Metallic gallium was observed on the surfaces of GaN commercial samples following argon ion milling. SIMS measurements confirmed that the commercial GaN had approximately 0.02% bulk oxygen present. The SIMS signal was standardized using a specimen of known oxygen content, as determined by elastic recoil detection analysis using 200 MeV heavy ions of 197Au. Despite this 2–5% oxygen was observed by XPS in the bulk of the GaN after the argon ion milling. This oxygen is believed to be from the original surface oxide that re-cycles on the GaN surface during the ion milling. 相似文献
In this paper we present a new version of the ‘modified finite element method’ (MFEM) presented by Gresho, Chan, Lee and Upson.1 The main modification of the original algorithm is the introduction of a cost-effective and memory-saving iterative solver for the discretized Poisson equation for the pressure. The vectorization of the preconditioner has been especially considered. For low Prandtl number problems we also split the advection-diffusion operator of the energy equation into explicit and implicit parts. In that sense the present approach is related to the recent implicitization of the diffusive terms introduced by Gresho and Chan2 and by Gresho.3 The algorithm is applied to the study of buoyancy-driven flow oscillations occuring in a horizontal crucible of molten metal under the action of a horizontal temperature gradient. 相似文献
Summary Spark-source mass spectrometry was used for the determination of oxygen in gallium. Specially formed electrodes made of oxygen standard in gold matrix provided the possibility of baking the source together with the sample and obtaining a reliable comparison of line blackenings for the evaluation of results. The method was used for the detection of oxygen in gallium in the range of 8 to 200 ppmw.
Bestimmung von Sauerstoff in Gallium mit der Funken-Massenspektrometrie
Zusammenfassung Die Funken-Massenspektrometrie ist für die Bestimmung des Sauerstoffgehalts in Gallium eingesetzt worden. Mit speziell geformten Elektroden aus Gold mit bekannten Anteilen an Sauerstoff war es möglich, die Ionenquelle zusammen mit der Probe auszuheizen und über einen zuverlässigen Vergleich der Linienschwärzungen den Sauerstoffanteil der Probe zu erhalten. Diese Methode wurde eingesetzt, um Sauerstoffgehalte in Gallium zwischen 8 und 200 ppmw zu bestimmen.
An efficient and simple synthesis approach to form stable 68Ga‐labeled nanogels is reported and their fundamental properties investigated. Nanogels are obtained by self‐assembly of amphiphilic statistical prepolymers derivatised with chelating groups for radiometals. The resulting nanogels exhibit a well‐defined spherical shape with a diameter of 290 ± 50 nm. The radionuclide 68Ga is chelated in high radiochemical yields in an aqueous medium at room temperature. The phagocytosis assay demonstrates a highly increased internalization of nanogels by activated macrophages. Access to these 68Ga‐nanogels will allow the investigation of general behavior and clearance pathways of nanogels in vivo by nuclear molecular imaging.
A simple quasi-thermodynamic model of surface chemistry in GaN hydride vapor phase epitaxy (HVPE) is presented. The model is coupled with the detailed 3D simulations of species transport in a horizontal-tube reactor and validated by the comparison with the data on the GaN growth rate obtained by laser reflectometry. Parametric study of the growth rate as a function of temperature and species flow rates has been performed over a wide range of growth conditions. The important role of species transport in an HVPE reactor is demonstrated. In particular, a strong effect of the natural concentration convection resulting in the formation of recirculation zones and in a non-uniform vapor composition is revealed by modeling. The impact of these effects on the GaN growth rate and V/III ratio on the growth surface is discussed in detail. 相似文献
