Characterization of SiGe/Si Heterostructures Formed by Ge+ and C+ Implantation

Formation of SiGe/Si heterostructures by germanium ion implantation was investigated. A germanium‐implanted layer was grown epitaxially in the solid phase by thermal annealing. Two kinds of crystalline defects were observed. One is a misfit dislocation, and the other is a residual dislocation caused by ion bombardment. The p‐n junction formed in the SiGe layer has a leakage current three orders of magnitude larger than that of a pure Si p‐n junction fabricated with an identical process except for the Ge+ implantation. Carbon doping in the SiGe layer improves its crystalline quality and the junction characteristics

Improved Crystalline Quality of Si\u3csub\u3e1-x\u3c/sub\u3eGe\u3csub\u3ex\u3c/sub\u3e Formed by Low-temperature Germanium Ion Implantation

Improvement of crystalline quality in Si1-xGex formed by germanium ion implantation has been found. End‐of‐range defects were drastically reduced in number by lowering the substrate temperature during implantation with doses on the order of 1016 cm−2. This improvement was confirmed by electrical characterization of p‐n junctions formed in the SiGe layer as well as by transmission electron microscopy

Re/Os constraint on the time-variability of the fine-structure constant

We argue that the accuracy by which the isochron parameters of the decay $^{187}{\rm Re}\to ^{187}{\rm Os}$ are determined by dating iron meteorites may not directly constrain the possible time-dependence of the decay rate and hence of the fine-structure constant $\alpha$. From this point of view, some of the attempts to analyze the Oklo constraint and the results of the QSO absorption lines are re-examined.Comment: 7 pages, 3 figures; v2, revised top sentence on p.

Nucleosynthesis in novae: experimental progress in the determination of nuclear reaction rates

The sources of nuclear uncertainties in nova nucleosynthesis have been identified using hydrodynamical nova models. Experimental efforts have followed and significantly reduced those uncertainties. This is important for the evaluation of nova contribution to galactic chemical evolution, gamma--ray astronomy and possibly presolar grain studies. In particular, estimations of expected gamma-ray fluxes are essential for the planning of observations with existing or future satellites.Comment: Invited contribution to the "Origin of Matter and Evolution of Galaxies" conference (OMEG07) with additional and color figure

Big-Bang Nucleosynthesis with Unstable Gravitino and Upper Bound on the Reheating Temperature

We study the effects of the unstable gravitino on the big-bang nucleosynthesis. If the gravitino mass is smaller than \sim 10 TeV, primordial gravitinos produced after the inflation are likely to decay after the big-bang nucleosynthesis starts, and the light element abundances may be significantly affected by the hadro- and photo-dissociation processes as well as by the p n conversion process. We calculate the light element abundances and derived upper bound on the reheating temperature after the inflation. In our analysis, we calculate the decay parameters of the gravitino (i.e., lifetime and branching ratios) in detail. In addition, we performed a systematic study of the hadron spectrum produced by the gravitino decay, taking account of all the hadrons produced by the decay products of the gravitino (including the daughter superparticles). We discuss the model-dependence of the upper bound on the reheating temperature.Comment: 32 pages, 11 figure

Explosions inside Ejecta and Most Luminous Supernovae

The extremely luminous supernova SN2006gy is explained in the same way as other SNIIn events: light is produced by a radiative shock propagating in a dense circumstellar envelope formed by a previous weak explosion. The problems in the theory and observations of multiple-explosion SNe IIn are briefly reviewed.Comment: 9 pages, 6 figures, LateX aipproc.cls. A bit more details and color added to Fig.3. The 10th International Symposium on Origin of Matter and Evolution of Galaxies (OMEG07), Sapporo, Japan, December 200

High-spectral resolution observations of the 3.29 micron emission feature: Comparison to QCC and PAHs

Two of the most promising explanations for the origin of the interstellar emission features observed at 3.29, 3.4, 6.2, 7.7, 8.6, and 11.3 microns are: quenched carbonaceous composite (QCC) and polycyclic aromatic hydrocarbons (PAHs). High resolution spectra are given of the 3.29 micron emission feature which were taken with the Cooled Grating Array Spectrometer at the NASA Infrared Telescope Facility and previously published. These spectra show that the peak wavelength of the 3.29 micron feature is located at 3.295 + or - 0.005 micron and that it is coincident with the peak absorbance of QCC. The peak wavelength of the 3.29 micron feature appears to be the same in all of the sources observed thus far. However, the width of the feature in HD 44179 and Elias 1 is only 0.023 micron, which is smaller than the 0.043 micron width in NGC 7027, IRAS 21282+5050, the Orion nebula, and BD+30 deg 3639. Spectra of NGC 7027, QCC, and PAHs is shown. QCC matches the 3.29 micron interstellar emission feature very closely in the wavelength of the peak, and it produces a single feature. On the other hand, PAHs rarely match the peak of the interstellar emission feature, and characteristically produce multiple features

Recent Efforts in Data Compilations for Nuclear Astrophysics

Some recent efforts in compiling data for astrophysical purposes are introduced, which were discussed during a JINA-CARINA Collaboration meeting on "Nuclear Physics Data Compilation for Nucleosynthesis Modeling" held at the ECT* in Trento/ Italy from May 29th- June 3rd, 2007. The main goal of this collaboration is to develop an updated and unified nuclear reaction database for modeling a wide variety of stellar nucleosynthesis scenarios. Presently a large number of different reaction libraries (REACLIB) are used by the astrophysics community. The "JINA Reaclib Database" on http://www.nscl.msu.edu/\~nero/db/ aims to merge and fit the latest experimental stellar cross sections and reaction rate data of various compilations, e.g. NACRE and its extension for Big Bang nucleosynthesis, Caughlan and Fowler, Iliadis et al., and KADoNiS. The KADoNiS (Karlsruhe Astrophysical Database of Nucleosynthesis in Stars, http://nuclear-astrophysics.fzk.de/kadonis) project is an online database for neutron capture cross sections relevant to the s process. The present version v0.2 is already included in a REACLIB file from Basel university (http://download.nucastro.org/astro/reaclib). The present status of experimental stellar $(n,\gamma)$ cross sections in KADoNiS is shown. A "high priority list" for measurements and evaluations for light charged-particle reactions set up by the JINA-CARINA collaboration is presented. The central web access point to submit and evaluate new data is provided by the Oak Ridge group via the http://www.nucastrodata.org homepage. "Workflow tools" aim to make the evaluation process transparent and allow users to follow the progress.Comment: Proceedings 10th Int. Symp. on Origin of Matter and Evolution of Galaxies OMEG07, Sapporo/ Japan, December 4-7 200