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  • American Institute of Physics (AIP)  (19)
  • International Union of Crystallography (IUCr)  (15)
  • Nature Publishing Group  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    Modeling of zinc-indiffusion-induced disordering of GaAs/AlAs superlattices (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 150-157 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A model for the effect of Zn indiffusion on enhancing the GaAs/AlAs superlattice (SL) disordering process, which combines recently proposed models for Ga self-diffusion and Zn diffusion in GaAs, is presented. Four coupled partial differential equations describing the process were solved numerically. Satisfactory agreement between the simulated results and experimental data available in the literature is obtained. At a given temperature, the used values for the diffusion coefficient and the thermal equilibrium concentration of the responsible point defect species, the doubly positively charged Ga self-interstitials IGa2+, are a consistent splitting of the known Ga self-diffusion coefficient dominated by IGa2+. Quantitatively, the SL disordering enhancement is mainly due to the Fermi-level effect while an IGa2+ supersaturation also makes a small contribution. Because of p-doping by Zn acceptor atoms, the IGa2+ concentration is increased tremendously via the Fermi-level effect. An IGa2+ supersaturation also develops because the IGa2+ generation rate is higher than its removal rate. The enhanced SL disordering process mainly proceeds under the Ga-rich SL composition conditions. The Zn-indiffusion-enhanced Al-Ga interdiffusion coefficient shows an apparent dependence on the Zns− concentration differing slightly from a quadratic relationship.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353892
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  • 2
    Electronic Resource
    Electronic Resource
    The influence of ion beam mixed TiSi2 layers on reverse characteristics of diodes (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 4365-4369 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Diodes with shallow p+n junctions were contacted with titanium silicide films which were formed by ion beam mixing with germanium. The leakage current of these diodes was observed to be dominated by a generation mechanism in the space charge layer. Deep level transient spectroscopy and secondary-ion mass spectroscopy measurements revealed that ion beam mixing with heavy ions leads to recoil implantation of titanium atoms into the silicon substrate. The temperature and reverse bias behavior of the leakage current could be consistently explained by Shockley–Read–Hall generation mechanism [Phys. Rev. 87, 385, 387 (1952)] and by Poole-Frenkel barrier lowering [Phys. Rev. 54, 647 (1938)] of the double donor level Ti+/++ at Ev+0.2 eV.4
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350796
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  • 3
    Electronic Resource
    Electronic Resource
    2H-nuclear magnetic resonance study of the host lattice dynamics in the clathrate of Dianin's compound. Concerted rotational jumps of six hydroxyl groups (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 2178-2186 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: 2H-nuclear magnetic resonance was applied to single crystals of the clathrate of Dianin's compound with ethanol as a guest. The hydroxyl groups of both the host lattice and the guest were deuterated. The temperature dependences of the 2H spectra and of the quadrupole coupling tensors of the host lattice deuterons provide evidence that these deuterons carry out jumps between two unequally populated sites. These jumps may be visualized as approximate rotations of the hydroxyl groups about the C–O bonds. The occupancies of the two sites were measured and found to follow a Boltzmann distribution at T〉145 K. At lower temperatures the minority sites are overpopulated. The temperature dependence of the jump rate was determined by line shape analyses and relaxation time measurements. From the absence of dipolar fine structure in the 2H spectra recorded for specially chosen crystal orientations it is concluded that groups of six hydroxyl units carry out their rotational jumps in a concerted manner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458009
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  • 4
    Electronic Resource
    Electronic Resource
    Deuterium two-dimensional exchange nuclear magnetic resonance by rotor-synchronized magic angle spinning (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 7699-7710 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The method of two-dimensional exchange spectroscopy under condition of magic angle sample spinning (MAS) and synchronization of the mixing time with the rotor period is extended to spin I=1 nuclei. Theoretical equations are derived for the cross peak intensities as a function of the magnetic and kinetic parameters of the system and the method is demonstrated on a number of deuterated compounds. Dimethylmalonic acid–d6 is first used to illustrate the effect of rotor synchronization by the complete absence of cross peaks when no exchange takes place. The method is then applied to two dynamic systems, viz. dimethylsulfone–d6 and thiourea–C6D12 inclusion compound. The experimental results are compared with simulations as well as with analogous experiments on nonspinning samples. Since chemical shift effects are often negligible in deuterium NMR the time domain sampling can in principle be reduced to the number of the desired spinning sidebands, resulting in considerable time savings. The main advantage of the method is the gain in sensitivity at the expense of the characteristic ridge pattern of static two-dimensional exchange experiments. The gain in sensitivity may be sufficient for performing such experiments on deuterium in isotopically normal compounds. The feasibility of such experiments is demonstrated by the recording of a one-dimensional deuterium MAS spectrum of a nonenriched sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464578
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  • 5
    Electronic Resource
    Electronic Resource
    Planar diffusion and discrete jumps in pyramidic liquid crystals (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 5927-5938 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Deuterium nuclear magnetic resonance (NMR) spectra are presented for homologues of two series of pyramidic liquid crystals, viz., hexaalkyloxytribenzocyclononatriene, I-n, and hexaalkanoyloxytribenzocyclononatriene, II-n, (where n represents the number of carbon atoms per side chain). The homologues of series I-n exhibit a single hexagonal columnar mesophase PA, while those of series II-n exhibit one or two columnar mesophases (depending on n); a low-temperature biaxial phase PD, and a high-temperature hexagonal phase PC. NMR measurements were performed in the mesophase region on compounds specifically deuterated at the crown methylene groups of the tribenzocyclononatriene core. The spectra in both systems exhibit dynamic features typical of molecules reorienting about their C3 axes within the columnar structures. The experimental spectra were compared with simulated line shapes calculated on the basis of two reorientation mechanisms, (i) symmetric threefold jumps and (ii) planar diffusion about the molecular symmetry axis. It was found that the two compounds of series I-n studied, I-7 and I-10, exhibit spectral line shapes which fit best the planar diffusion model, as was found earlier for the I-8 homologue of this series, while the spectra of the three compounds of series II-n, II-13, II-14, and II-15 are only consistent with the symmetric threefold jump model. Possible reasons for the difference in behavior between the two series are discussed. In an Appendix the asymptotic method for calculating frequency-domain spectra is described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460700
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  • 6
    Electronic Resource
    Electronic Resource
    Trivalent character of platinum in silicon (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 499-501 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A third dominant platinum level is reported. The concentrations of the new level and of the platinum donor level at 0.330 eV above the valence band are equal to each other within 20% over a range exceeding three orders of magnitude in concentration. The new level at approximately 0.067 eV above the valence band is characterized by the method of deep level transient spectroscopy. Its activation energy is shown to be dependent on the electric field. Platinum is suggested to be a double donor in p-type silicon. All three dominant platinum levels are believed to belong to the same platinum center in silicon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104620
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  • 7
    Electronic Resource
    Electronic Resource
    Polarity of (00.1) GaN epilayers grown on a (00.1) sapphire (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 2635-2637 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The polarity is found to be a key parameter for the growth of high quality epitaxial GaN films on sapphire (00.1) substrates. A model is suggested which may consistently explain the observed influence of the process parameters on the polar orientation of the epitaxial film. A simple etching technique is proposed for quick distinction of the film polarity. The assignment of the etching behavior to the proper crystal structure is achieved by an analysis of the respective two-dimensional photoelectron diffraction patterns. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120163
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  • 8
    Electronic Resource
    Electronic Resource
    Diffusion of Fe in InP via the kick-out mechanism (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 75-77 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The diffusion of iron in indium phosphide is found to proceed via the kick-out diffusion mechanism. A Fe diffusion profile in InP available from the literature is simulated using the complete set of three partial differential equations for the kick-out mechanism. A value for the contribution of indium self-interstitials to the self-diffusion coefficient of InP is extracted and found to be much smaller than the known self-diffusion coefficient determined from indium tracer diffusion measurements. Possible reasons for the observed difference are discussed. Furthermore, an analogy of diffusion in InP to diffusion in GaAs is suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108832
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  • 9
    Electronic Resource
    Electronic Resource
    Investigation of the nucleation of oxygen precipitates in Czochralski silicon at an early stage (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 3250-3252 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nucleation of oxygen precipitates in Czochralski silicon is examined in an early stage by measuring vacancy profiles with platinum diffusion. Using an analytical expression, which was deduced from the equations of the Frank–Turnbull diffusion mechanism, the vacancy profiles are calculated from measured platinum diffusion profiles. The vacancy concentration of differently treated Czochralski (CZ) material is compared to the vacancy concentration of float zone (FZ) silicon. In CZ silicon a decrease of the vacancy concentration with increasing nucleation time and platinum diffusion time is found. This decrease cannot be explained by a supersaturation of silicon self-interstitials caused by nucleation and by recombination of self-interstitials and vacancies alone. A direct consumption of vacancies during nucleation also is present. The annihilation rate of the vacancies during nucleation can be estimated to be smaller than 5×108 cm−3 s−1 at 770 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106709
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  • 10
    Electronic Resource
    Electronic Resource
    Pairing of noble metals with phosphorus (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 748-750 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pairing of gold and platinum with phosphorus is examined. For this purpose, gold, respectively platinum, is diffused into silicon wafers, which contained phosphorus doped regions. A value of 1.0×1019 cm−3 at 900 °C is suggested for the equilibrium concentration of gold phosphorus pairs for a phosphorus concentration of 3.0×1020 cm−3. The pair-forming capability of platinum with phosphorus is found to be much smaller. The equilibrium concentration of platinum phosphorus pairs is less than 3×1017 cm−3. Deep level transient spectroscopy measurements show that gold does not penetrate a 14 μm thick phosphorus layer in 2 h and that the platinum concentration in the bulk is a factor of four smaller than in reference samples without phosphorus doping.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106557
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