Using ferromagnetic metal / silicon dioxide contacts on silicon, NRL scientists Connie Li, Olaf van 't Erve and Jonker electrically generate and detect spin accumulation and precession in the silicon transport channel at temperatures up to 225˚C, and conclude that the spin information can be transported in the silicon over distances readily compatible with existing fabrication technology. They thus overcome a major obstacle in achieving control of the spin variable at temperatures required for practical applications in the most widely utilized semiconductor.
To make a semiconductor spintronic device, one needs contacts that can both generate a current of spin-polarized electrons (called a spin injector), and detect the spin polarization of the electrons (spin detector) in the semiconductor. Because the magnetic contact interface is likely to introduce additional scattering and spin relaxation mechanisms not present in the silicon bulk, the region of the semiconductor directly beneath the contact is expected to be a critical factor in the development of any future spin technology. The NRL scientists probe the spin environment directly under the magnetic metal / silicon dioxide contact using the three terminal geometry illustrated in the accompanying figure. Demonstration of spin precession and dephasing in a magnetic field transverse to the injected spin orientation, known as the Hanle effect, is conclusive evidence of spin accumulation, and enables a direct measure of the spin lifetime, a critical parameter for device operation. The NRL researchers observed Hanle precession of the electron spin accumulation in the silicon channel under the contact for biase
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Naval Research Laboratory