The spin-reorientation transition of thin Au/Co/Au films, grown in-situ on W(110), is studied in XMCD and EXAFS experiments. At 300 K, for in-situ grown Co on a Au(111) film, the dominant easy magnetization direction was found to be in the surface plane, for the uncapped Co/Au bilayers. This is a novel observation, in terms of easy magnetization direction for low thickness Co on Au. After capping with Au, a sizeable out-of-plane magnetization is observed below a thickness of four atomic Co layers. When the spin-reorientation transition occurs because of Au capping, a 5 Å thin Co layer undergoes structural changes of lattice parameters Δa/a = −1.2 % and Δc/c = +6.6 %. The observation of structural changes which accompany the spin reorientation transition, contradicts previous work on Co/Au(111), and allows to quantify the magnetoelastic energy contribution, connected with the presence of the Co/Au interface.

poly(glycidyl methacrylate). The PSA films were prepared with solution casting on pre-cleaned glass surfaces. From a naive point of view, one would have expected homogenous films which are characterized by the average monomer composition. To investigate the surface structure, we probed the density profile perpendicular to the PSA surface using x-ray reflectivity (XRR). We detected the presence of an enrichment layer of one type of monomer at the surface, followed by an enrichment of the other monomer type underneath. Which type of monomer of the statistical copolymer is enriched at the free surface depends on the choice of the minority component. The lateral structure of the detected enrichment layers is probed with grazing incidence small angle x-ray scattering (GISAXS).

For the solid solution system Zn2-2x(CuIn)(x)S-2 XRD measurements revealed an increase of the cell volume as a function of alloying parameter x, but did not provide selective information about the geometric structure. Therefore, EXAFS measurements were performed on thin films of Zn2-2x(CuIn)(x)S-2 at the K shells of the metal ions In, Cu and Zn. Three bond lengths corresponding to the nearest neighbour metal-sulfur distances were identified. These bond lengths remain nearly constant over the whole composition range of the solid solution system. This phenomenon, already known for binary compounds, is now observed for the first time a ternary system as well.The information gained by EXAFS was combined with electronic structure calculations to understand the highly nonlinear dependence of the band gap on x observed in the composition range 0 less than or equal to x less than or equal to 0.25.

The microstructure of undoped cubic and hexagonal GaN films is studied using temperature dependent Ga K-edge EXAFS measurements (10K-290K). The microstructure around the Ga atom is distorted due to a splitting of the second nearest neighbor shell, which consists of Ga atoms. This splitting results in an additional Ga path at a distance longer than expected by 0.8+/-0.05 A and is attributed to local lattice relaxation around nitrogen vacancies. From the temperature dependence of the DW factors for the 2(nd) nearest neighbor shell of Ga, the Einstein temperature is equal to 318+/-25K.

The properties of buried stoichiometric Si3N4 layers are studied using Extended X-ray Absorption Fine Structure (EXAFS), Near-Edge X-ray Absorption Fine Structure (NEXAFS), Infrared Absorption (IR), Nuclear Reaction Analysis (NRA) and Cross-Section Transmission Electron Microscopy (XTEM). The samples were fabricated with ion-implantation using 200 keV 15N ions and a fluency of 1.4 × 1018 at./cm2 and they were characterized in the as-grown state and after annealing. The NSi ratio, measured with NRA, is 1.33, which corresponds to stoichiometric nitrides. Analysis of the EXAFS spectra measured at the N-K-edge indicate that the samples are stoichiometric to a microscopic scale, i.e. the bond lengths and coordination numbers in the 1st and 2nd nearest-neighbor shells are identical to those of a stoichiometric nitride. After annealing at 1200°C for 2 h the α-Si3N4 phase is formed, as detected by IR absorption measurements, while the small concentration of N-dangling bonds, present in the as-implanted state, are completely annealed out, as indicated by the NEXAFS spectra. However, the EXAFS results do not indicate any change in the microstructure of the film. Finally, TEM observations confirm the formation of a nitride layer and reveal the presence of a heavily damaged region in the back interface with the underlying Si layer.

Abstract We performed SEXAFS and core level photoemission studies of Na adsorbed on c(2 × 8)-Ge(111) surface at different coverage regimes. The c(2 × 8) LEED pattern of the clean Ge(111) surface changes to a (1 × 1) with higher background after Na adsorption. A plasmon feature appears on the low energy side of Na 2p core level which indicates metallization of the Na overlayer. We determined the NaGe bond length from the SEXAFS data using the theoretical phase shift of NaGe, calculated by FEFF program. SEXAFS model calculations show that Na atoms are adsorbed on threefold-coordinated hollow sites with a NaGe bond length of 2.9 A and a second nearest neighbour distance of 3.4 A to the Ge atoms in the second layer.

Na intercalated 2H and 1T polytypes of TaS2 have been studied by extended X-ray absorption fine-structure (EXAFS) experiments. The intercalated compounds were prepared by in situ evaporation of Na to the (0001) cleaved surface of the TaS2 crystal. The EXAFS analysis shows that intercalated sodium atoms are positioned in the van der Waals gap in a sixfold coordinated site, giving rise to an increase of the gap width by 1.3 +/- 0.06 Angstrom far the 2H polytype and 1.5 +/- 0.06 Angstrom for the 1T polytype. The corresponding Na-S nearest neighbour distances are 2.85 +/- 0.05 and 2.95 +/- 0.05 Angstrom, respectively. With an increasing amount of deposited Na, a fraction of sodium atoms remains on the surface. The adsorbed Na atoms occupy a threefold hollow site on the surface with a Na-S bond length of 2.80 +/- 0.05 Angstrom for the 2H polytype and 2.91 +/- 0.05 Angstrom for the 1T polytype.

Na deposited 1T and 2H polytypes of TaS2 have been investigated by means of surface extended X-ray absorption fine-structure (SEXAFS) and photoemission studies. The photoemission spectra show that at room temperature Na mainly intercalates for both polytypes with no reactive component. The intercalated sodium atoms are positioned in the van der Waals gap in a sixfold coordinated site due to the SEXAFS analysis. The Na-S nearest neighbour distances are 2.95+/-0.05 Angstrom for 1T and 2.85+/-0.05 Angstrom for 2H polytype corresponding to an increase of the gap width by 1.5+/-0.06 and 1.3+/-0.06 Angstrom, respectively. With increasing amount of deposited Na, a fraction of sodium atoms remains on the surface. The adsorbed Na atoms occupy a threefold hollow site on the surface with a Na-S bond length of 2.91+/-0.05 Angstrom for 1T and 2.80+/-0.05 Angstrom for 2H polytype.