| 1. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Optical characterization of ZnMnO-based dilute magnetic semiconductor structures
- 2006
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Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 24:1, s. 259-262
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Tidskriftsartikel (refereegranskat)abstract
- n -type ZnMnO spin injection layers were grown by pulsed laser deposition on top of n-ZnMgOZnOp-AlGaNp-GaN hybrid spin light-emitting diode (LED) structures synthesized by molecular-beam epitaxy. Both the ZnMnOZnMgOZnOAlGaNGaN structures and control ZnMnO samples show no or very low (up to 10% at the lowest temperatures) optical (spin) polarization at zero field or 5 T, respectively. This indicates difficulties in generating spin polarization by optical spin orientation or possible efficient spin losses. The results are similar to those found earlier for GaMnNInGaNAlGaN spin-LED structures and indicate that these wide-band-gap dilute magnetic semiconductors with weak spin-orbit interaction and hexagonal symmetry are not attractive for spin-LED applications. © 2006 American Vacuum Society.
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| 2. |
- Pearton, S. J., et al.
(författare)
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Ferromagnetism in transition-metal doped ZnO
- 2007
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Ingår i: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 0361-5235 .- 1543-186X. ; 36:4, s. 462-471
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Forskningsöversikt (refereegranskat)abstract
- ZnO is an attractive candidate for spintronics studies because of its potential for exhibiting high Curie temperatures and the relative lack of ferromagnetic second phases in the material. In this paper, we review experimental results on transition-metal (TM) doping of ZnO and the current state of theories for ferromagnetism. It is important to re-examine some of the earlier concepts for spintronics devices, such as the spin field-effect transistor, to account for the presence of the strong magnetic field that has deleterious effects. In some of these cases, the spin device appears to have no advantage relative to the conventional charge-control electronic analog. We have been unable to detect optical spin polarization in ZnO.
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| 3. |
- Pearton, Stephen J., et al.
(författare)
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Transition Metal Doped ZnO for Spintronics
- 2007
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Ingår i: MRS Proceedings 2007 vol. 999. - Warrendale, PA : Materials Research Society. ; , s. 0999-K03-K04
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- ZnO is a very promising material for spintronics applications, with many groups reporting room temperature ferromagnetism in films doped with transition metals during growth or by ion implantation. In films doped with Mn during PLD, we find an inverse correlation between magnetization and electron density as controlled by Sn doping. The saturation magnetization and coercivity of the implanted single-phase films were both strong functions of the initial anneal temperature, suggesting that carrier concentration alone cannot account for the magnetic properties of ZnO:Mn and factors such as crystalline quality and residual defects play a role. Plausible mechanisms for the ferromagnetism include the bound magnetic polaron model or exchange is mediated by carriers in a spin-spilt impurity band derived from extended donor orbitals. Spin-dependent phenomena in ZnO may lead to devices with new or enhanced functionality, such as polarized solid-state light sources and sensitive biological and chemical sensors.
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| 4. |
- Pearton, S.J., et al.
(författare)
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ZnO doped with transition metal ions
- 2007
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Ingår i: IEEE Transactions on Electron Devices. - 0018-9383 .- 1557-9646. ; 54:5, s. 1040-1048
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Tidskriftsartikel (refereegranskat)abstract
- Spin-dependent phenomena in ZnO may lead to devices with new or enhanced functionality, such as polarized solid-state light sources and sensitive biological and chemical sensors. In this paper, we review the experimental results on transition metal doping of ZnO and show that the material can be made with a single phase at high levels of Co incorporation (~ 15 at.%) and exhibits the anomalous Hall effect. ZnO is expected to be one of the most promising materials for room-temperature polarized light emission, but to date, we have been unable to detect the optical spin polarization in ZnO. The short spin relaxation time observed likely results from the Rashba effect. Possible solutions involve either cubic phase ZnO or the use of additional stressor layers to create a larger spin splitting in order to get a polarized light emission from these structures or to look at alternative semiconductors and fresh device approaches. © 2007 IEEE.
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