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End date: 2019 × Start date: 2010 × Subject: silicon × WGL Institute: IKZ ×

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Now showing 1 - 4 of 4
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    Electronic materials with a wide band gap: Recent developments
    (Chester : International Union of Crystallography, 2014) Klimm, D.
    The development of semiconductor electronics is reviewed briefly, beginning with the development of germanium devices (band gap E g = 0.66 eV) after World War II. A tendency towards alternative materials with wider band gaps quickly became apparent, starting with silicon (E g = 1.12 eV). This improved the signal-to-noise ratio for classical electronic applications. Both semiconductors have a tetrahedral coordination, and by isoelectronic alternative replacement of Ge or Si with carbon or various anions and cations, other semiconductors with wider E g were obtained. These are transparent to visible light and belong to the group of wide band gap semiconductors. Nowadays, some nitrides, especially GaN and AlN, are the most important materials for optical emission in the ultraviolet and blue regions. Oxide crystals, such as ZnO and β-Ga2O3, offer similarly good electronic properties but still suffer from significant difficulties in obtaining stable and technologically adequate p-type conductivity.
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    Violation of a Leggett-Garg inequality with ideal non-invasive measurements
    (London : Nature Publishing Group, 2012) Knee, G.C.; Simmons, S.; Gauger, E.M.; Morton, J.J.L.; Riemann, H.; Abrosimov, N.V.; Becker, P.; Pohl, H.-J.; Itoh, K.M.; Thewalt, M.L.W.; Briggs, G.A.D.; Benjamin, S.C.
    The quantum superposition principle states that an entity can exist in two different states simultaneously, counter to our 'classical' intuition. Is it possible to understand a given system's behaviour without such a concept? A test designed by Leggett and Garg can rule out this possibility. The test, originally intended for macroscopic objects, has been implemented in various systems. However to date no experiment has employed the 'ideal negative result' measurements that are required for the most robust test. Here we introduce a general protocol for these special measurements using an ancillary system, which acts as a local measuring device but which need not be perfectly prepared. We report an experimental realization using spin-bearing phosphorus impurities in silicon. The results demonstrate the necessity of a non-classical picture for this class of microscopic system. Our procedure can be applied to systems of any size, whether individually controlled or in a spatial ensemble.
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    Si:P as a laboratory analogue for hydrogen on high magnetic field white dwarf stars
    (London : Nature Publishing Group, 2013) Murdin, B.N.; Li, J.; Pang, M.L.Y.; Bowyer, E.T.; Litvinenko, K.L.; Clowes, S.K.; Engelkamp, H.; Pidgeon, C.R.; Galbraith, I.; Abrosimov, N.V.; Riemann, H.; Pavlov, S.G.; Hübers, H.-W.; Murdin, P.G.
    Laboratory spectroscopy of atomic hydrogen in a magnetic flux density of 10 5 T (1 gigagauss), the maximum observed on high-field magnetic white dwarfs, is impossible because practically available fields are about a thousand times less. In this regime, the cyclotron and binding energies become equal. Here we demonstrate Lyman series spectra for phosphorus impurities in silicon up to the equivalent field, which is scaled to 32.8 T by the effective mass and dielectric constant. The spectra reproduce the high-field theory for free hydrogen, with quadratic Zeeman splitting and strong mixing of spherical harmonics. They show the way for experiments on He and H 2 analogues, and for investigation of He 2, a bound molecule predicted under extreme field conditions.
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    A new generation of 99.999% enriched 28Si single crystals for the determination of Avogadro's constant
    (Sèvres : Bureau, 2017) Abrosimov, N.V.; Aref’ev, D.G.; Becker, P.; Bettin, H.; Bulanov, A.D.; Churbanov, M.F.; Filimonov, S.V.; Gavva, V.A.; Godisov, O.N.; Gusev, A.V.; Kotereva, T.V.; Nietzold, D.; Peters, M.; Potapov, A.M.; Pohl, H.-J.; Pramann, A.; Riemann, H.; Scheel, P.-T.; Stosch, R.; Wundrack, S.; Zakel, S.
    A metrological challenge is currently underway to replace the present definition of the kilogram. One prerequisite for this is that the Avogadro constant, NA, which defines the number of atoms in a mole, needs to be determined with a relative uncertainty of better than 2  ×  10−8. The method applied in this case is based on the x-ray crystal density experiment using silicon crystals. The first attempt, in which silicon of natural isotopic composition was used, failed. The solution chosen subsequently was the usage of silicon highly enriched in 28Si from Russia. First, this paper reviews previous efforts from the very first beginnings to an international collaboration with the goal of producing a 28Si single crystal with a mass of 5 kg, an enrichment greater than 0.9999 and of sufficient chemical purity. Then the paper describes the activities of a follow-up project, conducted by PTB, to produce a new generation of highly enriched silicon in order to demonstrate the quasi-industrial and reliable production of more than 12 kg of the 28Si material with enrichments of five nines. The intention of this project is also to show the availability of 28Si single crystals as a guarantee for the future realisation of the redefined kilogram.