Arne Olsen

Argyria—tissue deposition of silver as selenide

Generalized argyria was precipitated in a patient by treating gingival erosions with a solution of silver nitrate for several months. High silver concentrations were measured in skin biopsies. treatment with penicillamine did not increase the urinary silver excretion, indicating that silver is deposited in tissues in a chemically stable and apparently inert form. Electron microscopy showed that in the kidney, silver was deposited mainly in the basal membranes as electron-dense particles. These particles were studied by using X-ray emission spectrometry and electron diffraction. the particles consisted of Ag2Se in the low temperature orthorhombic alfaform. The lattice parameters are: a = 0.433 nm, b = 0.693 nm and c = 0.784 nm. This selenide complex seems to be remarkably non-toxic, since the renal function of the patient was unaffected and only negligible reactive changes were observed in kidney biopsies.

The passive behaviour of Mg in alkaline fluoride solutions. Electrochemical and electron microscopical investigations

Abstract The passive behaviour of pure Mg at 25°C was studied by electrochemical methods in solutions of pH 7–14 containing 0–4 M KF. The dependences of the quasi-steady corrosion current density on pH and [KF] were assessed. Solutions of NaF and NH 4 F were also tested. The corrosion films were examined by SEM, TEM and AES. Porous, gel-like Mg(OH) 2 films were formed in solutions with small, or no, additions of KF. At high [KF], very protective films were formed (corrosion current densities 10 −9 −10 −8 A cm −2 ). The composition of these films was not identified. MgF 2 and KMgF 3 were identified by electron diffraction in some other corrosion films.

High-resolution electron microscopy and X-ray diffraction studies of MCM-48

Abstract A cubic member of the M41S family with a three-dimensional pore system, denoted as MCM-48, was synthesised. By combining X-ray powder diffraction (XRD) with high-resolution electron microscopy (HREM), a cubic symmetry with an Ia 3 d space group was determined for the as-synthesised and the calcined MCM-48 material. Upon calcination the unit cell decreased from around 10.09 nm to about 8.1 nm. The overall pore structure was found to be quite unaffected by local variations in the structure and the decrease in the unit cell size upon calcination.

Phase relations and crystal structures in the Ag–Ga system

Abstract The Ag–Ga phase diagram and the ζ-Ag2Ga↔ζ′-Ag2Ga transformation have been investigated by use of optical, scanning and transmission electron microscopy combined with X-ray powder diffraction and thermal differential analysis. On the basis of the present study a new equilibrium phase diagram for the Ag–Ga system is proposed. Only two intermetallic phases are found in the Ag–Ga system: ζ′ and ζ. The compositional change of Ga in ζ′ is described by replacing Ga atoms in 1b position in space group P 6 2m with Ag atoms. In alloys having 25–40 wt.% Ga, the high temperature ζ-Ag2Ga is found to decompose into a Ga-rich liquid and solid ζ′-Ag2Ga at 302°C. In Ga-poor alloys (15 wt.%), the high temperature ζ-Ag2Ga is found to decompose into α-Ag and liquid at 611°C and into α-Ag and ζ′-Ag2Ga at 395°C.

HREM study of dispersoids in cryomilled oxide dispersion strengthened materials

Abstract Thin platelets (dispersoids) only a few atomic layers thick formed in cryomilled oxide dispersion strengthened aluminium, have been investigated by high-resolution electron microscopy (HREM). In order to interpret the experimental images, computer simulations of HREM images based on different structure models have been carried out. The image simulations have been used to determine the composition and the structure of the dispersoids. Two types of dispersoids have been found: one type consists of a single layer of nitrogen with the nitrogen atoms in tetrahedral positions in aluminium, the other type consists of one single layer of oxygen with the oxygen atoms in octahedral positions in aluminium.

An experimental study of charge distribution in crystalline and amorphous Si nanoclusters in thin silica films

Crystalline and amorphous nanoparticles of silicon in thin silica layers were examined by transmission electron microscopy, electron energy loss spectroscopy, and x-ray photoelectron spectroscopy (XPS). We used XPS data in the form of the Auger parameter to separate initial and final state contributions to the Si2p energy shift. The electrostatic charging and electron screening issues as well as initial state effects were also addressed. We show that the chemical shift in the nanocrystals is determined by initial state rather than final state effects, and that the electron screening of silicon core holes in nanocrystals dispersed in SiO2 is inferior to that in pure bulk Si.

Introduction of Si∕SiO2 interface states by annealing Ge-implanted films

Nanocrystals embedded in SiO2 films are the subject of a number of recent works, mainly because of their potential usefulness in the fabrication of optoelectronic devices and nanocrystal memory structures. One interesting method for the fabrication of such nanocrystals is the ion implantation of segregating species into SiO2 films followed by heat treatment in order to induce nanocrystal formation. This method is both relatively simple and also compatible with the current MOS (metal-oxide-semiconductor) device technology. An unintentional effect can occur during the fabrication of nanocrystals using this method, namely a significant diffusion of the implanted species during annealing, away from the regions with the highest concentration. The Si∕SiO2 interface can be exposed to this diffusion flux. This can result in an altered interface and have a significant influence on electronic devices. Here, we report on ion implantation of Ge into SiO2 on Si followed by annealing under conditions, resulting in Ge a...

Nanocrystal and nanocluster formation and oxidation in annealed Ge-implanted SiO2 films

Abstract There has been much interest in semiconductor nanocrystals embedded in oxides and their interesting optical and electrical properties, which can potentially be utilised in future devices. We have studied the effects of different processing parameters on the formation of Ge nanocrystals in SiO2 prepared by ion implantation followed by heat treatment. We implanted Ge doses of between 2×1015 and 1×1017 cm−2 at implantation energy of 30 or 100 keV and used a range of annealing temperatures and times. The samples were investigated using transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy (EDS), secondary ion mass spectroscopy (SIMS) and Raman spectroscopy. Ge nanocrystals were observed for doses of 3×1016 and 1×1017 cm−2 at 100 keV after annealing at 800 °C. Annealing of similar samples at 1000 °C yielded no nanocrystals. We believe that diffusion of oxidising species from the atmosphere is important and that this process is faster at 1000 than at 800 °C, creating Ge-rich amorphous oxides rather than Ge nanocrystals at the higher temperature. This oxidation process also explains the absence of Ge nanocrystals in SiO2 films implanted with Ge at 30 keV after annealing. Electron beam-induced precipitation was observed in samples with amorphous Ge-rich layers under intense electron irradiation in the TEM. Accumulation of Ge at the Si/SiO2 interface was observed in samples implanted at 100 keV and annealed at 1000 °C or higher temperatures.

Platelet defects in natural diamond. II: Determination of structure

Abstract High-resolution lattice images of two of the platelets used in the displacement measurements in the previous paper (Part I) have been used in image matching experiments in an effort to determine the structure of the platelets. This process was complicated by the fact that the structure of these platelets has been altered to some degree by radiation damage, as indicated by their non-zero component of displacement parallel to the plane of the platelets. However, since the value of the normal displacement of both platelets was close to the mean value determined in Part I,0.39 a o, it was assumed that the damage was not severe and that the observed component of displacement parallel to the platelet could be simulated by the appropriate rigid-body shear of the atomic coordinates pertaining to the ideal, undamaged models. In addition to three models for the structure of platelets previously proposed in the literature, several new models were developed and the images of all these were computed and compa...

Determination of the crystal structure of the π-AlFeMgSi phase using symmetry- and site-sensitive electron microscope techniques

The crystal structure of the complex pi-AlFeMgSi phase, which was previously thought to have the composition Al(8)FeMg(3)Si(6), has been investigated. Microprobe analysis revealed that the phase has a different composition, Al(9)FeMg(3)Si(5). The space group was determined and confirmed to be P62m with the use of parallel-beam electron diffraction (SAD) and convergent-beam electron diffraction (CBED). Owing to symmetry considerations the elements within the unit cell had to be rearranged. The rearrangement was confirmed using electron channelling. The z parameters of the elements were refined by examining the intensities from high-angle convergent-beam electron diffraction. Finally, the x parameters were adjusted slightly to arrive at acceptable interatomic distances.