| 41. |
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| 42. |
- Kayanuma, K., et al.
(författare)
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Optical study of spin injection dynamics in double quantum wells of II-VI diluted magnetic semiconductors
- 2005
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Ingår i: AIP Conf. Proc. 772. - : American Institute of Physics (AIP). ; , s. 1387-1388
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The spin injection process is studied in double quantum wells ofZnMnSe and ZnCdSe with a tunneling barrier by circularly-polarized transientphotoluminescence spectroscopy. The result shows two types of spin injectionsin the time ranges of 30 and 1000 ps. Theobserved spin injection processes are quantitatively interpreted by the individualtunneling of electrons and holes based on the rate equationanalysis. ©2005 American Institute of Physics
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| 43. |
- Kayanuma, K, et al.
(författare)
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Transient photoluminescence spectroscopy of spin injection dynamics in double quantum wells of diluted magnetic semiconductors
- 2006
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313 .- 1872-7883. ; 119, s. 418-422
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Tidskriftsartikel (refereegranskat)abstract
- Dynamics of spin injection has been studied in double quantum wells (DQWs) composed of diluted magnetic and non-magnetic semiconductors. Picosecond-transient photoluminescence (PL) of excitons in the DQWs has been measured in magnetic field. In the Cd1-xMnxTe-based DQWs, the PL intensity of the magnetic well (MW) excitons decays faster with decreasing barrier width from 12 to 2 nm. This provides the evidence for carrier tunneling from the MW to the non-magnetic well (NW) through the barrier layer. The degree of circular polarization in the transient PL of the NW exciton in magnetic field shows marked evidence for spin injection and rapid spin relaxation in the DQW system. In the Zn1-yMnySe-based DQWs, the degree of circle polarization in the NW exciton PL at 3T shows a rise with a time constant of 400 ps, while the PL of the MW exciton decays within 50 ps. The observed result is interpreted by the individual spin injection for electrons and holes from the MW to the NW. The results of the transient PL of excitons in the DQWs are compared with the transient absorptions of excitons studied by the pump-and-probe spectroscopy. (c) 2006 Elsevier B.V. All rights reserved.
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| 44. |
- Koyama, T., et al.
(författare)
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Spin dynamics of type-II excitons in diluted magnetic double quantum wells
- 2007
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Ingår i: 28th Int. Conf. on the Physics of Semiconductors,2006. - : American Institute of Physics (AIP). ; , s. 465-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Dynamical properties of the electron and hole spins are demonstrated indouble quantum wells composed of diluted magnetic and nonmagnetic semiconductors.Excitonic photoluminescence of the type-II transition appears for the lower-lyingdown-spin level of the exciton in magnetic field. A type-Iexciton transition is also observed for the opposite up-spin excitonstate. The result shows the spatial spin separation and thespin-injection dynamics for the heavy-hole spin states in the doublequantum wells. ©2007 American Institute of Physics
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| 45. |
- Lindahl, O A, et al.
(författare)
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Tactile resonance sensors in medicine.
- 2009
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Ingår i: Journal of Medical Engineering & Technology. - : Informa UK Limited. - 0309-1902 .- 1464-522X. ; 33:4, s. 263-273
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Tidskriftsartikel (refereegranskat)abstract
- Tactile sensors in general are used for measuring the physical parameters associated with contact between sensor and object. Tactile resonance sensors in particular are based on the principle of measuring the frequency shift, Deltaf, defined as the difference between a freely vibrating sensor resonance frequency and the resonance frequency measured when the sensor makes contact to an object. Deltaf is therefore related to the acoustic impedance of the object and can be used to characterize its material properties. In medicine, tactile resonance sensor systems have been developed for the detection of cancer, human ovum fertility, eye pressure and oedema. In 1992 a Japanese research group published a paper presenting a unique phase shift circuit to facilitate resonance measurements. In this review we summarize the current state-of-the-art of tactile resonance sensors in medicine based on the phase shift circuit and discuss the relevance of the measured parameters for clinical diagnosis. Future trends and applications enabled by this technology are also predicted.
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| 46. |
- Murayama, A., et al.
(författare)
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Dynamics of exciton-spin injection, transfer, and relaxation in self-assembled quantum dots of CdSe coupled with a diluted magnetic semiconductor layer of Zn0.80 Mn0.20 Se
- 2007
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 75:19, s. 195308-
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Tidskriftsartikel (refereegranskat)abstract
- We study the dynamics of exciton-spin injection, transfer, and relaxation in self-assembled quantum dots (QDs) of CdSe coupled with a diluted magnetic semiconductor (DMS) layer of Zn0.80 Mn0.20 Se, where spin-polarized excitons can be injected from the DMS into the QDs. The degree of circular polarization P of excitonic photoluminescence (PL) at 5 T in the coupled QDs exhibits a rapid increase with increasing delay time, up to +0.3 at 25 ps after the pulse excitation of the DMS by a linearly polarized light. This development of a positive P value directly reflects the spin-injection dynamics from the DMS, since the intrinsic polarization of the QD excitons due to Zeeman splitting is P∼-0.1 when only the QDs are selectively excited. The P value gradually decays with time after reaching its maximum, as a result of the exciton-spin relaxation with a time constant of 800 ps in the QDs. Time-resolved circularly polarized PL spectra immediately after the pulse excitation directly show the exciton-energy dependence of the spin-injection dynamics in the QD ensemble, where two-dimensional-like QDs with higher exciton energies show higher receptivity to the spin-polarized excitons than three-dimensional-like dots with lower exciton energies. A rate equation analysis reveals all time constants responsible for the spin-injection dynamics. We deduce a time constant of 10 ps for the spin injection. The spin-injection efficiency of 0.94 is also obtained, which corresponds to the ratio between the number of the spin-polarized excitons responsible for the rise of the positive P value in the QD emission and the total number of the excitons injected from the DMS. Moreover, we observe that interdot exciton transfer significantly affects the P value within the QD emission band after the fast spin injection, in addition to the spin relaxation within the QDs. © 2007 The American Physical Society.
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| 47. |
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| 48. |
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| 49. |
- Oyama, S., Ishii, M., Murayama, Y., Shinagawa, H., Buchert, S., Fujii, R. and Kofman, W.
(författare)
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Generation of atmospheric gravity waves associated with auroral activity in the polar F region
- 2001
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Ingår i: Journal of Geophysical Research. ; 106, s. 18543-
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Tidskriftsartikel (refereegranskat)abstract
- Relations between auroral activities and the generation of neutral-wind oscillations in the polar F region (150-300 km) were investigated using data from the European Incoherent Scatter (EISCAT) radar, the all-sky auroral camera, and the IMAGE (Internatio
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| 50. |
- Park, J. H., et al.
(författare)
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Transfer dynamics of spin-polarized excitons in ZnCdMnSe/ZnCdSe double quantum wells
- 2008
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Ingår i: Journal of the Korean Physical Society. - 0374-4884 .- 1976-8524. ; 53, s. 167-170
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Tidskriftsartikel (refereegranskat)abstract
- We study the transfer dynamics of spin-polarized excitons in diluted magnetic semiconductor (DMS) double quantum wells (QWs) of ZnCdMnSe/ZnCdSe, where the spin-polarized excitons tunnel from the non-magnetic ZnCdSe to DMS-ZnCdMnSe wells and subsequently relax to the ground state in the DMS well with phonon emissions. The exciton-transfer time decreases when the exciton-energy difference between both the wells is equal to the one-LO-phonon energy, indicating the LO-phonon-assisted acceleration of the spin transfer. Moreover, the exciton transfer alters into the separate transfer of the electron and the heavy hole when the electron potential difference becomes larger than the LO-phonon energy. This observation demonstrates the importance of energy-relaxation dynamics in the spatial transport of spins in semiconductor quantum structures.
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