Julian Ikonomov

XPS and SEM characterization of zirconia thin films prepared by electrochemical deposition

Electrochemical deposition of zirconia on stainless steel has been investigated in order to provide supports of catalysts for No x reduction. The zirconia films have been obtained in electrolytes based on anhydrous ethyl alcohol. The structure and chemical composition of the films have been characterized by SEM and XPS depth profiling. With rising cathodic voltage, the structure and morphology exhibit essential changes. The most porous structure corresponds to films formed at 21 V, whereas the highest density is achieved at 25 V. The XPS depth profiling data show that the composition in the bulk of the films is close to stoichiometric. The cross-section of an annealed film gives evidence for good adhesion to the substrate. The film thickness is 3-10 μm. After annealing in air at 550°C for 1 h, no cracks and inhomogeneities are observed.

Steady-state surface stress induced in noble gas sputtering

We have measured the surface stress on single crystal Cu(100) surfaces as induced by bombardment of the surface with the noble gas ions Ar, Ne and He at room temperature. Regardless of the ion type and energy, the induced stress is compressive and saturates as a function of sputter time at a value between 2 and 15 N/m. Saturation time and magnitude of the induced stress depend on the ion species and their energy. The time dependence can be accounted for by assuming a steady state thickness of a defective surface layer, which arises from a balance between sputtering and ion implantation.

XPS and SEM characterization of electrodeposited transition metals on zirconia

Abstract The structure and chemical composition of electrochemically deposited cobalt, copper and cobalt+copper on zirconia have been investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and scanning Auger microscopy (SAM) methods. It has been established that as-deposited metal crystallites are mainly formed on the macroconcavities of an electrochemically roughened SS 1.4301 substrate. In the facet zones, the crystallites are much smaller and have a good dispersion. In this case, the cobalt on the surface is present as Co2+, while copper is found as Cu+. The deposited metal crystallites show no substantial changes in structure after thermal oxidation, which leads to the formation of considerably thicker oxide layers on the metal crystallites where cobalt and copper are in the Co3+ nd Cu2+ states. The cobalt and copper oxides obtained on ZrO2 are characterized by good adhesion and cause no change in the specific surface area of porous zirconia films. Modification of the structure, composition and dispersion of the oxide systems under consideration is promising, with a view to their application as thin porous inorganic catalytic films.

Surface modification of porous zirconia layers by electrochemical deposition of small amounts of Cu or Co and Co + Cu

The possibility of modifying the surface structure and chemical composition of zirconia layers on stainless steel by electrochemical deposition of definite amounts of Co, Cu or Co + Cu has been examined. Scanning Auger microscopy studies have revealed the formation of a dispersed layer of metal crystallites on zirconia. Annealing in air at 450 °C causes oxidation of the metal phases and, as a result, the formation of CuO and Co2O3. Copyright

Determining molecule diffusion coefficients on surfaces from a locally fixed probe: Analysis of signal fluctuations

Methods of determining surface diffusion coefficients of molecules from signal fluctuations of a locally fixed probe are revisited and refined. Particular emphasis is put on the influence of the molecules extent. In addition to the formerly introduced autocorrelation method and residence time method, we develop a further method based on the distribution of intervals between successive peaks in the signal. The theoretical findings are applied to STM measurements of copper phthalocyanine (CuPc) molecules on the Ag(100) surface. We discuss advantages and disadvantages of each method and suggest a combination to obtain accurate results for diffusion coefficients.

Computer reconstruction of two-dimensional random rough surfaces from scattered light measurement

The profile of a two-dimensional random rough surface is visualized by computer processing. For this purpose the studied surface is scanned by a thin light line (with a width of 30 ?m), for which the surface profile appears one-dimensional. The reference (the field of the laser beam), the scattered and the mixed fields (the field obtained from the mixing of the reference and the scattered fields) are registered for every light line [1]. The surface profile illuminated by every light line is expanded in a Fourier series as a sum of sinusoidal gratings. The surface is reconstructed by subsequent computer processing of the optical fields since the obtained one-dimensional profiles are arranged in the same way as during the scanning. Solutions for the amplitudes of all the harmonics in a Fourier series for every light line are found utilizing the Kirchhoff approximation. The surface is scanned with 100 lines over a 20 ?m distance. The studied surface is three-dimensionally visualized. The statistical parameters such as the mean roughness Ra , root mean square , and correlation length are calculated for every line along with the mean values of these parameters for the whole surface. The obtained Ra and values are in good agreement with those measured by a contact pin method.