[1] Olivine is an important host of hydrogen in the Earth's upper mantle, and the OH abundance in this mineral determines many important physical properties of the planet's interior. To date, natural and experimentally hydrated olivines have been analyzed by uncalibrated spectroscopic methods with large (±100%) uncertainties in accuracy. We determined the hydrogen contents of three natural olivines by 15 N nuclear reaction analysis and used the results to calibrate the common infrared (IR) spectroscopic method for quantitative hydrogen analysis of olivine. OH content (expressed as parts per million H 2 O by weight) is 0.188 times the total integrated absorbance of the fundamental OH stretching bands in the 3750-3100 cm À1 region. The results indicate that an upward revision of some previous determinations by factors of between 2 and 4 is necessary. The most hydrous naturally occurring mantle-derived olivine analyzed to date contains 240 ppm wt. H 2 O. Retrospective application of this calibration to experimentally hydrated olivines may be limited by spectral differences in some cases and by the previous use of nonpolarized IR spectra.

We investigated in detail the strain relaxation behaviour of metastable tensile-strained Si 1−y C y epilayers on Si(001) by comparing the layers before and after an annealing step using a variety of different diagnostic methods. The dominant strain-relieving mechanism is the formation of carbon-containing interstitial complexes and/or silicon carbide nanoparticles, similar to the behaviour of carbon in silicon under thermodynamical equilibrium conditions (concentrations below the solid bulk solubility limit). We did not observe any carbon out-diffusion. To grow material suitable for device applications, all carbon atoms should be incorporated substitutionally. There is only a very narrow temperature window for perfect epitaxial growth of such layers, limited on one side by the possible formation of interstitial carbon complexes and on the other side by the deterioration of epitaxial growth at low temperatures. The carbon concentration should not exceed a few per cent to avoid strain-driven precipitation.

No abstract

No abstract

No abstract