Notes: A grazing incidence x-ray reflectivity technique has been used to determine electron density profile (EDP) as a function of depth in Nb-on-Si and Si-on-Nb bilayer, Nb–Si–Nb and Si–Nb–Si trilayer, and Nb/Si multilayer structures. In each case, films having layer thicknesses of 35 Å were deposited on float glass and Si(100) substrates under ultrahigh vacuum conditions using an electron beam evaporation technique. EDP determined in as-deposited bilayer films shows that the widths of Si-on-Nb and Nb-on-Si interfaces are 20 and 40 Å, respectively. The large difference observed in the widths is attributed to the different growth morphology of 35 Å Nb and 35 Å Si single layer films as revealed by atomic force microscopy investigations. In situ dc resistance measurements carried out on 35 Å single layer Nb films during growth show percolation at a thickness much less than the layer thickness. In case of as-deposited Nb–Si–Nb trilayer film, EDP shows a width of 21 Å at both the interfaces viz. Si-on-Nb and Nb-on-Si whereas in the case of as-deposited Si–Nb–Si trilayer films, the widths of Si-on-Nb and Nb-on-Si interfaces are 21 and 42 Å, respectively. The EDPs obtained from bilayer and trilayer films are used to determine layer-by-layer electron density variation in Nb/Si multilayer structures. The results corresponding to the as-deposited multilayer structure indicate that interdiffusion is larger in the bottom layers of the stack. To study the role of kinetic and thermodynamic factors in the interfacial reactions, the bilayer, trilayer, and multilayer samples were isochronally annealed in vacuum up to a temperature of 300 °C in steps of 50 °C for 1 h. EDP of annealed bilayer and trilayer films show an increase in interfacial width due to interdiffusion of Nb and Si and samples annealed at 250 and 300 °C show Nb-rich and Si-rich intermixed regions. In addition to this, plateau regions having an electron density of 1.8 e/Å3 are observed in the EDP of Nb–Si–Nb and Si–Nb–Si trilayer structures annealed at 300 °C which indicates the formation of a Nb3Si phase. Structural parameters obtained from EDP are extended to interpret the results in as-deposited and annealed multilayer structures. The observed contraction in a bilayer period of an annealed multilayer structure is interpreted in terms of formation of a dense Nb3Si phase confirmed by wide angle x-ray diffraction measurements. Consequently, the multilayer structure is fully destroyed between 250–300 °C. © 2000 American Institute of Physics.

Notes: The concept of simultaneous use of pulsed laser evaporation and conventional thermal evaporation has been used for the first time to synthesize composite thin-film structures. It is shown that the use of pulsed laser evaporation of α-Fe2O3 concurrently with thermal evaporation of aluminum leads to a composite state defined by the presence of clusters of iron-related material in the aluminum matrix. The microstructural aspects of the physical state of the composite are studied by using conversion electron Mössbauer spectroscopy, glancing angle x-ray diffraction, and scanning electron microscopy.

Notes: Reactive alloying of the Fe-W system under benzene by use of pulsed laser treatment is demonstrated. The as-deposited and processed samples were characterized by employing the techniques of low-angle x-ray diffraction, Rutherford backscattering, conversion electron Mössbauer spectroscopy, and x-ray photoelectron spectroscopy. Formation of ternary phase FeW3C is observed at a lower fluence while its amorphization is observed at a higher fluence.

Notes: Iron oxide and ferrite films were prepared by pulsed ruby laser evaporation from the respective bulk materials on alumina substrates. The variation in the film properties as a function of the substrate temperature and oxygen partial pressure during deposition was studied. Conversion electron Mössbauser spectroscopic analysis showed that the stoichiometry and microstructure of such films depend on these deposition conditions, especially the oxygen partial pressure in the system. Typically it was observed that when laser deposition is performed by vaporizing α-Fe2O3 in the oxygen partial pressure of 10−4 Torr, Fe3O4 thin films were formed while deposition at a background pressure of 10−6 Torr led to formation of FeO films. Similar experiments were also performed on zinc ferrite and it was observed that the nanosecond pulsed evaporation process transports the stoichiometry of metal constituents from the bulk to the film with a small degree of zinc enrichment. In addition to Mössbauer spectroscopy, other techniques such as scanning electron microscopy and x-ray diffraction were also used to characterize the laser-deposited films.

Notes: The oxidation behavior of Fe50Ni50 alloy foils implanted with 80-keV N+2 ions at a dose of ∼1016 ions/cm2 is studied by using the technique of conversion electron Mössbauer spectroscopy (CEMS). The oxidation is carried out in air at various temperatures up to a maximum of 500 °C, for different intervals of time. It is shown that the as-implanted as well as implanted and annealed foils exhibit higher resistance to oxidation as compared to the virgin foils; the oxidation resistance being significantly higher in the case of the annealed foils. It is established that the reason for improvement in oxidation resistance is nickel enrichment of the surface layers leading to formation of diffusion-limiting nickel-rich NixFe3−xO4 phase at the oxide-metal interface during the early oxidation process. The presence of this phase in the oxidized samples is inferred from the hyperfine interactions exhibited by the corresponding CEMS spectra and also from x-ray diffraction measurements.

Notes: The nature of pulsed ruby laser-induced vaporization from the surface of a binary oxide represented by ZnxFe3−xO4 (x∼1) is studied via morphological (scanning electron microscopy), compositional (energy-dispersive analysis of x ray), structural (small-angle x-ray diffraction), and microstructural (conversion electron Mössbauer) examination of the laser-processed surface and correlation of the related surface modification to the properties of thin films deposited therefrom, and subjected to similar examination. Zinc ferrite (ZnxFe3−xO4) films have been deposited on single-crystal Al2O3 substrates and the dependence of the film properties on the oxygen partial pressure and substrate temperature during deposition is studied to explore optimized conditions for deposition of near single-phase stoichiometric films.

Notes: The formation of mixed metastable phases as a result of ion-beam mixing of the Al-Fe-Mn system with 100-keV Ar+ ions and their subsequent transformations upon thermal annealing have been studied. The mixed state is comprised of both binary (Fe-Al, Fe-Mn, Mn-Al) and ternary (Al-Fe-Mn) metastable phases. Conversion-electron Mössbauer spectroscopy and low-angle x-ray diffraction studies reveal the formation of disordered phases upon ion beam mixing, which acts as a precursor for the growth of the equilibrium phases upon thermal annealing via lowering of kinetic barrier for the reactions.

Notes: The influence of 60-keV N+2 ion implantation on the aqueous degradation of the Y1Ba2Cu3O7−x high-Tc superconductor is studied by the small-angle x-ray diffraction technique. Structural depth profiling is performed by registering the x-ray data at several small angles of incidence between 0.3° and 10.0° within Seeman–Bohlin geometry. Examination of samples implanted at a dose value of 3×1017 ions/cm2 and subjected to different aqueous treatments reveals that implantation arrests the degradation process and imparts structural stability to the superconductor. Resistivity temperature data are also provided for specific cases of interest.

Notes: Abstract A three sweep potentiokinetic technique was employed to study the electrochemical corrosion behaviour of Fe-50 at % Ni in .1N H2SO4 solution. The as received foil did not show any passivation but it was observed in case of Fe−Ni samples implanted with N2 + ions at an energy of 100keV. Also it was seen that the primary passivation potential Epp and the critical current density in the corrosion experiment decrease as the implanted nitrogen ion dose increases from 5*1015 to 1*1017 ions/cm2. The identification of products formed during corrosion experiment has been attempted with the help of conversion electron Mössbauer spectroscopy (CEMS), X-ray diffraction (XRD) and X-ray photoemission spectroscopic (XPS) techniques, and the possible mechanism of reactions is discussed with reference to their results.

Notes: Abstract The high temperature oxidation behavior of Fe50Ni50 alloy foils implanted with 100 KeV N2 + ions at a different dose values is studied by using the technique of conversion electron Mössbauer spectroscopy (CEMS). It has been shown that the implanted foils exhibit considerable adherence of scales and higher oxidation resistance as compared to the virgin foils. This excessive adherence of scales to the surface and higher resistance to oxidation of implanted samples is attributed to nickel enrichment in the surface layers. Various oxides of Fe, Ni and Fe−Ni are identified from the hyperfine interaction parameters of the corresponding CEMS spectra and also from x-ray diffraction measurements.