38 results on '"Ryo Imura"'
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2. An Ultra Small Individual Recognition Security Chip.
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Kazuo Takaragi, Mitsuo Usami, Ryo Imura, Rei Itsuki, and Tsuneo Satoh
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- 2001
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Catalog
3. Influence of hard bubble suppression layer on gate operation in Bloch line memory
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Ryo Imura, Yoji Maruyama, and K. Fujimoto
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Physics ,Annihilation ,Condensed matter physics ,Bubble ,Magnetic storage ,Electronic, Optical and Magnetic Materials ,law.invention ,Magnetization ,law ,Rise time ,Electrical and Electronic Engineering ,Magnetic bubbles ,Antiparallel (electronics) ,Field conditions - Abstract
It is thought that a hard bubble suppression (HBS) layer, which is formed in the path on which magnetic bubbles are propagated in a Bloch line (BL) memory, may have some influence on the gate operation. This influence has been investigated experimentally. We have verified that two types of BLs exist in the HBS area. One type of BL has a Bloch point (BP) in it. The other type of BL has no BP. These two types are classified by the relationship between the magnetization in the HBS area and the magnetization in the BL. The BL with the magnetization antiparallel to the magnetization in the HBS layer has a BP in it, but the BL with the magnetization parallel to the magnetization in the HBS layer has no BP. We have also confirmed that BLs are annihilated when a stripe domain head is shrunk from the HBS area to the non-HBS area. This annihilation depends on the rise time of the pulsed field for shrink and the value of the in-plane field along the long axis of the stripe domain. The BL annihilation during the gate operation in the HBS area cannot be prevented in any field conditions of the practical devices. The stripe domain head should therefore be prevented from going into the HBS area during the gate operation. more...
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- 1996
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4. Vacuum compatible high‐sensitive Kelvin probe force microscopy
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Ryo Imura, Sumio Hosaka, and Atsushi Kikukawa
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Kelvin probe force microscope ,Materials science ,Microscope ,Cantilever ,business.industry ,Resonance ,law.invention ,Optics ,Ion implantation ,law ,Microscopy ,Wafer ,business ,Instrumentation ,Non-contact atomic force microscopy - Abstract
A vacuum compatible Kelvin probe force microscopy (KPFM) is presented. Difficulties in operating KPFM in a vacuum were overcome by utilizing the direct cantilever resonance frequency detection in the tip height control whereas the indirect resonance frequency detection scheme was used in primordial KPFM. The potential measurement sensitivity was improved by 14 dB compared to that in air. It is due to the increased cantilever Q value and the reduction in the interference from the tip height detection signal because potential measurement is conducted using the cantilever’s second resonance while tip height control was conducted using the first resonance. A silicon wafer whose surface is partially doped with arsenic by ion implantation was observed, and surface potential difference at the junctions were clearly imaged. more...
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- 1996
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5. Nanoscale modification of phase change materials with near-field light
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Ryo Imura, Sumio Hosaka, Toshimichi Shintani, and Kimio Nakamura
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Diffraction ,Nanostructure ,Materials science ,business.industry ,Near and far field ,GeSbTe ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Amorphous solid ,law.invention ,chemistry.chemical_compound ,Optics ,chemistry ,Optical microscope ,law ,Near-field scanning optical microscope ,Electrical and Electronic Engineering ,business ,Nanoscopic scale - Abstract
Scanning near-field optical microscope (SNOM) was applied to the formation of ultrasmall phase change domains to investigate the feasibility of ultrahigh density data storage. Phase change domains ranging 60 – 100 nm in diameter, which is far beyond the diffraction limit, could be successfully written in amorphous GeSbTe recording film by point heating with pulsed laser light (λ=785 nm, 7 mW, 0.5 ms) through the optical fiber probe whose aperture size was nearly 50 – 100 nm. The detected power in observation of these recorded domains is 102 – 103 times as high as that in magneto-optical observation. It indicates that phase change recording with SNOM has a potential to achieve ultrahigh density data storage (more than 100 Gb/in2) with high signal detection efficiency. more...
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- 1996
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6. Phase change writing in a GeSbTe film with scanning near-field optical microscope
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Motoyasu Terao, Sumio Hosaka, Kimio Nakamura, Ryo Imura, K. Fujita, Stefan B. Kämmer, Masaru Yoshida, Akemi Hirotsune, and Toshimichi Shintani
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Materials science ,Laser diode ,business.industry ,GeSbTe ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,law.invention ,Amorphous solid ,Phase change ,chemistry.chemical_compound ,Wavelength ,Optics ,chemistry ,Optical microscope ,law ,Near-field scanning optical microscope ,Near field optical microscope ,business ,Instrumentation - Abstract
Scanning near-field optical microscopy (SNOM) was applied to phase-change (PC) mark writing to investigate the potential of ultrahigh density data storage. GeSbTe, one of the typical PC media, was used as a recording layer. Using a laser diode (LD) with a wavelength of 785 nm as light source, crystalline marks with a minimum size of ∼ 80 nm in diameter were successfully written in the amorphous GeSbTe film with pulse conditions of 5 ms and 0.5 ms and 8.4 mW inside the probe. The detected power in observation of the marks was 10 2 –10 3 times as high as that in magneto-optical (MO) observation. more...
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- 1995
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7. Demonstration of nanometer recording with a scanning probe microscope
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Atsushi Kikukawa, Sumio Hosaka, Hajime Koyanagi, Ryo Imura, Mitsuhide Miyamoto, and Toshimichi Shintani
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Materials science ,Cantilever ,Atomic force microscopy ,Nanotechnology ,Condensed Matter Physics ,Information data ,Atomic and Molecular Physics, and Optics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Scanning probe microscopy ,Si substrate ,Nanometre ,Electrical and Electronic Engineering ,Thin film ,Voltage - Abstract
Feasibility of ultrahigh density information data storage has been newly demonstrated by using an atomic force microscope (AFM). Ultrasmall gold dots ranging from 10 to 100 nm in diameter could be successfully recorded on Si substrate in air by adjusting and applied pulsed voltage of AFM probe (SiO"2 birdbeak-type cantilever) coated with gold thin film. It indicates that the technique has a potential to realize a storage density of more than 100 Gb/in^2 and even 1 Tb/in^2. more...
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- 1995
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8. Phase‐locked noncontact scanning force microscope
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Sumio Hosaka, Yukio Honda, Ryo Imura, and Atsushi Kikukawa
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Materials science ,Microscope ,Cantilever ,business.industry ,Phase (waves) ,Signal ,law.invention ,Resonator ,Voltage-controlled oscillator ,Optics ,law ,Control system ,business ,Instrumentation ,Voltage - Abstract
A new tip height control system for noncontact scanning force microscope (SFM) utilizing the phase‐lock technology is proposed. Its most extensive feature is that the system is unconditionally stable whereas the conventional control systems have difficulties in stability especially when the tip is at close proximity to the sample surface. In this new system, an oscillator using the cantilever as a mechanical resonator is used as a voltage controlled oscillator (VCO) in a phase‐locked loop. Its output signal phase is locked to a high precision frequency source. The force gradient detected by the cantilever equivalently alters the VCO control voltage, which is detected as a compensational signal of the loop filter output. The phase‐lock technique made it possible to reduce the tip height to an extent which was impossible with the conventional servo technology. Thus this new control technique is expected to be effective in improving the resolution of the noncontact SFM. more...
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- 1995
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9. Development of a Magnetic Force Microscope Using a Frequency Modulation Technique
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Sumio Hosaka, Yukio Honda, Ryo Imura, and Atsushi Kikukawa
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Scanning Hall probe microscope ,Materials science ,Optics ,business.industry ,Magnetic resonance force microscopy ,Electrical and Electronic Engineering ,Magnetic force microscope ,Condensed Matter Physics ,business ,Instrumentation ,Frequency modulation ,Electronic, Optical and Magnetic Materials - Published
- 1994
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10. Characteristics of Bloch-Line Pair Propagation Using Film Thickness Modulation (FTM) Patterns for Bit Confinement
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K. Fujimoto, Ryo Suzuki, Ryo Imura, and Yoji Maruyama
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Materials science ,Magnetic domain ,Condensed matter physics ,Field (physics) ,Wave propagation ,business.industry ,Magnetic confinement fusion ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Amplitude modulation ,Optics ,Domain wall (magnetism) ,Resist ,Fall time ,Modulation ,Rise time ,Line pair ,Electrical and Electronic Engineering ,Ion milling machine ,business ,Instrumentation - Abstract
A new bit confinement method for Bloch-line (BL) memories which uses film thickness modulation (FTM) has been studied, as a means of making the BL pair propagation common to both sides of the stripe domain wall. Since it is necessary to make the modulation pattern edge smooth for propagation under low driving fields, we used tapered resist patterns for the ion milling mask and carried out the milling to produce a modulation of amplitude 100 nm in an O 2 atmosphere (10?6 Torr). BL pair propagation was tested using a sawtooth pulsed bias field with a 100 ns rise time and a 1000 ns fall time. It was found that the driving field margins did not depend on the propagation direction, because the bit confinement force acts symmetrically on both sides of the domain wall. Furthermore, it was confirmed that the temperature dependence of the driving field margin is larger than that when using the conventional magnetic pattern method. more...
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- 1993
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11. Field evaporation of gold atoms onto a silicon dioxide film by using an atomic force microscope
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Sumio Hosaka, Ryo Imura, Hajime Koyanagi, and Masataka Shirai
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Materials science ,Nanostructure ,Physics and Astronomy (miscellaneous) ,Polarity (physics) ,Silicon dioxide ,business.industry ,Polarity symbols ,Analytical chemistry ,Physics::Optics ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Evaporation (deposition) ,Threshold voltage ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,chemistry ,Elemental analysis ,Optoelectronics ,Spectroscopy ,business - Abstract
To investigate whether field evaporation of gold atoms is responsible for dot formation in an atomic force microscope (AFM) gold‐coated tip/vacuum/SiO2 film/p‐type Si substrate configuration, we have performed elemental analysis of the dots and measured the dependence of the threshold voltage on SiO2 thickness with both polarities for the dot formation. The experiments demonstrate that it is feasible to form gold dots on SiO2 films 17–107 A thick by adjusting the pulsed voltages applied to the gold‐coated AFM tip. Energy dispersive x‐ray spectroscopy (EDX) shows that the dots include gold. The threshold voltages increase almost linearly with the SiO2 thickness. Furthermore, the voltage with negative polarity is lower than that with positive polarity. These results provide evidence that the dot formation on the SiO2 film using AFM occurs by field evaporation. more...
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- 1995
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12. Domain observations of a durability tested TbFeCo magneto‐optical disk using magnetic force microscopy
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Ryo Imura, Yukio Honda, Atsushi Kikukawa, Hiroyuki Awano, and Sumio Hosaka
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Materials science ,Optics ,Physics and Astronomy (miscellaneous) ,business.industry ,Magnetism ,Track (disk drive) ,Microscopic image ,Coercivity ,Magnetic force microscope ,business ,Durability ,Magneto optical ,Magnetic field - Abstract
Complex magnetic structures were observed on a durability tested TbFeCo magneto‐optical disk. By considering the magnetic properties of the TbFeCo and the polarized microscopic image of the same region, it was concluded that those complex structures result from the decrement of the compensation temperature of the TbFeCo film at the track center. Samples that were exposed to static magnetic fields were also observed for the purpose of inspecting the changes in the coercive force of the damaged regions. more...
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- 1995
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13. Silicon pn junction imaging and characterizations using sensitivity enhanced Kelvin probe force microscopy
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Atsushi Kikukawa, Ryo Imura, and Sumio Hosaka
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Kelvin probe force microscope ,Cantilever ,Physics and Astronomy (miscellaneous) ,business.industry ,Chemistry ,Electrostatic force microscope ,Analytical chemistry ,Atomic force acoustic microscopy ,Microscopy ,Optoelectronics ,p–n junction ,business ,Non-contact atomic force microscopy ,Photoconductive atomic force microscopy - Abstract
We observed the surface potential of silicon pn junctions using a Kelvin probe force microscope whose sensitivity was about five times better than that of a conventional one. It was achieved by three major improvements: electrostatic force detection using the second cantilever resonance, cantilever Q‐value enhancement by operating in a vacuum, and direct cantilever resonance frequency detection using the frequency modulation technique. It was demonstrated that the surface potential of the pn junctions made by thermal diffusion varies gradually compared to those made by ion implantation, possibly reflecting their gradual dopant concentration profile. more...
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- 1995
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14. Ultrahigh density data storage by atomic manipulation
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Mitsuhide Miyamoto, Toshimichi Shintani, Kimio Nakamura, Ryo Imura, Sumio Hosaka, Hajime Koyanagi, and Atsushi Kikukawa
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Materials science ,Magnetic domain ,business.industry ,Magnetism ,Optical engineering ,Laser ,law.invention ,Optics ,Optical microscope ,law ,Computer data storage ,Near-field scanning optical microscope ,Thin film ,business - Abstract
Feasibility of ultrahigh density information data storage has been newly demonstrated by using an atomic force microscope (AFM) and a scanning near-field optical microscope (SNOM). Ultrasmall gold dots about 20 to 80 nm in diameter could be stably formed on Si substrate in air by adjusting an applied pulsed voltage of AFM probe coated with gold thin film. Magnetic domains about 60 to 80 nm in diameter also could be successfully recorded on magneto optical disk material (Pt/Co multilayer) by controlling a writing pulsed laser power of sharp fiber probe with SNOM. These indicate that this technique has a potential to realize a storage density of more than 100 Gb/in2 and even 1 Tb/in2.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. more...
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- 1994
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15. Nanometer recording using an atomic force microscope
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Ryo Imura, Atsushi Kikugawa, Sumio Hosaka, and Hajime Koyanagi
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Materials science ,Cantilever ,Silicon ,Silicon dioxide ,chemistry.chemical_element ,Nanotechnology ,Substrate (electronics) ,engineering.material ,Local oxidation nanolithography ,chemistry.chemical_compound ,Coating ,chemistry ,engineering ,Nanometre ,Layer (electronics) - Abstract
We demonstrated the feasibility of ultrahigh-density storage by using an atomic force microscope in air to form gold dots tens of nanometers in diameter on a silicon substrate. The probe was prepared by coating a thin gold film onto a SiOg birdbeak-type cantilever fabricated by a silicon microprocess. Gold dots about 15 to 200 nm in diameter could be successfully formed by controlling the applied pulsed voltage between the probe and a silicon substrate covered with a layer of natural silicon dioxide. These results indicate that this technique can be used for recording information at a density greater than 1 Trillion-bit/in2. more...
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- 1994
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16. Ultra High Density Data Storage by Atomic Manipulation
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Ryo Imura, Hajime Koyanagi, Mitsuhide Miyamoto, Toshimichi Shintani, Kimio Nakamura, Atsushi Kikukawa, and Sumio Hosaka
- Abstract
Nanometer and atomic scale surface modification using scanning probe microscopes is a new and promising method to store data with ultra high densities [1]-[3]. It is expected that this technique has the potential to achieve a storage density of more than 100 Gb/in2 and even 1 Tb/in2. Advances in storage techniques using several local probe methods such as tunneling, force and near-field optical microscopes have been reported recently. One of the most simple way is to form ultra small pits or dots on a substrate by means of field evaporation of tip surface atoms. Another method is related to the switching phenomena similar to conventional magneto-optical disk memories and by using a sharp tip to heat a point area of the storage medium. more...
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- 1994
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17. Thermal Simulation Analysis of Scanning Near-Field Optical Microscope Point Heating Mechanisms
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Miyamoto, Mitsuhide, primary, Shintani, Toshimichi, additional, Sumio Hosaka, Sumio Hosaka, additional, and Ryo Imura, Ryo Imura, additional
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- 1996
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18. Bloch Line Pair Propagation With New Self-organized Memory Cell
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Y. Maruyama, K. Fujimoto, and Ryo Imura
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Physics ,Temperature control ,Nuclear magnetic resonance ,Magnetic domain ,Condensed matter physics ,Memory cell ,Magnet ,Magnetic films ,Line pair ,Lithography ,Electrical conductor - Published
- 1993
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19. Phase Controlled Scanning Force Microscope
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Kikukawa, Atsushi, primary, Hosaka, Sumio, additional, Honda, Yukio, additional, and Ryo Imura, Ryo Imura, additional
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- 1994
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20. Thermal Simulation Analysis of Scanning Near-Field Optical Microscope Point Heating Mechanisms
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Mitsuhide Miyamoto, Sumio Hosaka, Toshimichi Shintani, and Ryo Imura
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Nanostructure ,Chemistry ,business.industry ,General Engineering ,Physics::Optics ,General Physics and Astronomy ,GeSbTe ,Thermal diffusivity ,Thermal conduction ,Ray ,law.invention ,chemistry.chemical_compound ,Optics ,Optical microscope ,law ,Near-field scanning optical microscope ,sense organs ,Thin film ,business - Abstract
We performed thermal simulation of nanostructure modifications through point heating of phase-change materials using a scanning near-field optical microscope (SNOM). As the recording process, two major heating mechanisms were considered: direct heating by near-field light and thermal conduction from the SNOM tip heated by the incident light. The temperature increases in the sample due to these heating mechanisms were calculated for GeSbTe phase-change thin films. It was found that thermal conduction from the tip was the dominant process for heating and its temperature increase was more than three times larger than that of direct heating by near-field light. more...
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- 1996
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21. Magnetic and electrical properties of single-phase, single-crystal Fe16N2 films epitaxially grown by molecular beam epitaxy (invited)
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Yutaka Sugita, Ryo Imura, Matahiro Komuro, Takashi Kambe, Hiromasa Takahashi, and Masukazu Igarashi
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Magnetization ,Materials science ,Magnetic moment ,Condensed matter physics ,Hall effect ,Electrical resistivity and conductivity ,General Physics and Astronomy ,Epitaxy ,Ferromagnetic resonance ,Single crystal ,Molecular beam epitaxy - Abstract
The average magnetic moment per Fe atom for a single‐phase, single‐crystal Fe16N2(001) film epitaxially grown on a GaAs(001) substrate by molecular beam epitaxy has been confirmed to be 3.5μB at room temperature by using a vibrating sample magnetometer (VSM) and Rutherford backscattering. The value was in good agreement with that obtained by using a VSM and by measuring the film thickness (3.3μB per Fe atom). The saturation magnetization 4πMs has been found to increase with decreasing temperature, obeying T3/2 law at lower temperatures. The slope was steeper than that of a pure Fe film, suggesting a lower exchange constant for Fe16N2. The g factor for Fe16N2 has been accurately measured to be 2.17 by using ferromagnetic resonance with changing frequencies of 35.5–115 GHz, which is not unusual compared with the g factor of 2.16 for pure Fe. The resistivity for Fe16N2 has been measured to be around 30 μΩ cm at room temperature compared with 10 μΩ cm for pure Fe and decreases linearly with decreasing tempera... more...
- Published
- 1996
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22. High density data storage with a SNOM
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Atsushi Kikukawa, Ryo Imura, Sumio Hosaka, and Toshimichi Shintani
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Materials science ,business.industry ,Computer data storage ,Optoelectronics ,High density ,Near-field scanning optical microscope ,Electrical and Electronic Engineering ,Condensed Matter Physics ,business ,Instrumentation ,Electronic, Optical and Magnetic Materials - Published
- 1996
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23. Depth and State Analyses of Deuterium and Helium in D2-Annealed He+-Implanted Yttrium Iron Garnet
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Kenichi Matsushita, Ryo Imura, Keiichi Furuya, Michi Aratani, Minoru Yanokura, and Kenichi Uematsu
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Annealing (metallurgy) ,Radiochemistry ,General Engineering ,Thermal desorption ,Yttrium iron garnet ,Analytical chemistry ,General Physics and Astronomy ,chemistry.chemical_element ,Mass spectrometry ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,Ion implantation ,chemistry ,Deuterium ,Physics::Atomic and Molecular Clusters ,Physics::Atomic Physics ,Surface layer ,Nuclear Experiment ,Helium - Abstract
Simultaneous depth analysis of deuterium and helium in the surface layer of deuterium-annealed He+-implanted yttrium iron garnet (YIG) was achieved by means of elastic recoil depth analysis (ERDA) and the results were compared with those of state analysis of deuterium and helium extracted by thermal desorption mass spectrometry (TDS). As a result, it was shown that both deuterium and helium moved to the strained lattice sites due to implantation via thermal annealing of the samples. By annealing the critically helium-saturated sample, helium atoms remained at the stable sites in the lattice, while deuterium occupied the less stable sites. Stabilization of helium sites at annealing temperature of around 350° C was observed for unsaturated and critically saturated samples. In the case of an oversaturated sample, three kinds of sites for helium were found, and it was observed that helium formed bubbles and that deuterium concentrated at sites corresponding to those of helium via annealing. more...
- Published
- 1995
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24. Phase Controlled Scanning Force Microscope
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Atsushi Kikukawa, Sumio Hosaka, Ryo Imura, and Yukio Honda
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Cantilever ,Chemistry ,business.industry ,Instrumentation ,General Engineering ,Phase (waves) ,General Physics and Astronomy ,Signal ,Phase-locked loop ,Resonator ,Scanning probe microscopy ,Voltage-controlled oscillator ,Optics ,business - Abstract
A noncontact scanning force microscope employing a novel tip height control system using phase lock technology has been developed. An oscillator using a cantilever as a mechanical resonator is used as a voltage controlled oscillator in a phase locked loop, and its output signal is phase locked to a high-precision signal source. Its most remarkable feature is that this tip height control is unconditionally stable. Thus, it was possible to realize the desired system response by adjusting the loop parameters. Its efficiency was demonstrated by imaging the surface of a magneto-optical disk at the lowest tip height which was impossible to achieve with a conventional servo technology. more...
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- 1994
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25. Interpretation of magnetic force microscopic images (abstract)
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Atsushi Kikukawa, Ryo Imura, Yukio Honda, Sumio Hosaka, and Hiroyuki Awano
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Kelvin probe force microscope ,Physics ,Cantilever ,Optics ,Magnetic resonance microscopy ,business.industry ,General Physics and Astronomy ,Magnetic resonance force microscopy ,Atomic force acoustic microscopy ,Magnetic force microscope ,business ,Non-contact atomic force microscopy ,Magnetic field - Abstract
The authors have developed a magnetic force microscope (MFM) which works in a vacuum. By detecting the cantilever resonance frequency directly, it takes full advantage of the improved cantilever resonance quality, lowered noise level, and improved resolution, due to reduction of the air resistance that the cantilever suffers. Detailed observations on various magnetic recording media were made employing this instrument. An obstacle in interpreting the MFM images is that they contain both the magnetic image and the surface corrugation (directly related to the atomic force) since the cantilever detects both magnetic and atomic force at the same time. One solution for this is to compare the images of the same region observed at different tip to sample spacings because the contrast due to the magnetic force decreases as the tip to sample spacing reduces. We confirmed that this decrement in magnetic contrast occurs due to the effects of the atomic force by predicting the MFM image theoretically, utilizing a mod... more...
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- 1994
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26. Thermal Extraction Behavior of He and D from He+-Implanted Yttrium Iron Garnet Annealed in D2
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Kimihiko Masuda, Ryo Imura, Kenichi Uematsu, Keiichi Furuya, Tadashi Kikuchi, and Akemi Hirotsune
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Hydrogen ,Annealing (metallurgy) ,General Engineering ,Analytical chemistry ,Thermal desorption ,Yttrium iron garnet ,General Physics and Astronomy ,chemistry.chemical_element ,Mineralogy ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,Ion implantation ,chemistry ,Density of states ,Thin film ,Helium - Abstract
Thermal extraction behavior of He and D from He+-implanted yttrium iron garnet (Y3Fe5O12 or YIG) thin films annealed in D2 and activation energies of He and D in each trapping state have been investigated by means of a thermal desorption mass spectrometric (TDS) technique in order to clarify the effect of hydrogen on the effective anisotropy field change induced by ion implantation followed by D2 annealing. Four trapping states of He in He+-implanted YIG were observed when it was annealed under T a=320°C at a constant pressure of 760 Torr. The residual He atoms shifted to stabler states when it was annealed at above T a=350°C. Two trapping states of diffused D atoms which were extracted as a form of D2O were observed for two kinds of YIG samples annealed in D2 atmosphere. The relationship between effective anisotropy field change induced by ion implantation and the thermal extraction behavior of He and D was discussed against the annealing temperature. more...
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- 1993
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27. Bloch line propagation with film thickness modulation bit patterns (abstract)
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Ryo Imura, K. Fujimoto, Y. Maruyama, and R. Suzuki
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Amplitude ,Optics ,Materials science ,business.industry ,Power consumption ,Bubble ,General Physics and Astronomy ,Ion milling machine ,business ,Anisotropy ,Bias field ,Saturation (magnetic) - Abstract
Bloch line (BL) propagation with a field‐access scheme is necessary for the memory with low power consumption and high storage density. Previously we reported the field‐access propagation using Co‐Pt bit patterns.1 In these propagation patterns, (a) the drive field margins depend on the BL propagating direction to the magnetized direction of Co‐Pt patterns and (b) the operating bias field margins are different at each corner of the stripe domain. The purpose of this paper is to solve these two problems. A new propagation method has been investigated using film thickness modulation patterns.2 The materials used here were magnetic bubble garnet films with composition of (YSmLuCa)3(FeGe)5O12. Fundamental characteristics of the samples are as follows: saturation induction 4πMs 200 G, anisotropy field Hk 1700 Oe, stripe width w and thickness h 5 μm. The thickness modulation patterns with an amplitude of about 1000 A were fabricated with the ion milling method. The stripe domains were stabilized around the 100%... more...
- Published
- 1991
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28. Depth Profiling of Hydrogen Implanted into Magnetic Bubble Garnet Films Using the 1H(15N, αγ)12C Reaction
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E. Arai, Yu Byoung-gon, and Ryo Imura
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chemistry.chemical_classification ,Hydrogen ,Bubble ,General Engineering ,Analytical chemistry ,General Physics and Astronomy ,chemistry.chemical_element ,Magnetic anisotropy ,Ion implantation ,Nuclear magnetic resonance ,chemistry ,Irradiation ,Thin film ,Anisotropy ,Inorganic compound - Abstract
Using the 1H(15N, αγ)12C reaction, we have realized a high-resolution profiling of depth distribution of hydrogen implanted into the magnetic bubble garnet (MBG) films. The experimental results are compared with predictions from the Monte-Carlo simulation code (TRIM85). We have investigated two phenomena by observing the thermal behavior of hydrogen in the MBG films: 1) the efficiency of the SiO2 layer deposited onto the MBG film to suppress the hydrogen out-diffusion and 2) the effect of plasma exposure on MBG films that have been predamaged by Ne irradiation. We have obtained useful knowledge to achieve a large anisotropy field change that plays an important role for the production of the magnetic bubble memory devices with high storage density. New features are reported to understand the thermal behavior of hydrogen in the MBG films. more...
- Published
- 1991
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29. Hydrogen Extraction Activation Energy from D2 +-Implanted Magnetic Bubble Garnet
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Hisamitsu Suzuki, Tadashi Kikuchi, Ryo Imura, Kenichi Uematsu, Keiichi Furuya, and Jae Soo Shin
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Hydrogen ,General Engineering ,Thermal desorption ,Analytical chemistry ,General Physics and Astronomy ,chemistry.chemical_element ,Activation energy ,Mass spectrometry ,Epitaxy ,Overlayer ,Deuterium ,chemistry ,Impurity ,Nuclear chemistry - Abstract
Deuterium in D2 +-implanted magnetic garnet films was extracted by means of thermal desorption mass spectrometry and found to be a form of D2O at 360°C in vacuo. The overall activation energy for extraction was measured as 1.62 eV for D2O and 1.04 eV for DHO. The effect of the SiO2 overlayer was also discussed. more...
- Published
- 1990
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30. A method for high sensitivity deuterium measurements by means of the D(3He, p)4He reaction and its applications
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Q. Qiu, Michi Aratani, Ryo Imura, Tadashi Nozaki, Minoni Yanokura, Yuzuru Ohji, and E. Arai
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Nuclear and High Energy Physics ,Hydrogen ,Chemistry ,Annealing (metallurgy) ,Solid angle ,Oxide ,Analytical chemistry ,chemistry.chemical_element ,Scintillator ,Nitrogen ,chemistry.chemical_compound ,Deuterium ,Gate oxide ,Instrumentation - Abstract
High sensitivity measurement of deuterium in solids has been realized using the D( 3 He, p) 4 He reaction. A large annular plastic scintillator is adopted to cover a solid angle of 1.45 π sr for detection of 14-MeV protons from the reaction. Deuterium was used to simulate hydrogen chemistry in solids. The ultimate sensitivity in our experiment was limited to 7 × 10 12 at. cm −2 by the interference with natural deuterium in the surface hydrogen. Setting the goal as the improvement of MOS gate oxide reliability, this technique has been adopted to investigate the behavior of very low concentration of deuterium (7 × 10 16 –10 19 cm −3 ) in thin SiO 2 layers. The experimental results show that: (1) a significant amount of D 2 O has been diffused into ultradry oxide layer of SiO 2 from D 2 O ambient even at 200 ° C and (2) the deuterium content has been decreased by annealing in dry nitrogen at above 700 ° C. more...
- Published
- 1989
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31. Design and operation of a high-speed bubble memory board
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Toyooka Takashi, Hirokazu Aoki, Mamoru Sugie, Ryo Imura, Shigeru Yoshizawa, Yutaka Sugita, and Kazuhiro Ishida
- Subjects
Dynamic random-access memory ,Engineering ,Hardware_MEMORYSTRUCTURES ,Computer Networks and Communications ,business.industry ,Sense amplifier ,Electrical engineering ,Phase margin ,Memory controller ,law.invention ,Memory module ,Memory bank ,law ,Electronic engineering ,Bubble memory ,Electrical and Electronic Engineering ,Memory refresh ,business - Abstract
A magnetic memory board was designed and an experimental model was constructed for evaluation of its characteristics. the memory board contains eight 256 kb memory chips with an 8 μm cycle and operates with a rotating magnetic frequency of 312.5 kHz. These chips are driven by an already-developed single-chip memory module and a high-speed rotating magnetic field drive circuit. to improve the peripheral circuits with respect to speed, reliability and size, several circuits were developed, including the transformer-coupled pulse-current generator for the functional part of the chip, the sense circuit with a high-sensitivity comparator, and the high-speed defect loop skip circuit using ROM and a shift resistor. the eight memory modules and their peripheral circuits were implemented on a 24.5 × 48.5 cm memory board. the circuits were adjusted and an examination was made of the defect loop detection and the operational margin, which indicated that stable operation was possible. Evaluation of the experimental memory board over a temperature range of 10° to 45° showed that the bias margin is larger than ±5 Oe, the rotating magnetic field amplitude margin is larger than ±6 Ue, and the pulse current phase margin is greater than ±150 as. the memory board was applied to the 64 Mb file in the database machine. more...
- Published
- 1983
- Full Text
- View/download PDF
32. Ion-implanted and permalloy hybrid magnetic bubble memory devices
- Author
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Umezaki Hiroshi, Yutaka Sugita, Ryo Imura, T. Satoh, Teruaki Takeuchi, Ryo Suzuki, Naoki Kodama, M. Takeshita, Tadashi Ikeda, and Naoki Koyama
- Subjects
Permalloy ,Hardware_MEMORYSTRUCTURES ,Materials science ,business.industry ,Detector ,Electronic, Optical and Magnetic Materials ,Ion ,Ion implantation ,Hardware_INTEGRATEDCIRCUITS ,Numerical control ,Bubble memory ,Optoelectronics ,Electrical and Electronic Engineering ,business ,Swap (computer programming) ,Electrical conductor - Abstract
Hybrid bubble memory devices have been proposed and operated with the memory density of 4 Mbit/cm2. In the hybrid bubble memory devices, minor loops are composed of ion-implanted tracks with 4-µm period, and major lines and functional parts including block-replicate and swap gates are composed of Permalloy tracks with a longer period of 12 µm. Passive junctions between ion-implanted and Permalloy tracks have been developed, introducing the tapered ion-implantation technique. Improving the characteristics of the functional parts composed of Permalloy tracks, the hybrid bubble memory devices with block-replicate and swap gates have been operated, and the feasibility of the devices has been confirmed. In addition, the possibility of higher memory density has been shown. more...
- Published
- 1986
- Full Text
- View/download PDF
33. Spin Glass State of MnxNi1-xSb: Synthesis in High Pressure and High Temperature Atmospheres
- Author
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Ryo Imura, Kengo Adachi, Masaaki Matsui, and Hiroshi Sawamoto
- Subjects
Paramagnetism ,Spin glass ,Materials science ,Condensed matter physics ,Transition point ,Ferromagnetism ,Electrical resistivity and conductivity ,Phase (matter) ,General Physics and Astronomy ,Absolute zero ,Solid solution - Abstract
The solid solution between ferromagnetic MnSb and paramagnetic NiSb, Mn x Ni 1- x Sb (0≤ x ≤1.0), with NiAs structure was synthesized in high pressure and high temperature atmospheres. The decomposition temperature was determined to be 420∼480 K. The critical concentration of ferromagnetism was obtained to be x c =0.65 at absolute zero. A new type spin glass state with double transition points, T sg1 and T sg2 , was found in a wide range of 0.2≤ x ≤0.65 in the paramagnetic phase. The maximum transition point was estimated to be T sg1 =60 K and T sg2 =190 K. The electrical resistivity showed no anomaly corresponding to T sg1 and T sg2 , and the temperature dependence in the spin glass state was given to be T 2 and T 3/2 at lower temperature. Some discussions are given for the experimental results. more...
- Published
- 1978
- Full Text
- View/download PDF
34. Garnet crystals for magnetic bubbles
- Author
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Ryo Imura
- Subjects
Materials science ,Condensed matter physics ,Magnetic bubbles ,Garnet crystals - Published
- 1986
- Full Text
- View/download PDF
35. Quasistatic Bubble Propagation in 1.5 μm Period Ion-Implanted Tracks for 64 Mbit Magnetic Bubble Memory Devices
- Author
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Umezaki Hiroshi, Ryo Suzuki, Naoki Koyama, Toshihiro Sato, Toyooka Takashi, Yuzuru Hosoe, and Ryo Imura
- Subjects
Materials science ,business.industry ,Bubble ,STRIPS ,Temperature measurement ,law.invention ,Optics ,Resist ,law ,Reticle ,Bubble memory ,business ,Layer (electronics) ,Quasistatic process - Abstract
Ion-implanted tracks with a 1.5 μm period for use in 64 Mbit magnetic bubble memory devices have been fabricated and operated. The bubble material used was (BiSmLu) 3 (FeAl) 5 O 12 garnet film, supporting 0.45 μm bubbles. The resist mask patterns for implantation were formed using a 1/10 reduction projection aligner, using rectangular patterns on a reticle. The bubble propagation tracks were fabricated by double deuterium implantation and annealed at 400°C for 30 minutes, with an SiO 2 layer deposited on the garnet surface to stabilize the implanted layer. An operating bias field margin in excess of 7% was stably obtained in quasistatic bubble propagation. This shows that the ion-implanted devices have great potential for use in 64 Mbit magnetic bubble memory devices. more...
- Published
- 1989
- Full Text
- View/download PDF
36. Annealing Effects in Heavily Ion-Implanted Magnetic Bubble Garnet Films
- Author
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Ryo Imura, Tadashi Ikeda, and Yutaka Sugita
- Subjects
Materials science ,Annealing (metallurgy) ,Bubble ,General Engineering ,Analytical chemistry ,General Physics and Astronomy ,Mineralogy ,Anisotropy ,Ion - Abstract
Anomalous increase of the effective anisotropy field change Δ(H K-4πM S) has been found when magnetic bubble garnet films were heavily implanted with Ne+/He+ and subsequently annealed at high temperatures (350°C). With annealing, Δ(H K-4πM S) increases with annealing time, reaches a maximum value and then decreases. Δ(H K-4πM S) vs. strain (Δ a/a) does not follow the curve for as-implanted films. Δ(H K-4πM S) has reached up to 3700 Oe which is 1200 Oe larger than that expected for as-implanted films (2500 Oe). This anomalous increase has been observed only for films whose initial strain is more than about 1.5%; the effect has not been observed in heavily H+ 2 implanted films. more...
- Published
- 1984
- Full Text
- View/download PDF
37. 4460412 Method of making magnetic bubble memory device by implanting hydrogen ions and annealing
- Author
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Tadashi Ikeda, Umezaki Hiroshi, Teruaki Takeuchi, Yutaka Sugita, Nagatugu Koiso, Ryo Imura, and Ryo Suzuki
- Subjects
Materials science ,Condensed matter physics ,Hydrogen ,Annealing (metallurgy) ,chemistry.chemical_element ,Mineralogy ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Ion ,Monocrystalline silicon ,Condensed Matter::Materials Science ,chemistry ,Physics::Plasma Physics ,Condensed Matter::Superconductivity ,Bubble memory ,Anisotropy ,Magnetic bubbles ,Instrumentation - Abstract
A method of implanting a magnetic garnet film with ions is disclosed in which a covering film is provided on a monocrystalline magnetic garnet film for magnetic bubbles, and hydrogen ions are implanted in a desired portion of a surface region in the magnetic garnet film through the covering film. According to this method, it is possible to form an ion-implanted layer in which the ion concentration distribution in the direction of depth is uniform, and moreover the inplane anisotropy field in the ion-implanted layer decreases only a little with time in an annealing process. more...
- Published
- 1985
- Full Text
- View/download PDF
38. A method for high sensitivity deuterium measurements by means of the D( 3He, p) 4He reaction and its applications
- Author
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Qi Qiu, Eiichi Arai, Michi Aratani, Minoni Yanokura, Tadashi Nozaki, Yuzuru Ohji, and Ryo Imura
- Published
- 1989
- Full Text
- View/download PDF
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