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  • 1
    Electronic Resource
    Electronic Resource
    Theoretical calculation of impact ionization rate in SiO2 (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1100-1105 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Impact ionization rate in SiO2 was numerically calculated using both pseudo-wave functions and energy band structure based on a self-consistent pseudopotential method. To avoid numerical complexity due to amorphous structure, SiO2 was assumed to be a crystalline α-quartz. The calculated impact ionization rate shows a strong wave vector anisotropy near a threshold energy regime, primary electrons existing at Γ point yield the strongest impact ionization rate. It was found that calculated results are not expressed by a Keldysh formula since SiO2 has complex band structure (e.g., indirect transition gap and nonparabolic bands). The magnitude of the theoretical impact ionization rate was very close to the experimental results recently reported by E. Cartier and F.R. McFeely [Phys. Rev. B 44, 10689 (1991)]. Detailed theoretical study clearly demonstrates that the average energy of secondary generated carriers depends linearly on the energy of primary electrons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354959
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  • 2
    Electronic Resource
    Electronic Resource
    Controlling chaos in the current-driven ion acoustic instability (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 1570-1574 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Control of intermittent chaos caused by the current-driven ion acoustic instability is attempted and the controlling mechanism is investigated. When a small negative dc voltage is applied to the chaotic system as a perturbation, the system changes from a chaotic state to a periodic state while maintaining the instability, indicating that the chaotic state caused by the ion acoustic instability is well controlled by applying a small negative dc voltage. A hysteresis structure is observed on the V–I curve of the mesh grid to which the negative dc voltage to control is applied. Furthermore, when a negative dc voltage is applied to the state which shows a laminar structure existing under same experimental conditions, the system becomes chaotic via a bifurcation. Driven-chaos is excited when a negative dc voltage is applied to the laminar state. Applying a small negative dc voltage leads to controlling intermittent chaos while exciting driven-chaos. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1468232
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  • 3
    Electronic Resource
    Electronic Resource
    Observation of type-1 intermittency caused by current-driven ion acoustic instability (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 401-405 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Intermittent chaotic phenomena caused by the current-driven ion acoustic instability are experimentally observed using a Double Plasma device, in which two mesh grids are installed to excite the instability. When a dc potential is applied to one of the two mesh grids and exceeds a certain threshold, the system suddenly transits from a periodic state to a chaotic state. At the same time, the signals picked up as perturbation components of a current exhibit intermittent turbulent bursts. The calculations of the correlation dimension and the Lyapunov exponent indicate that the system reaches a chaotic state. Furthermore, it is found that the results of mathematical and statistical analysis of observed signals agree with the theoretical properties of the type-1 intermittency: the occurrence of 1/f-type low-frequency noise and the probability distribution of the duration between two bursts. Therefore, it is concluded that the present system reaches a chaotic state via the type-1 intermittency. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872724
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  • 4
    Electronic Resource
    Electronic Resource
    Comparison of resonance conditions in double-barrier structures and triple-barrier structures (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6966-6974 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theoretical analysis has been carried out to compare the resonance condition in the asymmetric double-barrier structure with that in the symmetric triple-barrier one. It is found that the triple-barrier structure may be considered as two quasidouble-barrier structures whose resonance condition may decide the resonance levels in the triple-barrier structure. It is confirmed that two modes exist in the triple-barrier structure: one is normal mode consisting of doublet and the other is degenerated mode of singlet. The critical condition between the two modes is given and its physical meaning is examined. Moreover, it is confirmed that both the normal mode and the degenerated mode exist also in symmetric n-fold barrier structures (n≥3). © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361461
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  • 5
    Electronic Resource
    Electronic Resource
    Perpendicular spin valve behavior in a microstructured Co/Cu-Cu oxide/Co trilayer : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5318-5320 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article we report a perpendicular spin valve behavior in a microstructured noncoupling magnetic trilayer system of Co/Cu-Cu oxide/Co. The Co thin films having markedly different coercivity Hc were prepared with a vacuum evaporation with electron beam (Hc= 20–30 Oe) and rf sputtering (Hc= 90–260 Oe), which enables the selective switching of the magnetization in the base and counter Co layers. The film surface of the Cu was oxidized by the rf sputter etching, which results in the increase of the resistance for the perpendicular current and enables measurements of the perpendicular spin valve behavior at room temperature. The additional spacer layer of sputtered SiO2 with a contact hole of 5 μm diameter was fabricated with photolithographic method between the bottom Co and the intermediate Cu layer, which defined the current path perpendicular to the film plane. The measured magnetoresistance ratio was 0.85% (dR=7.6 mΩ, R=0.89 Ω) at room temperature. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361364
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  • 6
    Electronic Resource
    Electronic Resource
    Impact ionization model for full band Monte Carlo simulation (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 3500-3506 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The impact ionization rate in silicon is numerically derived from wave functions and energy band structure based on an empirical pseudopotential method. The calculated impact ionization rate is well fitted to an analytical formula with a power exponent of 4.6, indicating soft threshold of impact ionization rate, which originates from the complexity of the Si band structure. The calculated impact ionization rate shows strong anisotropy at low electron energy (cursive-epsilon〈3 eV), while it becomes isotropic at higher energy. Numerical calculation also reveals that the average energy of secondary generated carriers depends linearly on the primary electron energy at the moment of their generation. A full band Monte Carlo simulation using the newly derived impact ionization rate demonstrates that calculated quantum yield and ionization coefficient agree well with reported experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356112
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  • 7
    Electronic Resource
    Electronic Resource
    Micromagnetic computation for wall and Bloch line coercivity in thin films with perpendicular anisotropy : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6089-6091 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Wall and vertical Bloch line (VBL) coercivity arising from spatial nonuniformity in the material parameters has been investigated for a typical 5-μm bubble garnet film by means of a two-dimensional micromagnetic computation. Two-dimensional sinusoidal modulations in the magnitude of the uniaxial anisotropy were assumed as a model for a compositional nonuniformity. Nonuniformities with a spatial wavelength comparable to the wall width were found to exert the largest pinning effect. The typical computed value for the wall and VBL coercivity were 0.7 and 2.2 Oe, respectively, where 10% variation and wavelength of 0.47 μm were assumed. The tendency, that the VBL coercivity is larger than that for the domain wall, agrees with the experimental results reported previously. The wall and VBL coercivity caused by a nonuniform exchange constant have also been computed and compared to the analytical solutions due to the step-like variation of wall and VBL energies, respectively. The larger VBL coercivity compared to that for the wall was observed for a local modulation with the size less than wall width and period more than 1 μm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355468
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  • 8
    Electronic Resource
    Electronic Resource
    Micromagnetic study on write operation in submicron magnetic random access memory cell : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6646-6648 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In a spin-valve random access memory, the binary bit states of the storage cell are determined by the magnetization direction in the free magnetic layer. The write operation of a submicron memory cell element has been studied by a micromagnetic computation based on an energy minimization scheme, which aids in the chip design. The magnetization of the binary bit states in the element was found to take a single domain structure having the opposite direction of the long-axis component. The mean long-axis component of magnetization of each binary state was ±0.97 without external fields. The selective switching of the bit state in the element was performed by the write currents applied into the two level conductors overlying the element for various conditions. The influence of the write currents to the neighboring element on a two-dimensional memory array with a 1×1 μm pitch was also simulated, in order to confirm the selective switching of the memory element. It was found that the selective write current amplitude decreased with an increasing assist current amplitude and the range was extended by the large difference of the transverse magnetic field between the selected and neighboring element. The effect of the exchange interaction from the pinned magnetic layer on the write operation was also discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361912
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  • 9
    Electronic Resource
    Electronic Resource
    Impact ionization model for full band Monte Carlo simulation in GaAs (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2473-2480 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The impact ionization rate in GaAs is derived from a first principle's calculation which includes realistic band structure and a wave-vector- and frequency-dependent dielectric function. The impact ionization rate is highly anisotropic at low electron energy, while it becomes isotropic at higher energy range in which impact ionization events frequently occur. The calculated impact ionization rate is well fitted to a modified Keldysh formula with two sets of power exponents of 7.8 and 5.6, indicating very soft threshold characteristics. Using a full band Monte Carlo simulation which includes the empirical phonon scattering rate based on first principles theory, we derived the impact ionization coefficient. The calculated impact ionization coefficients agree well with available experimental data. Our isotropic model shows better agreement with reported experimental data than a previous anisotropic model, especially in low electric field. The mean energy of secondary generated electrons is found to be expressed as two sets of linear functions of the primary electron energy. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361176
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  • 10
    Electronic Resource
    Electronic Resource
    Successive Bloch line write operation in a 1-μM bubble material : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6086-6088 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The successive vertical Bloch line (VBL) write operation has been performed in an as-grown 1-μm bubble material with a flank wall writing scheme. An unwinding VBL pair was nucleated by a domain expanding pulse current (200-mA amplitude, 200-ns pulse width, 8-ns rising edge) applied through a hair-pin type conductor (gap:2.6 μm, width:4 μm). The VBL position was controlled by a local in-plane magnetic field produced by a conductor current of 30 mA and a uniform in-plane magnetic field of 10 Oe. The above operating parameters were adjusted by measuring the collapse field of the stripe domain as a function of the parameters. The increase of bubble collapse field from 442 to 513 Oe in accordance with the number of write operations indicated a successful write operation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355467
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