2005 Fiscal Year Final Research Report Summary
Properties of nano-scale artificial structures of magnetic semiconductors and search for new functionalities
| Project/Area Number |
14076205
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| Research Category |
Grant-in-Aid for Scientific Research on Priority Areas
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| Allocation Type | Single-year Grants |
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| Review Section |
Science and Engineering
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| Research Institution | University of Tsukuba |
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Principal Investigator |
TAKITA Koki University of Tsukuba, Graduate School of Pure and Applied Siences, Professcr, 大学院数理物質科学研究科, 教授 (00011213)
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| Co-Investigator(Kenkyū-buntansha) |
OZAKI Nobuhiko University of Tsukuba, Graduate School of Pure and Applied Sciences, Lecturer, 大学院数理物質科学研究科, 講師 (30344873)
KURODA Shinji University of Tsukuba, Graduate School of Pure and Applied Sciences, Associat Professor, 大学院数理物質科学研究科, 助教授 (40221949)
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| Project Period (FY) |
2002 – 2005
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| Keywords | Spintronics / Ferromagnetic semiconductors / Molecular beam epitax / Carrier doping / Clusters / Self-organized dots |
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| Research Abstract |
In this research project, we have been engaged in the exploitation of novel semiconducting materials exhibiting ferromagnetism at room temperature, which are considered to be indispensable for future spintronics utilizing spin degree of freedom of electrons. We have studied (Zn,Cr)Te, which has been attracting attention as o ne of the candidates of intrinsic room-temperature ferromagnetic semiconductors. Specifically, we have investigated how the magnetic properties are altered by co-doping of charge impurities of both p-type and n-type, aiming at the elucidation of the origin of ferromagnetism and the device application. As a result, we have found that the ferromagnetism of (Zn,Cr)Te is suppressed due to the co-doping of nitrogen as a p-type dopant while the ferromagnetism is significantly enhanced due to the co-doping of iodine as an n-type dopant. The structural and chemical analyses using transmission electron microscope (TEM) and energy-dispersive X-ray spectroscopy (EDS) have revealed that the Cr distribution in the grown films is modified due to the co-doping ; the Cr distribution in the iodine-doped films is strongly inhomogeneous, with the formation of Cr-rich regions of a typical size of 30〜50 nm, while the Cr distribution in the undoped and nitrogen-doped films is almost homogeneous. These results indicate that an significant increase of ferromagnetic transition temperature Tc in the iodine-doped (Zn,Cr)Te is caused by the formation of ferromagnetic clusters containing high Cr contents. As an origin of different homogeneities of the Cr distribution depending on the co-doping, we propose a model that the change in Cr valence due to the co-doping of charge impurities affects the attractive interaction between Cr ions, resulting in the formation of Cr-rich clusters.
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