagnetism in un-doped ZnO, which is always of importance for applications of the materials. This study could be very helpful to understanding of the origin of ferromagnetism in metal oxides induced by defects, and maybe very helpful in devising new ways or methodologies such as thermal annealing in strong magnetic field, to better control the procedure of defects involvement and enhance the ferromagnetism. It may also provide deeper understanding of the relationship between the physical properties of the materials and the defects.

本项目拟研究未掺杂氧化锌中缺陷诱导磁性的起因、磁性强弱的调控方法、以及缺陷诱导磁性的稳定性等问题。通过系统的实验研究，（1）拟澄清在未掺杂ZnO 中，铁磁性的来源与其中的本征缺陷如：氧空位、锌空位、氧间隙、锌间隙等之间的直接关系，以及其磁性强弱与特定缺陷之间的关联性；（2）探索通过强磁场中退火等手段控制ZnO 中特定缺陷的引入过程，实现调控该磁性强弱的可能性和技术方法；（3）获得上述缺陷诱导的铁磁性在不同温度下的演变行为。 本研究项目的完成，有利于深入理解ZnO 等氧化物中缺陷诱导磁性的来源，发展缺陷选择性引入控制技术（如：强磁场中退火等）、以及缺陷同相关物理性能之间的关联性等科学问题的理解。

未掺杂氧化物中点缺陷诱导磁性研究是目前稀磁材料研究中的一个关注点。本项目利用脉冲电子束沉积、电子束沉积等方法制备了ZnO、ZrO2、HfO2等薄膜材料。利用退火处理在这些氧化物中产生点缺陷，并利用强磁场处理调控点缺陷的种类与浓度。通过磁性测量与缺陷分析（光致发光、正电子湮灭、电子顺磁共振、XPS等）研究，证实了未掺杂ZnO中的缺陷磁性来自于其中的氧空位，并且发现了磁性大小与带有单个正电荷的氧空位波那个度之间存在着线性关联。在非晶HfO2薄膜中发现了磁性的存在以及磁性与氧缺陷之间的关联性。此外，观察到未掺杂ZrO2薄膜中的缺陷磁性，并发现该磁性同氧化锆的晶体结构与氧空位有关。具体研究结果表明，未掺杂氧化锆薄膜中的缺陷磁性来自于正交结构氧化锆中的带有单个正电荷的氧空位，其磁性大小同该氧空位浓度存在着线性关系。研究发现，在退火过程中引入强磁场可以实现对氧缺陷浓度以及磁性的调控。