Papers by Keyword: Electron Microprobe Analysis

Abstract: A common and straightforward method for the standardisation in electron-probe microanalysis (EPMA) is the use of homogeneous reference materials prepared by various techniques such as by melting, sintering, high-temperature annealing and hot-pressing. The reference materials have to be analysed by independent methods accurately in order to define their “true” composition. For some compounds the preparation techniques are difficult because of their specific thermo-chemical properties (e.g. low diffusivities, high equilibrium nitrogen pressure, incongruent melting). In addition, many compounds show large homogeneity ranges with an a priori existing uncertainty in composition, contrary to what is generally preferred: to use compounds with a narrow homogeneity range (“line compounds”). For the latter, diffusional preparation techniques can be applied to yield diffusion layers instead of massive samples for standardisation. However, also single-phase samples with narrow homogeneity ranges can be prepared by diffusion, depending on the phase equilibria in the corresponding system. The presentation summarises efforts that have been made in order to prepare various reference materials for carbon and nitrogen standardisation of EPMA by various techniques. The boundary conditions such as phase stabilities, phase compositions and diffusion kinetics, which are important for their preparation to obtain well-defined reference samples are discussed. These samples were applied to various WDS/EPMA-based studies of phase diagrams and diffusion kinetics by means of Cameca SX 50 and SX 100 microprobes.

Abstract: SiO2 layers were deposited by reactive d.c ion sputtering (using 1keV Ar+ ion gun) from a high purity silicon target in an oxygen ambient. The base pressure in the deposition chamber was 4.7·10-9mbar, and the substrate temperature was held at 550 °C. The argon partial pressure during ion gun operation was 1·10-3mbar. Structural characterization of the films was performed by Rutherford backscattering spectrometry (RBS analysis), electron microprobe analysis, X-ray diffraction (XRD analysis) and Raman spectroscopy. Reactive sputtering proved to be efficient for the deposition of silica at an oxygen partial pressure of 2·10-4mbar and an electrical current on the target of 5.5mA.