Effect of oxygen concentration on the kinetics of oxygen loss and thermal donor formation in silicon at temperatures between 350°c and 500°c

We have measured thermal donor and interstitial oxygen concentrations during isothermal anneals in samples containing different initial concentrations of interstitial oxygen. The rate of donor formation is a strong function of oxygen concentration at all temperatures and depends on [Oi]3.5 at 450°C, similar to that found in previous studies. However the donor introduction rate tends asymptotically to a dependency on [Oi]2 at lower temperatures. At these same temperatures, the loss of interstitial oxygen from solution is described by a model of stable O2 dimer formation. These results show that O2 dimer formation is the rate limiting step in both oxygen loss and donor formation. If thermal donor defects contain more than two oxygen atoms then it is implied that oxygen dimers diffuse more rapidly than isolated oxygen atoms. © (1993) Trans Tech Publications, Switzerland

Gene Sequence and Mapping Data from Marek's Disease Virus and Herpesvirus of Turkeys: Implications for Herpesvirus Classification

Purified DNAs from Marek's disease virus (MDV) and the herpesvirus of turkeys (HVT) were randomly sheared and cloned into the M13 bacteriophage. Two-hundred and ten MDV and 130 HVT clones were sequenced to give representative samples of the genome sequences. The predicted amino acid sequences from these gammaherpes-viruses were compared to known sequences from other herpesviruses using computer analysis. Thirty-five MDV and 24 HVT genes were identified by comparison with varicella-zoster virus (VZV), an alphaherpesvirus. However, only 14 MDV and seven HVT genes, giving generally lower homology scores, were found by comparison with Epstein-Barr virus (EBV), a gammaherpesvirus, indicating that MDV and HVT sequences bear greater similarity to VZV than to EBV sequences. A number of sequences were mapped by hybridizing labelled M13 clones to Southern blots of restriction fragments of MDV or HVT DNA. The results were consistent with the MDV and HVT genomes being collinear with VZV

X-ray photoemission and absorption spectroscopy of supported nanoscale iron clusters

Fe particles with sizes in the range 1-5 nm, formed by a gas-aggregation method and deposited onto graphite and C-60 supports, were studied by x-ray photoemission spectroscopy, x-ray absorption spectroscopy, and magnetic linear dichroism. Clusters deposited onto a C-60 coated graphite substrate become embedded within the fullerene film, and have an increased resistance to oxidation compared to exposed clusters supported on a graphite surface. No evidence for hybridization between the electronic states of Fe and C-60 is seen. The magnetic dichroism signal of the exposed clusters increases sharply with the film thickness because of the increased cluster interactions