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Spin-Injection Dynamics and Eects of Spin Relaxation in Self-Assembled Quantum Dots of CdSe
T. Furuta,K. Hyomi,I. Souma,Y. Oka,A. Murayama,D. Dagnelund,I. A. Buyanova,W. M. Chen 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.1
We study the spin injection dynamics and the eects of spin relaxation in self-assembled quantum dots (QDs) of CdSe coupled with a diluted magnetic semiconductor (DMS) layer of ZnMnSe, where spin-polarized excitons can be injected from the DMS into the QDs because of the potential dierence. The degree of circular polarization, P, of excitonic photoluminescence (PL) at 5 T in the coupled QDs shows a rapid increase with increasing delay time after a linearly polarized pulse excitation, indicating the spin-injection dynamics. The P value tends to decay gradually because of the exciton-spin relaxation in the QDs after the spin injection. The spin-polarized excitons in the QD ensemble migrate simultaneously from QDs with higher exciton energies to those with lower exciton energies. This inter-dot transfer of excitons also aects the P value in the lower energy region of the QD-emission band because the excitons lose their spin polarizations due to the spin relaxation in the dots during the migration. The detailed analysis for the exciton-spin transfer is presented in a coupled QD system after spin injection. We study the spin injection dynamics and the eects of spin relaxation in self-assembled quantum dots (QDs) of CdSe coupled with a diluted magnetic semiconductor (DMS) layer of ZnMnSe, where spin-polarized excitons can be injected from the DMS into the QDs because of the potential dierence. The degree of circular polarization, P, of excitonic photoluminescence (PL) at 5 T in the coupled QDs shows a rapid increase with increasing delay time after a linearly polarized pulse excitation, indicating the spin-injection dynamics. The P value tends to decay gradually because of the exciton-spin relaxation in the QDs after the spin injection. The spin-polarized excitons in the QD ensemble migrate simultaneously from QDs with higher exciton energies to those with lower exciton energies. This inter-dot transfer of excitons also aects the P value in the lower energy region of the QD-emission band because the excitons lose their spin polarizations due to the spin relaxation in the dots during the migration. The detailed analysis for the exciton-spin transfer is presented in a coupled QD system after spin injection.
Nanosilicon for single-electron devices
H. Mizuta,Y. Furuta,T. Kamiya,Y. T. Tan,Z.A.K. Durrani,S. Amakawa,K. Nakazato,H. Ahmed 한국물리학회 2004 Current Applied Physics Vol.4 No.2-4
This paper presents a brief overview of the physics of nanosilicon materials for single-electron device applications. We study howa nanosilicon grain and a discrete grain boundary work as a charging island and a tunnel barrier by using a point-contact transistor,which features an extremely short and narrow channel. Single-electron charging phenomena are investigated by comparing as-prepared devices and various oxidized devices. The optimization of grain and grain-boundary structural parameters is discussed forimproving the Coulomb blockade characteristics and realizing room temperature device operation.
Applicability of Nuclear Reaction Models Implemented in PHITS to Simulations on Single-event Effects
S. Abe,S. Hirayama,Y. Watanabe,N. Sano,Y. Tosaka,M. Tsutsui,H. Furuta,T. Imamura 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
The nuclear reaction models implemented in the PHITS (Particle and Heavy Ion Transport code System), i.e., the INC model, the QMD model and "event generator mode (e-mode)" with the JENDL-3.3 are validated to apply it to simulations on single-event effects. The model calculations are compared with available experimental data of light-ion (proton and alpha particle) production from neutron-induced reactions on ^(nat)Si and ^(16)O for neutron energies below 100 MeV. Since there is no measurement of lightion production from Si for neutron energies more than 100 MeV, proton-induced reactions on ^(27)Al are also used in the model validation. Comparisons of calculated and measured data for lightion production show that the e-mode calculation with JENDL-3.3 provides better agreement with the experimental data below 20 MeV than the INC and QMD models, and the QMD model reproduces them well above 20 MeV.