To develop silicon-based spintronic devices, we have explored high-quality ferromagnetic Fe3Si/silicon (Si) structures. Using low-temperature molecular beam epitaxy at 130 • C, we realize epitaxial growth of ferromagnetic Fe3Si layers on Si (111) with keeping an abrupt interface, and the grown Fe3Si layer has the ordered DO3 phase. Measurements of magnetic and electrical properties for the Fe3Si/Si(111) yield a magnetic moment of ∼ 3.16 µB/f.u. at room temperature and a rectifying Schottky-diode behavior with the ideality factor of ∼ 1.08, respectively. PACS numbers:Semiconductor spintronic devices such as spin-field effect transistors (spin FET) are one of the possible candidates to substitute for existing silicon-based complementary metal-oxide-semiconductor devices. [1,2,3,4] To realize operations of the spin FET, an electrical spin injection from ferromagnets into semiconductors is an essential technology. For III-V semiconductor devices, several groups have demonstrated highly efficient spin injection and detection using an epitaxial Fe thin film and tailored Schottky tunnel barriers so far. [5,6,7] From these facts, it is necessary for semiconductor spintronics to develop crystal growth techniques of ferromagnets on semiconductors with keeping high-quality interfaces. In particular, it will become key to build epitaxial growth of ferromagnets on silicon (Si) from the viewpoint of application to existing silicon large-scale integrated circuit (LSI) technologies. [8] Moreover, for spintronics, Si has been regarded as an ideal material because of a long spin relaxation time due to weak spin-orbit interaction, weak hyperfine interaction and lattice inversion symmetry, which will give rise to a long spin diffusion length in the devices. Recently, spin transport in Si conduction channels was experimentally demonstrated although their operations were limited at low temperatures. [9,10,11] This means that the spin degree of freedom can be introduced into Si-based electronic devices.To date, ferromagnetic MnAs thin films have been grown epitaxially on Si (001), [12] but electrical spin injection from MnAs into Si across a Schottky tunnel barrier has never been demonstrated unfortunately. Also, the Curie temperature of MnAs is ∼ 315 K, [13] which may be relatively low for an operation temperature of future LSIs. Thus, possibilities of other high-Curie temperature materials compatible with Si should be explored. Here we select a ferromagnetic Heusler alloy Fe 3 Si thin film, which has a high Curie temperature above 800 K, a relatively high spin polarization of ∼ 45 % and a small coercive field of ∼ 7.5 Oe. [14] In this letter, we achieve highly

We demonstrate electrical injection and detection of spin-polarized electrons in silicon (Si) using epitaxially grown Fe3Si/Si Schottky-tunnel-barrier contacts. By an insertion of a δ-doped n + -Si layer (∼ 10 19 cm −3 ) near the interface between a ferromagnetic Fe3Si contact and a Si channel (∼ 10 15 cm −3 ), we achieve a marked enhancement in the tunnel conductance for reverse-bias characteristics of the Fe3Si/Si Schottky diodes. Using laterally fabricated four-probe geometries with the modified Fe3Si/Si contacts, we detect nonlocal output signals which originate from the spin accumulation in a Si channel at low temperatures. PACS numbers:To solve critical issues caused by the scaling limit of complementary metal-oxide-semiconductor (CMOS) technologies, spin-based electronics (spintronics) has been studied.[1] For semiconductor spintronic applications, an electrical spin injection from a ferromagnet (FM) into a semiconductor (SC) and its detection are crucial techniques.Recently, methods for spin injection and/or detection in silicon (Si) were explored intensely [2,3,4,5,6,7] because Si has a long spin relaxation time and is compatible with the current industrial semiconductor technologies. Although electrical detections of spin transport in Si conduction channels were demonstrated by two research groups, [4,5] an insulating Al 2 O 3 tunnel barrier between FM and Si was utilized for efficient spin injection and/or detection. To realize gate-tunable spin devices, e.g., spin metal-oxidesemiconductor field effect transistors (spin MOSFET), [8] demonstrations of electrical spin injection and detection in Si conduction channels using Schottky tunnel-barrier contacts will become considerably important. [9,10] By low-temperature molecular beam epitaxy (LTMBE), we recently demonstrated highly epitaxial growth of a binary Heusler alloy Fe 3 Si on Si and obtained an atomically abrupt heterointerface. [11] In this letter, inserting a heavily doped n + -Si layer near the abrupt interface between Fe 3 Si and n-Si, we achieve an effective Shottky tunnel barrier for spin injection into Si. Using nonlocal signal measurements, we demonstrate electrical injection and detection of spin-polarized electrons in Si conduction channels though the Schottky-tunnel-barrier contacts.The n + -Si layer was formed on n-Si(111) (n ∼ 4.5 × 10 15 cm −3 ) by a combination of the Si solid-phase epitaxy with an Sb δ-doping process, [12] where the carrier * E-mail: hamaya@ed.kyushu-u.ac.jp † E-mail: miyao@ed.kyushu-u.ac.jp concentration of the n + -Si layer was ∼ 2.3 × 10 19 cm −3 , determined by Hall effect measurements, and ∼ 10-nmthick non-doped Si layer was grown on the Sb δ-doped layer. Ferromagnetic Fe 3 Si layers with a thickness of ∼ 50 nm were grown by LTMBE at 130 • C, as shown in our previous work.[11] The interface between Fe 3 Si and n + -Si was comparable to that shown in Ref. 11. To evaluate electrical properties of the Fe 3 Si/Si Schottky contacts, we firstly fabricated two different Schottky diodes (∼ 1 mm in diameter) with and w...

The peripheral nerve of experimental diabetic neuropathy (EDN) is reported to be ischemic and hypoxic, with an increased dependence on anaerobic metabolism, requiring increased energy substrate stores. When glucose stores become reduced, fiber degeneration has been reported. We evaluated glucose uptake, nerve energy metabolism, the polyol pathway, and protein kinase C (PKC) activity in EDN induced by streptozotocin. Control and diabetic rats received lipoic acid (0, 10, 25, 50, 100 mg/kg). Duration of diabetes was 1 month, and alpha-lipoic acid was administered intraperitoneally 5 times per week for the final week of the experiment. Nerve glucose uptake was reduced to 60, s 37, and 30% of control values in the sciatic nerve, L5 dorsal root ganglion, and superior cervical ganglion (SCG), respectively, in rats with EDN. Alpha-lipoic acid supplementation had no effect on glucose uptake in normal nerves at any dose, but reversed the deficit in EDN, with a threshold between 10 and 25 mg/kg. Endoneurial glucose, fructose, sorbitol, and myo-inositol were measured in sciatic nerve. Alpha-lipoic acid had no significant effect on either energy metabolism or polyol pathway of normal nerves. In EDN, endoneurial glucose, fructose, and sorbitol were significantly increased, while myo-inositol was significantly reduced. Alpha-lipoic acid had a biphasic effect: it dose-dependently increased fructose, glucose, and sorbitol, peaking at 25 mg/kg, and then fell beyond that dose, and it dose-dependently increased myo-inositol. Sciatic nerve cytosolic PKC was increased in EDN. ATP, creatine phosphate, and lactate were measured in sciatic nerve and SCG. Alpha-lipoic acid prevented the reduction in SCG creatine phosphate. We conclude that glucose uptake is reduced in EDN and that this deficit is dose-dependently reversed by alpha-lipoic acid, a change associated with an improvement in peripheral nerve function.

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