1998 Fiscal Year Final Research Report Summary
Fabrication and Study of Nanostructure Diluted Magnetic Semiconductors
| Project/Area Number |
08555001
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
Applied materials science/Crystal engineering
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| Research Institution | Research Institute for Scientific Measurements, Tohoku University |
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Principal Investigator |
OKA Yasuo RISM Tohoku University, Professor, 科学計測研究所, 教授 (60013520)
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| Co-Investigator(Kenkyū-buntansha) |
MURAYAMA Akihiro Asahi Komag Co.Ltd, Senior Researcher, 開発部主任
J.X. Shen 東北大学, 科学計測研究所, 学振研究員
TAKAHASI Masaaki RISM Tohoku University, Res.Associate, 科学計測研究所, 助手 (80006147)
YANATA Kohei RISM Tohoku University, Res.Associate, 科学計測研究所, 助手 (70006146)
SHEN J.X. RISM Tohoku University, JSPS Fellow
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| Project Period (FY) |
1996 – 1998
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| Keywords | semiconductors / photons / laser / magnetism / nanostructures / thin films / crystal / dimensionarity |
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| Research Abstract |
The objective of this research project is to fabricate new nanostructure lattices composed of diluted magnetic semiconductors (DMSs) and also to study magneto-optical properties of the nanostructures. For this purposes, we have fabricated 2-dimensional quantum wells, 1-dimensional quantum wires, and 0-dimensional quantum dots by molecular beam epitaxy, atomic beam epitaxy, and electron-beam lithography techniques. Materials we have fabricated are Cd_<1-x>Mn_xTe and Cd_<1-x>Mn_xSe with Mn concentration of x= 0.03-0.3.
Obtained these nanostructures have been studied by the ultrafast laser spectroscopy using femto-second pulse lasers. Time resolved photoluminescence has been measured in Cd_<1-x>Mn_xTe quantum wells by the selective excitation of the quantum-well exciton states. The transient behavior of the exciton luminescence clearly shows the formation process of the excitonic magnetic polarons, which is suppressed by the strong external magnetic fields. Quantum dots of Cd_<1-x>Mn_xSe grown by the Stranski-Krastanow mode on ZnSe buffer layers show very fast decay of the excitons in the dots. The lifetime of the quantum dot excitons is markedly increased by the external magnetic fields. The phenomena are interpreted by decrease of the nonradiative process due to the shrinkage of the exciton wavefunction by the magnetic field. Pump-probe transient absorption spectroscopy has been made on Cd_<1-x>Mn_xTe quantum well, The exciton and magnetic polaron dynamics are observed in the 2 ps to 3 ns time region. Quantum wires of Zn_<1-x>Cd_xSe system show the photoluminescence evidence of the 1-dimensional confinement effect as well as the relaxation of the lattice strains by decreasing the wire width. Fabrication of Cd_<1-x>Mn_xSe quantum wires is under progress.
The remarkable magneto-optical effects of the nanaostructure DMSs elucidated in the present project will stimulate the research of the new magneto-optical microdevices.
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