An investigation of the interaction of N2O with the Si(111)-7 × 7 surface using AES and optical reflectometry; A comparison with O2

At 300 K, N2O decomposes into N2, leaving behind atomic oxygen at the Si(111)¿7 × 7 surface. Decomposition at two different sites is proposed, having the overall initial reaction probability: s(0) = (6.7 ± 0.7) × 106. SiOx(x not, vert, similar 1) bonds are predominantly formed, saturation occurring at monolayer coverage. This oxygen monolayer appears to completely prevent further oxygen uptake by additional N2O or O2 exposures, in contrast with the adsorption behaviour of O2 on Si(111)-7 × 7, which exhibits slow sorption beyond one monolayer

Adsorption of atomic oxygen (N2O) on a clean Si(100) surface and its influence on the surface state density; A comparison with O2

This paper describes a study concerning the interaction of molecular oxygen (O2) and nitrous oxide (N2O) with the clean Si(100) 2 × 1 surface in ultrahigh vacuum at 300 K. Differential reflectometry (DR) in the photon energy range of 1.5¿4.5 eV, Auger electron spectroscopy (AES) and low energy electron diffraction (LEED) have been used to monitor these solid-gas reactions. With this combination of techniques it is possible to make an analysis of the (geometric and electronic) structure and chemical composition of the surface layer. The aim of the present study was to give a description of the geometric nature of the oxygen covered Si(100) surface. For that purpose we have used both molecular (O2) and atomic oxygen (as released by decomposition of N2O) to oxidize the clean Si(100)2 × 1 surface

The adsorption and decomposition of carbon monoxide on Ni(100) and the oxidation of the surface carbide by oxygen

The interaction of carbon monoxide with Ni(100) has been studied by ellipsometry and Auger electron spectroscopy. Bombardment by electrons of a relatively high energy (2500 eV) leads to the disproportionation of the adsorbed CO (2 COad → Cad + CO2g ). The rate of oxidation of this surface carbide is , where hc is the carbon 272 eV Auger peak height, n=0.5 and the apparent activation energy Eact =13.3 kcal/mole. This relation is valid at 200–400°C and at oxygen pressures of 5 × 10−9−8 × 10−7 Torr

Structural and chemical evolution of single-wall carbon nanotubes under atomic and molecular deuterium interaction

The interaction of atomic (D) and molecular (D2) deuterium, as present in a (D + D2) gas mixture, with single-wall carbon nanotubes (SWNTs) has been studied by means of a combination of scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The SWNT samples were exposed to the gas mixture, produced by thermal dissociation of D2 on a hot W filament, its temperature, TW, being kept at 1020 and 1550 K for a deuterium pressure of 0.6 and 60 Pa, respectively. Prolonged interaction of the low-pressure (D + D2) gas mixture produced at TW = 1020 K leads to a conglomeration of the SWNT bundles into larger diameter ropes of square and triangular cross-section, covered by nano-aggregates of graphite material. Both the coalescence of single SWNTs and a massive reconstruction of bundles of SWNTs into a “coral reef”-like structure were found to occur after prolonged exposure of SWNTs to the high-pressure (D + D2) gas mixture produced at TW = 1550 K. This structure is formed by the encapsulated Fe nanoparticles and deuterocarbon-like species appearing as a result of the deuterium interaction with the SWNT bundles accompanied by partial erosion of the SWNT material. The XPS valence-band spectra disclose electronic features characteristic for a hydrogen-plasma modified multi-wall carbon nanotube (MWNT)-like structure as a result of an intensive (D + D2) induced transformation of the SWNTs into the “coral reef”-like structure

Microstructural and chemical transformation of thin Ti/Pd and TiDy/Pd bi-later films induced by vacuum annealing

Using a combination of scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction and X-ray photoelectron spectroscopy (XPS), we made a comparative study of the high-temperature annealing impact on thin titanium deuteride (TiD y ) films covered by an ultrathin Pd layer, and on Ti/Pd bilayer films. The bilayer films were prepared under ultrahigh vacuum conditions and were in situ annealed using the same annealing procedure. It was found that the surface and the bulk morphology of both films undergo different annealing-induced transformations, leading to an extensive intermixing between the Ti and Pd layers and the formation of a new PdTi2 bimetallic phase. Energy-filtered TEM imaging and energy-dispersive X-ray spectrometry analysis, as well as XPS depth profiling all provided evidence of a different distribution of Pd and Ti in the annealed TiD y /Pd film compared with the annealed Ti/Pd film. Our results show that thermal decomposition of TiD y , as a consequence of annealing the TiD y /Pd film, modifies the intermixing process, thereby promoting Ti diffusion into the Pd-rich top layer of the TiD y film and thus providing a more likely path for the formation of the PdTi2 phase than in an annealed Ti/Pd fil

Ab initio optical properties of Si(100)

We compute the linear optical properties of different reconstructions of the clean and hydrogenated Si(100) surface within DFT-LDA, using norm-conserving pseudopotentials. The equilibrium atomic geometries of the surfaces, determined from self-consistent total energy calculations within the Car-Parrinello scheme, strongly influence Reflectance Anisotropy Spectra (RAS), showing differences between the p(2x2) and c(4x2)reconstructions. The Differential Reflectivity spectrum for the c(4x2) reconstruction shows a positive peak at energies < 1 eV, in agreement with experimental results.Comment: fig. 2 correcte

Size Doesn't Matter: Towards a More Inclusive Philosophy of Biology

notes: As the primary author, O’Malley drafted the paper, and gathered and analysed data (scientific papers and talks). Conceptual analysis was conducted by both authors.publication-status: Publishedtypes: ArticlePhilosophers of biology, along with everyone else, generally perceive life to fall into two broad categories, the microbes and macrobes, and then pay most of their attention to the latter. ‘Macrobe’ is the word we propose for larger life forms, and we use it as part of an argument for microbial equality. We suggest that taking more notice of microbes – the dominant life form on the planet, both now and throughout evolutionary history – will transform some of the philosophy of biology’s standard ideas on ontology, evolution, taxonomy and biodiversity. We set out a number of recent developments in microbiology – including biofilm formation, chemotaxis, quorum sensing and gene transfer – that highlight microbial capacities for cooperation and communication and break down conventional thinking that microbes are solely or primarily single-celled organisms. These insights also bring new perspectives to the levels of selection debate, as well as to discussions of the evolution and nature of multicellularity, and to neo-Darwinian understandings of evolutionary mechanisms. We show how these revisions lead to further complications for microbial classification and the philosophies of systematics and biodiversity. Incorporating microbial insights into the philosophy of biology will challenge many of its assumptions, but also give greater scope and depth to its investigations