We present the electrical injection, detection, and magnetic field modulation of lateral diffusive spin transport through silicon using surface contacts. Fe∕Al2O3 tunnel barrier contacts are used to create and analyze the flow of pure spin current in a silicon transport channel. Nonlocal detection techniques show that the spin current detected after transport through the silicon is sensitive to the relative orientation of the magnetization of the injecting and detecting contacts. Hanle effect measurements demonstrate that the spin current can be modulated by a perpendicular magnetic field, which causes the spin to precess and dephase in the transport channel.
Above room temperature ferromagnetic behavior is achieved in Si through Mn ion implantation. Threehundred-keV Mn + ions were implanted to 0.1% and 0.8% peak atomic concentrations, yielding a saturation magnetization of 0.3 emu/ g at 300 K for the highest concentration as measured using a SQUID magnetometer. The saturation magnetization increased by ϳ2ϫ after annealing at 800°C for 5 min. The Curie temperature for all samples was found to be greater than 400 K. A significant difference in the temperature-dependent remnant magnetization between the implanted p-type and n-type Si is observed, giving strong evidence that a Si-based diluted magnetic semiconductor can be achieved.
The transport Hanle effect is commonly used to determine spin lifetimes in spin-polarized transport structures. We show that the domain structure of ferromagnetic contacts used to inject and detect the spin current introduces asymmetries to the Hanle lineshape. In addition, the nuclear spin polarization can produce anomalous narrowing and broadening of the Hanle linewidth depending upon the orientation of the transport spin and the applied field. Neither effect is included in the analysis typically applied. We illustrate how these contributions can significantly impact the apparent spin lifetime extracted from the transport Hanle lineshape, and how they can be compensated for.
Abstract-We demonstrate that information can be transmitted and processed with pure spin currents in silicon. Fe/ Al2O3 tunnel barrier contacts are used to produce significant electron spin polarization in the silicon, generating a spin current which flows outside of the charge current path. The spin orientation of this pure spin current is controlled in one of three ways: (a) by switching the magnetization of the Fe contact, (b) by changing the polarity of the bias on the Fe/Al2O3 "injector" contact, which enables the generation of either majority or minority spin populations in the Si, providing a way to electrically manipulate the injected spin orientation without changing the magnetization of the contact itself, and (c) by inducing spin precession through application of a small perpendicular magnetic field. Spin polarization by electrical extraction is as effective as that achieved by the more common electrical spin injection. The output characteristics of a planar silicon three terminal device are very similar to those of nonvolatile giant magnetoresistance metal spin-valve structures.
Mn-implanted Si was investigated using transmission electron microscopy to gain insight into the structure of the implanted region. Diffraction contrast images, selected area diffraction patterns, and high resolution images of the samples were acquired before and after postimplant annealing at 800°C. The images of the annealed samples revealed the formation of nanometer size precipitates distributed throughout the implanted region. Analysis of the selected area diffraction pattern determined that the most prominent lattice spacing of the crystallites is 2.15Å. This spacing indicates that the most probable phase of the crystallites is MnSi1.7 and this is consistent with the Mn:Si binary phase diagram. This phase is paramagnetic at room temperature with a Curie temperature of 47K and cannot readily account for the high Curie temperature of the material.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.