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Interface mixing in [Fe/Cr/Al]x10 multilayer is studied under 120 MeV Ag9+swift heavy ions (SHIs) irradiation. The multilayers with different thicknesses were deposited using electron beam evaporation technique. The SHIs induced modifications in structural and magnetic properties were examined with X-ray reflectivity (XRR), magneto-optic Kerr effect (MOKE), and X-ray absorption fine structure (XAFS) to reveal interface diffusivity, including variation in magnetic coercivity, in-plane anisotropy, and local structure. The height of 1st order Bragg peak of XRR is used to determine the diffusion length as a function of ion fluence, and it is evident that the lower thickness of [Fe/Cr/Al]x10 multilayer possesses higher interface mixing as compared to samples with higher thickness. MOKE results confirm that both multilayers are soft magnetic in nature and show different behavior of in-plane anisotropy. With the SHIs irradiation, coercivity exhibits opposite trends for different thicknesses of Fe/Cr/Al multilayers due to different interface mixing. Fe K-edge XAFS is used for quantitative analysis of the Fe-Cr and Fe-Al phases as a function of multilayer thickness and ion fluence. The inelastic thermal spike (i-TS) model with size effect is used to explain the observed thickness-dependent intermixing due to the SHIs irradiation. The lattice temperature evaluation calculated by i-TS model shows longer spike duration in thinner film resulting in higher mixing.

X-ray reflectivity and spectroscopy, voltammetry, and scanning probe microscopy were used to investigate the dealloying of CuxAu (with x ≈ 4) below the critical potential. We studied ultrathin films deposited on oxidized silicon wafers with a thickness of 2.2, 8.5, and 43 nm, which had been determined precisely by X-ray reflectivity. With the help of quantitative X-ray fluorescence (XRF) analysis, the average composition of the films before and after the leaching was determined. In this way, the amount of material going into solution could precisely be analyzed. A compositional depth profile was obtained by angle-dependent hard X-ray photoelectron spectroscopy before and after the dealloying. Two novel findings are reported. (1) Close to the Cu/Cu2+ redox potential, a pronounced increase in current is observed in the voltammogram. While this charge transfer seems to indicate the dissolution of Cu2+, XRF analysis proves that no copper has been lost to the solution. (2) The XRF analysis shows that some gold...

DAE SOLID STATE PHYSICS SYMPOSIUM 2017, Mumbai, India, 26 Dec 2017 - 30 Dec 2017; AIP conference proceedings 1942, 080057 (2018). doi:10.1063/1.5028891, The present work describes the design and performance of a vacuum compatible portable mini chamber for temperature dependent GISAXS and GIWAXS studies of thin films and multilayer structures. The water cooled body of the chamber allows sample annealing up to 900 K using ultra high vacuum compatible (UHV) pyrolytic boron nitride heater, thus making it possible to study the temperature dependent evolution of structure and morphology of two-dimensional nanostructured materials. Due to its light weight and small size, the chamber is portable and can be accommodated at synchrotron facilities worldwide. A systematic illustration of the versatility of the chamber has been demonstrated at beamline P03, PETRA-III, DESY, Hamburg, Germany. Temperature dependent grazing incidence small angle x-ray scattering (GISAXS) and grazing incidence wide angle x-ray scattering (GIWAXS) measurements were performed on oblique angle deposited Co/Ag multilayer structure, which jointly revealed that the surface diffusion in Co columns in Co/Ag multilayer enhances by increasing temperature from RT to ∼573 K. This results in a morphology change from columnar tilted structure to densely packed morphological isotropic multilayer, Published by AIP Publishing LLC, Melville, NY

We studied pristine and leached ultra-thin Cu x Au ( x ≈ 4) films by hard X-ray photoelectron spectroscopy. The Au 4 f and Cu 3 s core levels show a shift in binding energy which is opposite to expected from the nobility of the elements, which is explained by charge transfer involving differently screening s and d valence levels of the elements [W. Eberhardt, S.C. Wu, R. Garrett, D. Sondericker, F. Jona, Phys. Rev. B 31 (1985) 8285]. The magnitude of the chemical shifts of the metal lines is strongly influenced by the finite size and disorder of the films. Angular dependent photoelectron emission allowed to assess the alloy composition as a function of depth larger than 5 nm. The potential controlled dealloying proceeds into depth like a spinodal decomposition with Cu going into solution and the remaining Au accumulating in the surface region. The compositional gradient did not lead to a significant broadening of the metal photoelectron lines suggesting a non-local screening mechanism.

Generation of self organized nanoripple patterns on Si (100) single crystal surface using low energy Ar ion beam erosion has been studied. Ion energy and ion fluence dependence of the ripple pattern is in general agreement with the reported works. However, it is found that at relatively low fluences, the pattern formation depends upon the direction of the projection of the ion beam on Si surface with respect to its crystallographic orientation. Ripple formation is facilitated if the projection of ion beam on the sample surface is along (010) direction as against (011) direction. For higher ion fluence, when the Si surface layer is fully amorphized, pattern formation is independent of the azimuthal direction of the ion beam. Copyright © 2013 VBRI press.

This article describes the development of a soft x-ray beamline on a bending magnet source of Indus-2 storage ring (2.5 GeV) and some preliminary results of x-ray absorption spectroscopy (XAS) measurements using the same. The beamline layout is based on a spherical grating monochromator. The beamline is able to accept synchrotron radiation from the bending magnet port BL-1 of the Indus-2 ring with a wide solid angle. The large horizontal and vertical angular acceptance contributes to high photon flux and selective polarization respectively. The complete beamline is tested for ultrahigh vacuum (UHV) ∼ 10−10 mbar. First absorption spectrum was obtained on HOPG graphite foil. Our performance test indicates that modest resolving power has been achieved with adequate photon flux to carry out various absorption experiments.

W/Si multilayers with B4C as a diffusion barrier were deposited using ion beam sputtering technique. It was found that incorporation of B4C at both interfaces of Si enhances the reflectivity of the multilayer. Though the interface of W/Si or W/B4C has been studied in literature, what happens at Si/B4C interfaces is largely unknown. This is primarily due to absence of contrast between Si/B4C for x‐rays. For neutrons there is significant contrast between Si and B4C, therefore we used neutron reflectivity to study thermal stability of Si/B4C multilayers. It was found that up to an annealing temperature of 573 K, the multilayer remains intact however at higher temperature interdiffusion starts.

Intermixing induced in W/Si multilayers by irradiation with 150 MeV Ag+ ions has been studied. In situ x-ray reflectivity measurements during heavy ion irradiation allows one to monitor the evolution of interface mixing as well as internal stresses as a function of time during irradiation. The technique of x-ray reflectivity is sensitive enough to measure diffusion length down to 0.1 nm. A finite intermixing occurs in the system, in spite of it having a positive heat of mixing. High accuracy of the technique allows one to discern subtle effects of factors like stress or film thickness, on swift heavy ion irradiation induced intermixing. The measurements provide clear evidence of an enhanced intermixing in the presence of tensile stress in the film. Mixing efficiency decreases with increasing film thickness. The film thickness dependence of mixing efficiency can be understood in terms of the thermal spike model by taking into consideration the changes in electron mobility due to scattering from surface and interfaces.

The Ni/V multilayers are useful as soft x-ray mirrors, polarizers, and phase retarders. For these applications, it is necessary that the interfaces roughness and interdiffusion must be as small as possible. The V-on-Ni and Ni-on-V interfaces are asymmetric due to the difference in the surface free energy of Ni and V. In this work, we report Ag surfactant mediated growth of Ni/V superlattices prepared using ion beam sputter deposition technique. These superlattices were studied using x-ray and neutron scattering techniques. It was found that when added in an optimum amount, Ag surfactant results in reduced interface roughness and interdiffusion across the interfaces. Obtained results can be understood with the surfactant floating-off mechanism leading to a balance in the surface free energy of Ni and V.

Crystalline tungsten oxide thin films are obtained by thermal oxidation of metallic W films, deposited on quartz substrates under vacuum conditions by the pulsed laser deposition (PLD) technique. The as-deposited tungsten films are annealed in air at various temperatures, viz. 673, 873 and 1073 K. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and micro-Raman techniques are employed for the investigation of microstructural characterization of both as-deposited and annealed films. The influence of laser energy and duration of deposition on the microstructural, optical and electrical properties of the films are studied in detail. Among the films investigated, thicker tungsten films (having a thickness of ~500 nm), deposited with laser fluence 4 J cm−2 for 45 min duration and annealed at 873 K, exhibit better physical properties and microstructural features compared to other films.

Nitrogen incorporated tungsten oxide films are deposited on heated quartz substrates (973 K) for various nitrogen background pressures (namely, pN2 = 0.04, 0.08, 0.12, 0.17 and 0.20 mbar) by the pulsed laser deposition technique. The prepared films are characterized by using techniques such as x-ray diffraction (XRD), energy dispersive x-ray spectroscopy (EDX), atomic force microscopy (AFM), scanning electron microscopy, micro-Raman spectroscopy, UV–visible spectroscopy and temperature dependent dc electrical resistivity studies. XRD measurements revealed the presence of tungsten sub-oxide and WO3 phases depending on the nitrogen ambient pressure. Nitrogen incorporation in the films is confirmed through EDX analysis. Morphological features consisting of densely packed, void-free grains with a distinct grain boundary are portrayed through the AFM images of the films. The WO3 lattice distortion due to nitrogen incorporation is discussed using micro-Raman spectra of the films. Band gap narrowing, moderate transmittance in the visible range and the very low resistivity exhibited by the films prepared at pN2 = 0.12 mbar are imperative as far as solar cell applications are considered. A comparably higher visible transmittance with a band gap of 3.141 eV and a low resistivity obtained for the N : WO3 films prepared at a nitrogen ambient of 0.17 mbar is among the best reported for the coexistence of transparency in the visible range and conductivity in tungsten oxide films, which make them significant for micro-electronic applications.

The effect of 120 MeV Au9+ ion irradiation and thermal annealing on [W(25 A)∕Ni(25 A)]×10 multilayers, grown on float-glass and silicon substrates, has been studied. Wide-angle x-ray diffraction studies of pristine, as well as irradiated W/Ni multilayers, show deterioration of the superlattice structure, but x-ray reflectivity (XRR) studies reveal a nearly unaffected multilayer structure. Analysis of the XRR data using “Parratt’s formalism” does show a significant increase of W/Ni interface roughness. The observed differences in wide-angle and low-angle scattering results of the irradiated W/Ni multilayers suggest significant difference in the interlayer and intralayer mixing induced by swift heavy ion irradiation. XRR results also reveal the fluence dependence of layer densification. Plane, as well as cross-sectional transmission electron microscopy, carried out in imaging and diffraction modes very clearly shows that at higher fluence the intralayer microstructure becomes nanocrystalline (1–2 nm) and at...