Spin-polarized He+ ion scattering spectroscopy (SP-ISS) study on a polycrystalline Sn target surface is reported. We observed substantial spin dependent He+ ion scattering on the non-magnetic Sn target. It is not due to He+ ion neutralization, but it is attributed to spin–orbit coupling (SOC) that acts transiently on the He+1s1s electron spin in the He+–Sn atom binary collision. We found that the spin dependent scattering quantified as the spin asymmetry exhibits periodic oscillation with the reciprocal of the He+ ion velocity. The oscillation originates from the SOC induced-slight energy difference of the [He+–Sn] and [He0–Sn+] systems which are involved in the quasi-resonant charge transfer. The oscillatory spin asymmetry shows that SOC arises from collision induced intermediate state.

We studied low-energy (1.57 keV) electron-spin polarized 4He+ ion scattering on various 5d transition metal targets. The scattered ion intensity generally differed between the incident He+ ions with up and down spins. This spin dependent ion scattering is attributed to the spin–orbit coupling (SOC) that acts transiently on the He+ 1s electron spin in the He+-target binary collision. We observed that the amplitude of the spin dependence in ion scattering, i.e., the spin asymmetry, differs between 5d transition metal targets. This target element dependence of the spin asymmetry is discussed in terms of re-ionization of He0, which originates from the neutralization of the He+ ion during the He+-target collision. Since the re-ionization is spin independent process, it degrades the effective spin polarization of the He+ ion beam. This explains smaller spin asymmetry with the target on which He0 is re-ionized with higher rate.

•We study surface segregation of W doped in ZnO.•Segregated W occupies a Zn site at the outermost surface of O-face ZnO.•Segregated W is likely hexavalent at the Zn site.We observed surface segregation of W (0.05–4 mol%) doped in ZnO films by annealing above 900 K. The segregation coefficient was related to the crystal quality of the film, where slower segregation occurs in higher-quality crystalline films. Using low-energy He+ ion scattering spectroscopy for structure analysis, we found that the W–ZnO surface terminates with an O-layer, and W is located in a substitutional site of Zn at the second surface layer as a consequence of segregation. On the other hand, we observed no indication that W occupies certain sites in the ZnO lattice at the subsurface. Ultraviolet photoelectron spectroscopy (He I) on the W-segregated ZnO surface indicates that W is hexavalent at the Zn site. The segregation of the W atom is likely accompanied by two Zn vacancies. Ion beam mixing followed by annealing of the ZnO surface deposited with W provides a surface electronic structure similar to that of W-segregated ZnO.

We study the effect of 2 keV Ar+ ion beam irradiation (IBI) on the outermost surface magnetism of an Fe(100) film by spin-polarized ion scattering spectroscopy (SP-ISS). We found that the coercivity of the outermost surface is enhanced with IBI. On the other hand, spin polarization is independent of IBI. These effects of IBI on surface magnetism are discussed in terms of morphology and atomic arrangement of the surface analyzed by ISS and reflection high-energy electron diffraction. The variation of coercivity with respect to the average iron film thickness d followed a power law d− n with the assumption that d is linearly dependent on the IBI time.Research highlights► We study the Fe(100) surface magnetism by spin-polarized ion scattering spectroscopy. ► The coercivity of the outermost surface is enhanced with the ion beam irradiation. ► Spin polarization is independent of the ion beam irradiation. ► These effects are understood in terms of morphology and atomic arrangement of the surface. ► The coercivity followed a power low with respect to the film thickness.

We discuss the validity of surface spin polarization analysis with element selectivity using spin-polarized ion scattering spectroscopy (SP-ISS). We examined the control of the incident 4He+ spins and successfully conducted magnetic hysteresis measurement on an Fe(100) surface. The spin polarization of the Fe(100) surface exposed to O2 atmosphere measured by spin-polarized ion neutralization spectroscopy was consistent with that reported by spin-polarized metastable de-excitation spectroscopy. The element selectivity of SP-ISS is discussed in terms of ion neutralization, re-ionization, and multiple scattering.

The interaction of CCl4 molecules with Fe(0 0 1) surfaces was investigated by spin-polarized ion scattering spectroscopy (SP-ISS). It was observed that CCl4 molecules adsorb dissociatively on the surface at ambient temperature (∼290 K), and consequently, iron and chlorine were major surface constituents. It was found that the chlorine adatoms are located atop of iron atoms of the second surface layer (hollow sites of the surface). It is indicated that the spin state of iron atoms at the surface is not affected by exposure to a CCl4 atmosphere, while almost no spin is induced in the chlorine adatoms. Similar behavior is observed in the spin states of iron and chlorine on an oxygen preadsorbed-Fe(0 0 1) surface. The difference in the spin states of iron and chlorine clarifies the local property of the incidence ion neutralization and element selectivity of SP-ISS in this CCl4/Fe system.

We developed spin-polarized ion scattering spectroscopy (SP-ISS). In SP-ISS, spin-polarized 4He+ ions are projected onto a sample surface, and the kinetic energy of scattered ions, which survive in neutralization, are analyzed. We observed that scattered ion yield depends on spin of the incident He+ ions on an Fe(1 0 0) surface exposed to an oxygen atmosphere. Furthermore, we revealed that the spin dependence of scattered ion yield reflects the spin state of target atoms. Thus, SP-ISS may be capable of analyzing the spin state of outermost surfaces with element selectivity.

Spin polarization of He+ ions in Penning ionization of optically pumped He metastable atoms (He∗(23S1)) has been investigated. It was indicated that radiation trapping is a predominant depolarization effect in the He pressure range below 100 Pa. A drastic drop of He∗ polarization was observed below the He pressure of 10 Pa. The He+ polarization was estimated to be 16.6 ± 3.1% from the spin dependence of the electron spectra obtained on a magnetized sample surface (spin-polarized ion neutralization spectroscopy).

The adsorption structure and spin-resolved electronic structure of pentacene on Fe(1 0 0) surfaces were investigated using elastic recoil detection analysis (ERDA) and spin-polarized metastable deexcitation spectroscopy (SPMDS), respectively. It was found that the pentacene molecule adsorbs with its molecular plane parallel to the surface in the initial stage of growth, while the molecular plane tilted from the surface with the increase of the coverage. In the pentacene–Fe surface interaction, a donation and backdonation interaction was indicated. It was found that the polarity of the spin polarization induced in the pentacene molecular orbitals was opposite to each other between the orbitals contributing to the donation and those contributing to the backdonation.