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  • 1
    Electronic Resource
    Electronic Resource
    Hydrogen in amorphous and microcrystalline silicon films prepared by hydrogen dilution (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 4971-4975 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hydrogen incorporation in silicon layers prepared by plasma-enhanced chemical-vapor deposition using silane dilution by hydrogen has been studied by infrared spectroscopy (IR) and elastic recoil detection analysis (ERDA). The large range of silane dilution investigated can be divided into an amorphous and a microcrystalline zone. These two zones are separated by a narrow transition zone at a dilution level of 7.5%; here, the structure of the material cannot be clearly identified. The films in/near the amorphous/microcrystalline transition zone show a considerably enhanced hydrogen incorporation. Moreover, comparison of IR and ERDA and film stress measurements suggests that these layers contain a substantial amount of molecular hydrogen probably trapped in microvoids. In this particular case the determination of the total H content by IR spectroscopy leads to substantial errors. At silane concentrations below 6%, the hydrogen content decreases sharply and the material becomes progressively microcrystalline. The features observed in the IR-absorption modes can be clearly assigned to mono- and/or dihydride bonds on (100) and (111) surfaces in silicon crystallites. The measurements presented here constitute a further indication for the validity of the proportionality constant of Shanks et al. [Phys. Status Solidi B 110, 43 (1980)], generally used to estimate the hydrogen content in "conventional'' amorphous silicon films from IR spectroscopy; additionally, they indicate that this proportionality constant is also valid for the microcrystalline samples. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363541
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  • 2
    Electronic Resource
    Electronic Resource
    Ambipolar diffusion length and photoconductivity measurements on "midgap'' hydrogenated microcrystalline silicon (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 5111-5115 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hydrogenated microcrystalline silicon (μc-Si:H) deposited by VHF plasma-enhanced chemical vapor deposition has recently been proven to be fully stable, with respect to light-induced degradation, when adequately used in p-i-n solar cells. Stable solar cells efficiencies of 7.7% have been obtained with single-junction cells, using "midgap'' microcrystalline i-layers, having an optical gap of around 1 eV. In the present paper, the electronic transport properties of such microcrystalline layers are determined, by the steady-state photocarrier grating method (SSPG) and steady-state photoconductivity measurements, in a coplanar configuration. The conditions for the validity of the procedure for determining the ambipolar diffusion length, Lamb, from SSPG measurements (as previously theoretically derived in the context of amorphous silicon) are carefully re-examined and found to hold in these μc-Si:H layers, taking certain additional precautions. Otherwise, e.g., the prevalence of the "lifetime'' regime (as opposed to the "relaxation time'' regime) becomes questionable, in sharp contrast with the case of amorphous semiconductors, where this condition is almost never a problem. For the best layers measured so far, Lamb is about twice as high and the photoconductivity σphoto four times as high in μc-Si:H, when compared to device quality a-Si:H. Until now, the highest values of Lamb found by the authors for μc-Si:H layers are around 3×10−5 cm. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363491
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetic properties of nanosized wires : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6010-6012 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Assemblies of ferromagnetic cylinders made of Ni with diameters ranging from 35 to 250 nm were produced by electrodeposition in nanoporous membranes. The large coercive fields of Ni nanowires at low temperature could be accounted for by the curling mode of magnetization reversal, taking into account the distributions of wire diameters and orientations. The coercive field of the nanowires of the smaller diameter range decreased from 1500 Oe at 20 K to 200 Oe at 300 K nearly linearly. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362136
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  • 4
    Electronic Resource
    Electronic Resource
    Electrical properties and degradation kinetics of compensated hydrogenated microcrystalline silicon deposited by very high-frequency-glow discharge (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 712-716 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Microcrystalline silicon (μc-Si:H) layers deposited by the very high-frequency-glow discharge technique at a radio-frequency excitation of 70 MHz are observed to be basically slightly 〈n〉 type. By doping (so-called "microdoping'') with boron in the gas phase volume part per million (vppm) range, compensated material could be obtained. The influence of this doping on the electronic transport properties is documented. A pronounced onset of the boron incorporation into the films measured by secondary-ion-mass spectrometry is observed around 3 vppm (B2H6/SiH4), together with marked changes in the electrical properties. The compensated film obtained for a microdoping of about 1 vppm shows the lowest dark conductivity [3×10−8 (Ω cm)−1], the highest activation energy (517 meV), and, finally, the highest photoconductive gain of 6×103 (photo/dark current ratio). Depending on the value of the activation energy (the critical value is ≈0.2 eV), two different transport models are identified, corresponding to "Meyer–Neldel'' or "anti-Meyer–Neldel'' behavior. As for light-induced degradation, the compensated film exhibits better stability than undoped films. Finally, the use of slightly boron doped μc-Si:H as photovoltaically active material will be discussed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358992
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  • 5
    Electronic Resource
    Electronic Resource
    Recoil implantation of radioactive transition metals and their investigation in silicon by deep-level transient spectroscopy (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2370-2372 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Radioactive isotopes are produced by nuclear reactions in a thin target foil. The recoiling products are directly implanted into samples mounted off-axis to the primary beam. Using proton or α beams and appropriate target foils, radioactive isotopes of Ti, V, Cr, Mn, and Co were implanted. The implantation parameters are presented and compared with other implantation techniques for radioactive isotopes. To demonstrate an application, a deep-level transient spectroscopy measurement on 48V in silicon is presented. Ti and V correlated band-gap levels were observed during the 48V decay. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113986
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  • 6
    Electronic Resource
    Electronic Resource
    Device grade microcrystalline silicon owing to reduced oxygen contamination (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 1373-1375 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: As-deposited undoped microcrystalline silicon (μc-Si:H) has in general a pronounced n-type behavior. Such a material is therefore often not appropriate for use in devices, such as p-i-n diodes, as an active, absorbing i layer or as channel material for thin-film transistors. In recent work, on p-i-n solar cells, this disturbing n-type character had been successfully compensated by the "microdoping'' technique. In the present letter, it is shown that this n-type behavior is mainly linked to oxygen impurities; therefore, one can replace the technologically delicate microdoping technique by a purification method, that is much easier to handle. This results in a reduction of oxygen impurities by two orders of magnitude; it has, furthermore a pronounced impact on the electrical properties of μc-Si:H films and on device performance, as well. Additionally, these results prove that the unwanted donor-like states within μc-Si:H are mainly due to extrinsic impurities and not to structural native defects. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117440
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  • 7
    Electronic Resource
    Electronic Resource
    The Association Behavior of Polystyryllithium, Polyisoprenyllithium, and Polybutadienyllithium in Hydrocarbon Solvents (1970)
    s.l. : American Chemical Society
    Macromolecules 3 (1970), S. 327-332 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma60015a011
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  • 8
    Electronic Resource
    Electronic Resource
    Electrophysiological Performance of a Bipolar Membrane-Coated Titanium Nitride Electrode: A Randomized Comparison of Steroid and Nonsteroid Lead Designs (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Pacing and clinical electrophysiology 22 (1999), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The aim of this multicenter study was to investigate the performance of a new cardiac pacemaker lead with a titanium nitride cathode coated with a copolymer membrane. In particular, the electrophvsiological effect of steroid dissolved in this ion-exchange membrane was evaluated by randomized comparison. Ninety five patients were randomized either to the 1450 T (n = 51) or the 1451 T ventricular lead (n = 45) and received telemeteral VVI(R) pacemakers with identical diagnostic features. Both leads were bipolar, were passively affixed, and had a porous titanium nitride tip with a surface area of 3.5 mm2. The only difference between the two electrodes was 13 μg of dexamethasone added to the 1450 Ts membrane coating. Voltage thresholds (VTH) at pulse durations of 0.25, 0.37, and 0.5 ms, lead impedance, and sensing thresholds were measured at discharge, 2 weeks, 1 month, 3 months, and 6 months after implantation. Mean amplitude and the slew rate from three telemetered intracardiac electrograms, clironaxie-rheobase product, and minimum energy consumption were calculated. After a 6-month follow-up, mean voltage thresholds of 0.65 ± 0.20 V and 0.63 ± 0.34 were achieved for the 1450 T lead and 1451 Tlead, respectively. As a result, a VTH 〈 1.0 V was obtained in all patients with 1450 T electrodes and in 97.7% of patients with 1451 T leads after 6 months follow-up. In both electrodes, stable VTH was reached 2 weeks after implantation, and no transient rise in threshold was observed. No differences were observed between the steroid and the nonsteroid group in respect to VTH, chronaxie-rheobase product, minimum energy consumption, and potential amplitude and slew rate. In conclusion, safe and efficient pacing at low pulse amplitudes were achieved with both leads. The tip design, independently of the steroid additive, prevented any energy-consuming increases in the voltage threshold.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1999.tb06818.x
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  • 9
    Electronic Resource
    Electronic Resource
    Intraoperative Gamma Detection Of125I-Lanreotide in Women With Primary Breast Cancer (1999)
    Springer
    Annals of surgical oncology 6 (1999), S. 367-372 
    Details
    ISSN: 1534-4681
    Keywords: Somatostatin receptors ; Gamma radiation ; Breast cancer ; Somatostatin analogs ; 125Iodine.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: Somatostatin receptors are present in most human breast cancers. We performed a pilot trial of intraoperative tumor-gamma detection using the radiolabeled somatostatin analog 125I-lanreotide in 13 women with 14 primary breast carcinomas. Methods: All patients were given125I-lanreotide intravenously before surgery. Patients underwent lumpectomy, and postresection margins were evaluated with the gamma probe. Axillary dissection specimens were evaluated ex vivo. Results: Seven of 13 women had gamma probe-positive or clinically suspicious margins reexcised at the time of lumpectomy. Four of six probe-positive margins were histologically positive, and two of six probe-positive margins were histologically negative; a single clinically suspicious margin was histologically positive. A total of 270 axillary lymph nodes were evaluated ex vivo by gamma probe and histology. McNemar’s contingency tests demonstrated a highly statistical correlation between histology and gamma probe counts (P 〈 .0001). Conclusions: The overall accuracy of nodal evaluation with125I-lanreotide/intraoperative gamma detection was 77%; the negative predictive value of this technique was 97%, however. This technique predicted the presence of tumor in 20% of axillary lymph nodes that were negative by routine histology. This technique appears safe and is able to detect positive tumor resection margins and accurately predict axillary lymph node negativity. Further trials of this technique are required to validate its utility.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10434-999-0367-y
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  • 10
    Electronic Resource
    Electronic Resource
    Higher generation subgroup sets and the $ \Sigma $-invariants of graph groups (1998)
    Springer
    Commentarii mathematici Helvetici 73 (1998), S. 22-44 
    Details
    ISSN: 1420-8946
    Keywords: Key words. Graph groups, $ \Sigma $-invariants, finiteness properties and n-generating subgroup sets.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract. We present a general condition, based on the idea of n-generating subgroup sets, which implies that a given character $ \chi \in \rm {Hom}(G, \Bbb {R}) $ represents a point in the homotopical or homological $ \Sigma $ -invariants of the group G. Let $ \cal {G} $ be a finite simplicial graph, $ \widehat {\cal {G}} $ the flag complex induced by $ \cal {G} $ , and $ G \cal {G} $ the graph group, or 'right angled Artin group', defined by $ \cal {G} $ . We use our result on n-generating subgroup sets to describe the homotopical and homological $ \Sigma $ -invariants of $ G \cal {G} $ in terms of the topology of subcomplexes of $ \widehat {\cal {G}} $ . In particular, this work determines the finiteness properties of kernels of maps from graph groups to abelian groups. This is the first complete computation of the $ \Sigma $ -invariants for a family of groups whose higher invariants are not determined - either implicitly or explicitly - by $ \Sigma $ 1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000140050044
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