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  • 1
    Digitale Medien
    Digitale Medien
    Extremely low non-alloyed specific contact resistance ρc (10−8 Ω cm2) to metalorganic molecular beam epitaxy grown super heavily C-doped (1021 cm−3) p++GaAs (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 8227-8232 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The specific contact resistance ρc of non-alloyed ohmic metals (Mo/Au and WSix) to p-type GaAs is evaluated by transmission line method (TLM) patterns for various doping concentrations from 8×1018 to 1021 cm−3. The obtained specific contact resistance ρc, less than 10−8 Ω cm2, to metalorganic molecular beam epitaxy grown C-doped ( 1021 cm−3) GaAs is the lowest reported value. From the application point of view for the emitter electrodes of PNp type (two-dimensional electron gas base) heterojunction bipolar transistors, the specific contact resistance of a refractory metal, or the sputter-deposited WSix (x=0.45), is also studied. By reducing the growth temperature of molecular beam epitaxy from 600 to 450 °C and enhancing the As4/Ga flux ratio to 15, a nondiffusive heavily Be doped (1020 cm−3) GaAs is obtained. The specific contact resistance of the WSix to this sample is less than 10−6 Ω cm2. The obtained specific contact resistance can be well explained by a simple modeling based on the tunneling transport of light holes. Secondary ion mass spectroscopy analysis of the depth profile under heat acceleration shows a small diffusion of dopants for Be doped (1020 cm−3) GaAs and C-doped (1021 cm−3) GaAs. In addition, the specific contact resistance ρcISO of the isoheterojunction (p+GaAs/p+AlxGa1−xAs) is also evaluated by TLM patterns.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.347427
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  • 2
    Digitale Medien
    Digitale Medien
    Ionization by electron impact in an indirectly heated Penning source (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 151-154 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: ion-production mechanism in an indirectly heated Penning source has been studied at NIRS. Taking the number of primary electron passages between two cathodes into account, we calculated the effective electron current density, Ji ; it is the order of kA/cm2 for Ar, where the index "i'' is the charge state. In a pulsed arc condition of 2.6 A and 1300 V with a neutral atom density of 4×1013/cm3(cw), the calculated ionization times for Ar5+→Ar6+ and Ar6+→Ar7+ are 18 and 28 μs if their production process is step-by-step. These values agree well with the experimental value of 20 μs. Ji is proportional to the arc voltage and inversely proportional to the neutral-atom density N. The yield of multiply charged ions is in proportion to 1/Ni−2. This expression agrees well with the experimental results, which suggest that multiply charged ions are produced from Ar2+ through step-by-step ionization by primary electrons.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.347736
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  • 3
    Digitale Medien
    Digitale Medien
    Application of low-temperature ions in the nonequilibrium state plasma of a Penning source (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 7933-7935 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We present the high-output properties during the early 100–200 μs of a pulsed Penning source. The peak intensity, I, is higher than that of a dc source by a factor of more than 10. This phenomenon is due to the long confinement time of ions, τ, at the rising of the plasma, since within such a short time the ion temperature, T, does not reach thermal equilibrium and is still low. These characteristics are expressed as I∝τ∝T−1/2. The ratio of T−1/2 before and after equilibrium has a maximum of 1/18.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.347487
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  • 4
    Digitale Medien
    Digitale Medien
    Influence of electronic states on precipitation of metallic As clusters in LT-GaAs (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 6016-6020 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The influence of electronic states of the semiconductor matrix on the precipitation of metallic As clusters in GaAs epilayers grown by molecular beam epitaxy at low temperatures were studied. From x-ray diffraction and Hall effect measurements, the presence of free carriers was found to occur in a certain time after the start of the coarsening stage of the precipitation. Transmission electron microscope observations indicate that redistributions of As clusters between the doped and undoped regions starts at the same time with the appearance of free carriers. Redistributions of As clusters occurs in pn junction structures in such a way that depletion zones of the pn junctions become free from As clusters, leading to close correlation of widths of precipitate free zones with those of the depletion zones of the pn junctions for various dopant concentrations. These observations are explained with a tendency of As metal clusters of reducing free carriers in the surrounding semiconductor matrix and hence keeping it as an intrinsic semiconductor. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1319324
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  • 5
    Digitale Medien
    Digitale Medien
    Construction and beam experiment of a compact storage ring at MELCO : Proceedings of the 5th international conference on synchrotron radiation instrumentation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 1968-1970 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A compact storage ring has been developed for industrial research such as x-ray lithography and material analysis. This machine is of a racetrack type with two superconducting bending magnets and only two normal conducting quadrupole magnets. The circumference is as short as 9.2 m. One quadrupole magnet per cell contributes to making the smaller machine. The injector is a synchrotron, and a full energy injection of 600 MeV is performed. The bending magnets excite a field of 3.5 T, and are operated in a persistent current mode. A decrease in a coil current is ΔI/I〈3×10−3/year. The helium consumption is as low as 2 l/h for two magnets. An iron shield of the magnet decreases a leakage flux to a terrestrial level at a point 3 m from the magnet. A beam current of 380 mA has been stored with no beam instability in spite of there being no correction of the chromaticities. Beam emittances were obtained from measured beam sizes and were in good agreement with calculated values. The coupling coefficient εy/εx is calculated as around 0.04. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1145772
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  • 6
    Digitale Medien
    Digitale Medien
    Development of the National Institute of Radiological Sciences electron cyclotron resonance ion source for the heavy ion medical accelerator in Chiba : Proceedings of the 5th international conference on ion sources (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1087-1089 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: The development of an electron cyclotron resonance ion source for the heavy ion medical accelerator in Chiba (HIMAC) injector is reported. The HIMAC is a heavy ion medical accelerator for cancer therapy. The electron cyclotron resonance (ECR) ion source is expected to provide a long lifetime, easy operation, and easy maintenance for medical use. The NIRS-ECR ion source has a single closed ECR stage, and a microwave frequency of 10 GHz is applied. Under the present performance, the output electrical currents of the ions are 2500 eμA for He1+, 300 eμA for C2+, 480 eμA for Ne3+, and 110 eμA for Ar6+. Stability of the intensity is better than 2%. The transmission efficiency through a low-energy beam-transport line with an acceptance of 200 πmm mrad is more than 70%; the typical 50% and 90% emittances of the injection beam with 8 keV/u are 20 and 80 πmm mrad, respectively. These performances satisfy the requirements for radiotherapy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1145071
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  • 7
    Digitale Medien
    Digitale Medien
    Retrospective review of 41 patients with endodermal sinus tumor of the ovary (1993)
    238 Main Street, Cambridge, Massachusetts 02142, USA : Blackwell Scientific Publications
    International journal of gynecological cancer 3 (1993), S. 0 
    Details
    ISSN: 1525-1438
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Forty-one patients with endodermal sinus tumors of the ovary (EST) (23: pure EST, nine: EST with dysgerminoma; and nine: EST with immature teratoma) were treated with cytoreductive surgery, with or without subsequent adjuvant chemotherapy including VAC or PVB. Clinical staging of these patients showed 23 in stage I, six in stage II and 12 in stage III and IV. The outcome was good in the patients with stage I or II disease, with 5- and 10-year survival rates of around 80%. In contrast, all except two patients with stage III or IV disease died within 2 years. Aggressive surgery did not change the outcome of patients with stage I disease. In addition, postoperative chemotherapy was necessary, but the choice of vincristine, actinomycin-D and cyclophosphamide (VAC) or cis-platin, vinblastine and bleomycin (PVB) did not make any difference. Based on the results of the present study, VAC or PVB chemotherapy, after cytoreductive surgery, is essential for cure and conservative surgery followed by VAC or PVB regimen should be recommended for young patients.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1525-1438.1993.03050329.x
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  • 8
    Digitale Medien
    Digitale Medien
    Causes of low seed set in white clover (Trifolium repens L.) (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Grass and forage science 48 (1993), S. 0 
    Details
    ISSN: 1365-2494
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: A field experiment was conducted to clarify the factors responsible for poor seed set in four white clover (Trifolium repens L.) cultivars. Although the mean number of ovules per floret was 5·18–5·29, the average number of seeds per floret was found to be only 1·23-1·82. A stainclearing technique was used to examine the cytoplasmic state of the embryo sac in intact, unfertilized, mature ovules and it was found that 28–33% of ovules per carpel were sterile. The abortion rate of fertilized ovules and immature seeds (7 days after pollination) ranged between 32 and 34%. Beyond this period, it was observed that only a very small proportion of the total seeds were lost. The observation of high pollen fertility and a high pollen load strongly suggests that poor pollination does not account for the reduced number of seeds per floret. A ‘nutrient competition’ hypothesis was proposed for high ovule sterility and post-fertilization abortion of developing seeds.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2494.1993.tb01839.x
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  • 9
    Digitale Medien
    Digitale Medien
    Propagation and reflection properties of magnetoelastic wave in FeSiB amorphous wire : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4653-4655 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Propagation and reflection properties of magnetoelastic waves in Fe77.5Si7.5B15 amorphous wires are studied. The attenuation constant increases with increasing the driving frequency of the wave. As the attenuation constant of the wave driving at 500 kHz is quite small (0.18 m−1), the wave is expected to be observed after the propagation of 20 or 30 m. As for the reflection, the magnetoelastic wave is reflected with the efficiency as much as 0.9 at the driving frequency below 2 MHz using a clamp as reflector. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.361694
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  • 10
    Digitale Medien
    Digitale Medien
    Measurements of magnetization dynamics and magnetoimpedance in FeCoSiB and FeSiB amorphous 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. 6542-6544 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A technique to observe magnetization dynamics in amorphous wires is described. When an ac current passes through the amorphous wire, voltages induced between both ends of the wire and in a pickup coil wound around the wire are observed. These voltages indicate circumferential and axial components of magnetization changes in the wire, respectively. Observations in a Co-rich wire having slightly negative magnetostriction and an Fe-rich wire having positive magnetostriction under various bias fields showed quite different wave forms which indicate their domain structure. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.361940
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