The generation of spin-polarized electrons at room temperature is an essential step in developing semiconductor spintronic applications. To this end, we studied the electronic states of a Ge(111) surface, covered with a lead monolayer at a fractional coverage of 4/3, by angle-resolved photoelectron spectroscopy (ARPES), spin-resolved ARPES and first-principles electronic structure calculation. We demonstrate that a metallic surface-state band with a dominant Pb 6p character exhibits a large Rashba spin splitting of 200 meV and an effective mass of 0.028 m_e at the Fermi level. This finding provides a material basis for the novel field of spin transport/accumulation on semiconductor surfaces. Charge density analysis of the surface state indicated that large spin splitting was induced by asymmetric charge distribution in close proximity to the nuclei of Pb atoms.

The dynamics of water dimers was investigated at the single-molecule level by using a scanning tunneling microscope. The two molecules in a water dimer, bound on a Cu(110) surface at 6 K, were observed to exchange their roles as hydrogen-bond donor and acceptor via hydrogen-bond rearrangement. The interchange rate is $\sim 60$ times higher for $({\mathrm{H}}_2\mathrm{O}{)}_2$ than for $({\mathrm{D}}_2\mathrm{O}{)}_2$, suggesting that quantum tunneling is involved in the process. The interchange rate is enhanced upon excitation of the intermolecular mode that correlates with the reaction coordinate.

We report a novel structure of water aggregate by means of scanning tunneling microscopy. Water molecules are self-assembled into one-dimensional chains on Cu(110) at 78 K. The chain exhibits a zigzag structure with a period of 7.2 Å and grows to a length of $\sim 1000\AA$. We propose that water hexamers are arranged alternately along the chain. Interchain repulsion due to dipole interaction facilitates the 1D chain growth. A two-dimensional overlayer develops only at high coverage.

We have found a large spin splitting due to the Rashba spin-orbit interaction on the $\text{Bi}/\text{Ge}\left(111\right)\text{−}\left(\sqrt{3}\times \sqrt{3}\right)R30°$ surface by using angle-resolved photoelectron spectroscopy and first-principles electronic structure calculation. A surface resonance band derived from Bi exhibits the Rashba spin splitting with a large Rashba parameter $\left({\alpha }_R\right)$ of $1.8\text{eV}\text{Å}$. The spin-split states have a considerable $6s\text{−}6p_z$ hybridized character, which leads to a strong perpendicular asymmetry of the charge density in close proximity of Bi nuclei. The result suggests that the magnitude of the Rashba splitting on Bi-adsorbed surfaces should depend crucially on the local-bonding geometry of Bi.