We demonstrate electrical injection and detection of spin-polarized electrons in silicon (Si) using epitaxially grown ${\text{Fe}}_3\text{Si}/\text{Si}$ Schottky-tunnel-barrier contacts. By an insertion of a $\delta$ -doped $n^{+}\text{-Si}$ layer $\left(\sim {10}^{19}{\text{cm}}^{-3}\right)$ near the interface between a ferromagnetic ${\text{Fe}}_3\text{Si}$ contact and a Si channel $\left(\sim {10}^{15}{\text{cm}}^{-3}\right)$ , we achieve a marked enhancement in the tunnel conductance for reverse-bias characteristics of the ${\text{Fe}}_3\text{Si}/\text{Si}$ Schottky diodes. Using laterally fabricated four-probe geometries with the modified ${\text{Fe}}_3\text{Si}/\text{Si}$ contacts, we detect nonlocal output signals that originate from the spin accumulation in a Si channel at low temperatures.

Orientation-controlled Si films on transparent insulating substrates are strongly desired to achieve high-efficiency thin-film solar cells. We have developed the interfacial-oxide layer modulated Al-induced low temperature $\left(<450°\text{C}\right)$ crystallization technique, which enables dominantly (001) or (111)-oriented Si films with large grains $\left(20–100\mu \text{m}\right)$ . These results are qualitatively explained on the basis of a model considering the phase transition of the interfacial Al oxide layers. This process provides the orientation-controlled Si templates on insulating substrates, which enables successive high quality epitaxial growth necessary for advanced Si thin-film solar cells.

Poly-Ge thin-film transistors (TFTs) with Schottky source/drain (S/D) contacts were fabricated on glass by low-temperature $(<500°\mathrm{C})$ processing. First, the annealing characteristics of Ni/crystal-Ge stacked structures were examined. The results indicated that $\mathrm{Ni}\mathrm{Ge}∕n\text{-}\mathrm{Ge}$ Schottky contacts (${\varphi }_{B_n}=0.51\mathrm{eV}$ , $n=1$ ) with flat interfaces and low reverse leakage current $[(2–5)\times {10}^{-2}\mathrm{A}∕{\mathrm{cm}}^2]$ could be obtained by choosing an appropriate annealing temperature $(200–300°\mathrm{C})$ . Based on this result, $p$ -channel TFTs were fabricated with poly-Ge formed on glass by solid-phase crystallization at $500°\mathrm{C}$ . TFTs showed relatively high hole mobility (about $140{\mathrm{cm}}^2∕\mathrm{V}\mathrm{s}$ ) with very low S/D parasitic resistance and no kink effect. The potential capability of the proposed devices for high-performance TFTs was demonstrated.

To develop silicon-based spintronic devices, we have explored high-quality ferromagnetic ${\mathrm{Fe}}_3\mathrm{Si}$ /silicon (Si) structures. Using low-temperature molecular beam epitaxy at $130°\mathrm{C}$ , we realize the epitaxial growth of ferromagnetic ${\mathrm{Fe}}_3\mathrm{Si}$ layers on Si(111) with an abrupt interface, and the grown ${\mathrm{Fe}}_3\mathrm{Si}$ layer has the ordered $D{O}_3$ phase. Measurements of magnetic and electrical properties for the ${\mathrm{Fe}}_3\mathrm{Si}∕\mathrm{Si}\left(111\right)$ yield a magnetic moment of $\sim 3.16{\mu }_B∕\mathrm{f.u.}$ at room temperature and a rectifying Schottky-diode behavior with the ideality factor of $\sim 1.08$ , respectively.

We study electrical properties of metal/Ge contacts with an atomically controlled interface, and compare them with those with a disordered one, where atomically controlled interfaces can be demonstrated by using ${\text{Fe}}_3\text{Si}/\text{Ge}\left(111\right)$ contacts. We find that the Schottky barrier height of ${\text{Fe}}_3\text{Si}/n\text{-Ge}\left(111\right)$ contacts is unexpectedly lower than those induced by the strong Fermi-level pinning at other $\text{metal}/n\text{-Ge}$ contacts. For ${\text{Fe}}_3\text{Si}/p\text{-Ge}\left(111\right)$ contacts, we identify clear rectifying behavior in $I\text{-}V$ characteristics at low temperatures, which is also different from $I\text{-}V$ features due to the strong Fermi-level pinning at other $\text{metal}/p\text{-Ge}$ contacts. These results indicate that there is an extrinsic contribution such as dangling bonds to the Fermi-level pinning effect at the directly connected metal/Ge contacts.