钴离子注入单晶二氧化钛磁性来源与微结构研究
首发时间:2011-12-16
摘要:居里温度高于室温的稀磁半导体材料有望用于自旋电子学器件的开发,因此引起各国研究人员的关注。在室温下,能量为80keV,注量为1×10E17 ions.cm-2的钴离子分别注入到两片长、宽均为10x10mm,厚度为0.5mm的单晶二氧化钛样品,在氮气保护下,样品在温度为900oC的条件下退火30分钟。利用新加坡国立大学物理学部超导量子干涉仪测量样品铁磁性,另外应用X射线衍射(XRD)和扩展边X射线吸收精细结构谱(EXAFS)研究钴离子注入后样品的微观结构。在本研究中,钴离子注入后但未退火的样品在室温下其饱和磁化强度约为0.6×10E-4emu,退火后样品的饱和磁化强度约为0.6×10E-5emu。XRD 和EXAFS研究表明Co在退火后的样品中主要以氧合态形式存在,Co在退火前的样品中主要以团簇形式存在。本文将阐述样品微观结构与铁磁性来源之间的关系。
关键词: 稀磁半导体 二氧化钛 铁磁性 离子注入 EXAFS。
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THE MAGNETIC PROPERTIES AND MICROSCOPIC STRUCTURAL OF A FERROMAGNETIC SEMICONDUCTOR :RUTILE TiO2 SINGLE CRYSTALS IMPLANTED WITH COBALT IONS
Abstract:Ferromagnetic semiconductors with Curie temperatures higher than room temperature are highly desirable for development of spintronic devices. At room temperature, two crystals of rutile(TiO2) were implanted with cobalt ions at an energy of 80 keV by using a fluence of 1×10E17 ions/cm2 and one of the Co-implanted samples was annealed in nitrogen at 900oC for 30min. The magnetic properties of Co-implanted samples were measured with using a superconducting quantum interference device magnetometer (SQUID) at room temperature. Furthermore, the x-ray diffraction (XRD) and extended x-ray absorption fine structure (EXAFS) are applied to describe the structural and compositional properties of Co-implanted samples. In our study, the ferromagnetic behavior of the as-implanted sample is exhibited at room temperature with an effective saturation magnetization of ~0.6×10E-4emu and the annealed sample is ~0.6×10E-5emu. Present studies by XRD and EXAFS indicated that the Co is in a formal oxidation state throughout the implanted region, and there is sufficient evidence showed the presence of cobalt metallic clusters for the as-implanted sample. We will attempt to clarify the relation between ferromagnetic behavior and microscopic structure of the Co-implanted samples in this paper.
Keywords: Ferromagnetic semiconductors, TiO2 Ferromagnetic, Ion Implantation , EXAFS.
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