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  • 1
    Electronic Resource
    Electronic Resource
    Effects of annealing, using a plasma-excited chemical vapor deposition SiN film as a cap, on the carrier density of AlGaAs/GaAs heterostructures and Si-doped GaAs (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4401-4406 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigate how the mobility and carrier density of AlGaAs/GaAs two-dimensional electron gas are influenced by the fabrication process with plasma-excited chemical vapor deposition (plasma-CVD) SiN film. These properties are greatly reduced by annealing with plasma-CVD SiN film as a cap but are restored by reannealing after removing the SiN film. We further use capacitance-voltage measurements to investigate the influence of this same process on a more simplified structure, Si-doped GaAs layer. Annealing with a plasma-CVD SiN film changes the defect density of Si-doped GaAs in two, temperature dependent ways: annealing below 380 °C reduces deposition damage, and annealing above 300 °C produces new defects, which might be caused by the film stress. These new defects can be reduced by reannealing after removing the SiN film. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359846
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  • 2
    Electronic Resource
    Electronic Resource
    1.3 μm InAsP compressively strained multiple-quantum-well lasers for high-temperature operation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 4119-4121 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-temperature operation of InAsP-based laser diodes at 1.3 μm has been realized according to guidelines of a large conduction-band-offset material (ΔEc) with a large optical confinement factor (Γ). Using photoluminescence excitation spectroscopy measurements, it was found that the conduction-band offset of InAs0.52P0.48P/InGaAsP is the half of the band-gap energy difference (0.5 ΔEg), which is larger than that of conventional quaternary material systems. A strain-compensation growth technique enabled the fabrication of a large number of wells for large Γ. For broad-area laser diodes, the maximum operating temperature increased as the number of wells increased from 4 to 15. In buried heterostructure lasers with ten wells, with high-reflectivity coating on both facets, continuous-wave lasing operation at temperatures up to 150 °C was achieved with a characteristic temperature of 59 K (30〈T〈70 °C) demonstrating the suitability of InAsP for high-temperature operation. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359497
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  • 3
    Electronic Resource
    Electronic Resource
    Electrical transport properties and confinement potential analysis of buried AlGaAs/GaAs quantum wires (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2330-2335 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Buried wires with lateral potential barriers provided by AlGaAs/GaAs heterointerfaces have been fabricated by wet etching and metalorganic chemical vapor deposition regrowth. Burying the wire was proven to enhance the electrical transport properties; for example, it decreased the critical width and increased the subband energy separation. Two-dimensional simulation using the Poisson equation was performed to obtain the potential profile of both as-etched and buried wires. The quantum energy levels corresponding to the lateral confinement were calculated for the obtained potential profiles. The calculated energy separations agreed well with the experimental ones and the subband energy separation of the buried wire was larger than that of the as-etched wire for the same effective width. These results show that burying wire is effective for creating strong lateral confinement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357605
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  • 4
    Electronic Resource
    Electronic Resource
    Time-resolved optical waveguide study of the reorientation in a nematic liquid crystal under applied electric field (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 1135-1142 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The reorientation behavior of nematic liquid crystal molecules induced by an electric pulsed field was investigated by means of time-resolved optical waveguide spectroscopy (TROWS) which was developed to observe transient changes in dielectric constants and to measure the thickness of a thin dielectric medium. Time evolution of the waveguide mode patterns was successfully obtained by using TROWS, which records the reflectivity as both functions of the incident angle of laser light and the time from switching-on or -off of the external electric field. The transient dielectric tensor profile in the 4′-pentyl-4-cyanobiphenyl (5CB) layer both after switching-on and -off of the electric field could be precisely determined in a three-dimensional coordinate system by using Deuling's theory which treats the orientational deformation induced by an external electric field. Theoretical analysis of TROWS data clearly indicated that half of the 5CB molecules rotate clockwise in the plane defined by the rubbing direction and the substrate normal, and the other half rotates counter-clockwise in the same plane. The counter rotation compensates the effect of birefringence observed in the direction parallel and perpendicular to the rubbing direction and the reorientation kinetics could be well described by the Ericksen–Leslie equation. Relaxation behavior from homeotropic to planar orientation could be treated as an orientation diffusion process by applying a Gaussian distribution function to the maximum tilting angle at the middle of the cell. We report the usefulness of TROWS which provided more detailed information about the dynamics of the 5CB molecules. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363859
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  • 5
    Electronic Resource
    Electronic Resource
    Polyphase eddy current testing : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 5904-5906 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polyphase eddy current testing is proposed. The operating principle of this system is as follows. The polyphase eddy current testing system may be regarded as one of the polyphase transformers. Primary balanced polyphase coils are star connected and secondary polyphase circuits are composed of the target. When balanced polyphase currents are fed into the primary coils, zero phase voltage is detected if the target has defects. No zero phase voltage is detected if the target has no defects. It is found that this method has a higher sensitivity compared with that of conventional eddy current testing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355557
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  • 6
    Electronic Resource
    Electronic Resource
    Laser-induced fluorescence spectroscopy for the determination of the absolute density and spatial distribution of Si atoms in a SiH4-He-Ar glow discharge (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1050-1054 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the absolute density and the spatial distribution of silicon atoms in a SiH4-He-Ar dc glow discharge measured by the laser-induced fluorescence method. The absolute sensitivity of the fluorescence-photon-counting system was calibrated by using the same system to measure Rayleigh scattering by Ar gas in the discharge chamber. The fluorescence quantum efficiency and the polarization degree of emitted light were measured to confirm the absence of excited-state quenching induced by collisions with the buffer-gas atoms. The measured spatial distribution profile of the ground-state silicon atoms is compared with that of the excited-state atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342476
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  • 7
    Electronic Resource
    Electronic Resource
    Controlling garnet film composition by magnetic-field-controlled radio frequency magnetron sputtering (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6776-6778 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: To find a way to control the compositional change in Bi-substituted garnet during sputtering, we studied the effects of controlling the cathode magnetic field. The magnetic-field-controlled rf magnetron sputtering method that we developed can create a garnet film whose composition is the same as that of the sputtering target. When we deposited a film of Bi-substituted Dy iron garnet–ferrite (Bi2DyFe4GaO12) by this method, there was no compositional change between the target and the film even after a long sputtering process. Therefore, this sputtering method is effective at suppressing compositional change during the film formation process. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372838
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  • 8
    Electronic Resource
    Electronic Resource
    Status of the HIMAC pulsed Penning source : The 8th international conference on ion sources (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 972-974 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Since 1994 at the National Institute of Radiological Sciences HIMAC, the NIRS Penning ionized-gauge ion source (PIGIS) has so far been used for radiotherapy with carbon beams and for basic research with several ion species. The source can produce beams from H2 to Fe with a charge-to-mass ratio of between 1/7 and 1/2. It is a hot-cathode type with a filament, of which the lifetime is on the order of a week and the cathode on the order of 1 month, under a low-duty pulsed operation (≤0.5%) synchronized to the ring operation. This PIGIS can produce highly charged ions: for example, 1 e mA of Ar7+ or 500 eμ A of Si5+ ions (by sputtering) under the typical arc power of 5 kW in peak. This article describes the present status of the NIRS-PIGIS. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150362
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  • 9
    Electronic Resource
    Electronic Resource
    Longitudinal impedance tuner using new material FINEMET (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 2988-2992 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We designed an impedance tuner consisting of an inductive material, FINEMET, to cancel the space charge impedance in the longitudinal direction. It was installed in the KEK Proton Synchrotron (PS) main ring. We observed the frequency shift of the coherent quadrupole oscillations and inferred the shift of the incoherent synchrotron oscillation. The total reactive impedance can be estimated as the coefficient between the shift and the beam intensity. The measured impedance is reduced from −j2475Ω to −j1182Ω by the impedance tuner which consists of 12 pieces of FINEMET cores. We demonstrated that the space charge impedance is compensated by the impedance tuner. This is the first time for FINEMET to be equipped with an accelerator component. One may think that the characteristics of FINEMET deteriorate under an environment with strong radiation generated by unavoidable beam loss. We have proved that the radiation dose not affect FINEMET even with a total neutron dose of 1.83×1012(n cm−2), which is considered to be the highest dose of the main ring. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149859
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  • 10
    Electronic Resource
    Electronic Resource
    Status of ion sources for the Heavy Ion Medical Accelerator HIMAC : Proceedings of the 6th international conference on ion sources (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 962-964 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Heavy Ion Medical Accelerator in Chiba (HIMAC) at National Institute of Radiological Sciences (NIRS) is the first heavy-ion accelerator complex dedicated to cancer therapy. HIMAC is equipped with two kinds of ion sources. The PIG ion source is an indirectly heated cathode type, which is operated with a very low-duty factor. The ECR ion source has a single closed ECR zone with 10 GHz microwaves. Both sources realize good stability and reproducibility with easy operation, and satisfy the requirements for radiotherapy. They have been successfully used for clinical trials since June of 1994, and several tens of cancer patients have already been treated with 290–400 MeV/u carbon beams. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146784
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