Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

Ultrathin metal films and particles on oxide surfaces: structural, electronic and chemisorptive properties

Surface studies of supported model catalysts

http://w0.rz-berlin.mpg.de/hjfdb/pdf/260e.pdf

Metal deposits on well-ordered oxide films

Nanostructured oxides in chemistry: characterization and properties.

We have prepared ordered thin films of NiO and CoO in (100) orientation by evaporating Ni (Co) in an O2 atmosphere onto Ag(100). The films have been analysed by scanning tunnelling microscopy and low-energy electron diffraction. In the initial stage (coverage up to a few monolayers), growth and structure of the grown films drastically depend on the preparation conditions (in particular, on the temperature of the substrate during deposition and post-annealing). In this case we also observe strong interactions with the substrate. Ag atoms are partially removed from the substrate terraces and form islands or migrate to step edges. No indications for incorporation in the oxide thin films are seen. The oxidic features grow on top of the substrate or in the vacancy islands within the first layer of the substrate left behind by the removed Ag atoms. At low substrate temperatures (near room temperature) an essential part of the oxidic features corresponds to a precursor state rather than to the fully developed (100) oxide film which only develops after post-annealing to higher temperatures (typically around 500 K). I/U characteristics and the sample bias dependency of the contrast of the islands grown have been utilised for identification of whether an oxide reaction had taken place or not. The surfaces of the oxide precursor show a typical defect structure similar to those found on cleaved NiO(100) (M. R. Castell etal., Phys. Rev. B:Condens. Matter, 1997, 55, 7859). This feature shows ‘random walk’ at room temperature.

Scanning tunnelling microscopy on the growth and structure of NiO(100) and CoO(100) thin films

Small metal particles have strongly size-dependent properties, which - in the case of supported particles - are also influenced by the particle substrate interaction. We have investigated such effects for Pd deposited on a thin alumina film grown on NiAl(i10) by probing the adsorption behaviour of CO. Structure and size of the metal islands were varied by employing different substrate temperatures during evaporation. We found that at 90 K small, disordered aggregates are formed, whereas deposition at 300 K results in larger crystallites with (111) facets. The CO thermal desorption spectra show a size-dependent behaviour which can be attributed to a higher degree of CO coordination with decreasing particle size. The results are compared with the corresponding behaviour of Pt. In contrast to Pd, Pt leads to a strong interaction with the substrate at 300 K. This gives rise to a desorption feature of CO in a temperature range which is typical for transition metal oxides.

The growth and properties of Pd and Pt on Al2O3/NiAl(110)

We have prepared thin ordered NiO(100) films by evaporation of Ni in an O2 atmosphere onto Ag(100). The films have been analyzed by using scanning tunneling microscopy and low‐energy electron diffraction. For room temperature deposition a c(1×2) Ni/O Ag structure in two orthogonal domains is obtained in the submonolayer coverage range. Annealing such a film produces regular islands with NiO(100) double layers. For higher coverage (five monolayers) a layer‐by‐layer‐like growth mode is obtained.

Growth of NiO(100) layers on Ag(100): Characterization by scanning tunneling microscopy

By controlled oxidation of a clean NiAl(110) surface an epitaxial thin layer of Al2O3 may be grown. The oxide layer shows a sharp low‐energy electron diffraction pattern of two domains of nearly rectangular unit cells. A stable tunneling current was obtained for a wide range of sample bias voltages U (from a few mV up to nearly 10 V). For U in the mV range the images essentially contain contributions of the interface layer, which can be measured with atomic resolution. For large U (e.g., 4 V) the electronic states of the oxide film contributed additionally to the substrate electrons, which allows an accurate analysis of the growth mode of the oxide film.

Henning Neddermeyer

Papers

Scanning tunnelling microscopy on the growth and structure of NiO(100) and CoO(100) thin films

The growth and properties of Pd and Pt on Al2O3/NiAl(110)

Growth of NiO(100) layers on Ag(100): Characterization by scanning tunneling microscopy

Tunneling through an epitaxial oxide film: Al2O3 on NiAl(110)

Evolution of surface morphology of Si(100)-(2×1) during oxygen adsorption at elevated temperatures