Spin-dependent low-energy 4He+ ion scattering from nonmagnetic surfaces.

We investigated electron-spin-polarized (4)He(+) ion scattering on various nonmagnetic surfaces at kinetic energies below 2 keV. It was observed that the scattered He(+) ion yield depends on the He(+) ion spin. We interpret this spin-dependent scattering in terms of the spin-orbit coupling that acts transiently on the He(+)1s electron spin in the He(+)-target binary collision. This interpretation qualitatively explains the relationship between the spin-dependent scattering and the scattering geometry, incident velocity, and magnetic field arrangement. This is the first study to report spin-orbit coupling caused by projectile electron spin in ion scattering.

Microstrip structures of ZnO nanoparticle aggregates of millimetric length formed by selected-area ion implantation and thermal oxidation.

Regularly arrayed microstrip regions of width approximately 1.4 microm and length extending up to approximately 5 mm, consisting of ZnO nanoparticles (NPs) of diameter approximately 50 nm, were fabricated on silica substrates by a two-step process: i.e., selected-area ion implantation and thermal oxidation. The implantation of 60 keV Zn ions in periodic microstrip regions via a resist mask generated periodic grooves with large wings on the surface of silica glass, which can be ascribed to the radiation-induced plastic deformation of silica and sputtering loss. This is the lowest record of the electronic energy loss (S(e)) value to induce the radiation-induced plastic deformation of silica, while no or very low threshold energy has been predicted from a recent study. After thermal oxidation at 700 degrees C for 1 h, the groove structures with the wings disappeared, and periodic microstrips of ZnO nanoparticle aggregates up to 5 mm long appeared on the surface of the substrate. A clear free-exciton peak due to ZnO NPs is observed from these microstrip structures both in optical absorption and photoluminescence spectra.

Surface phonon dispersion of [Formula: see text].

Surface phonon dispersion of [Formula: see text]-B was measured using high resolution electron energy loss spectroscopy. With adsorption of excess boron, an ordered structure of [Formula: see text] is found at the B coverage of about 0.8 ML. Another structure of 4 × 4 appears mixed with the [Formula: see text] phase at a higher coverage. Using the phonon dispersion relations, the [Formula: see text] structure is inferred to consist of a planar boron network, as in the bulk. In contrast to the NbB(2)(0001) case, no surface core level shift of B 1s is observed on this [Formula: see text] surface, suggesting that the planar boron is not outermost.

Self-assembly prismatic aggregates formed during the calcination of ZnO powders: in situ monitoring by ETA technique and their photocatalytic properties.

This paper describes a unique phenomenon occurred during the calcination of ZnO powders, i.e., the ZnO particles self-assembled to form prismatic aggregates with a clear edges and faces. Field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) were used to characterize the particle morphology and crystal structure of the calcined sample. The emanation thermal analysis (ETA) technique was used to monitor the changes of ZnO particle surface and subsurface microstructure irregularities and the occurrence of interparticle compaction phenomena under in situ conditions of heating and cooling. It was assumed from the ETA results that the driven force of the self-assembly of ZnO particles towards prismatic aggregates originated from the solid state diffusion and migration of grain boundaries. The photocatalytic tests indicated that the prismatic aggregates of ZnO calcined at 800 degrees C demonstrated a highest photocatalytic activity for acetaldehyde decomposition because of the enhancement of the surface-exposed high-active crystal face of (101 0).