Mitsuhide Miyamoto

Nanometer-sized Phase-Change Recording using a Scanning Near-Field Optical Microscope with a Laser Diode.

We present for the first time a nanometer-sized phase-change recording using a scanning near-field optical microscope (PC-SNOM recording). The recording experiments were performed with a SNOM using a 785-nm-wavelength semiconductor laser diode, shear force detection for gap control and reflected light detection for observing the domains (reading). The recording media of ZnSSiO2(20 nm)/GeSbTe(30 nm)/ZnSSiO2(150 nm)/polycarbonate substrate were used. The writings were done at laser powers of 8.4–7.3 mW in the probe for pulse widths of 5 or 0.5 ms. As a result, we obtained a minimum recorded domain size of 60 nm in diameter. This size shows a potential to achieve an ultrahigh density PC-SNOM recording with about 170 Gb/in2. A possibility of achieving high speed readout for the future data storage is also discussed.

Phase change recording using a scanning near‐field optical microscope

The formation and observation, with reflected light, of 60‐nm‐diam phase‐changed domains in a thin GeSbTe film using a scanning near‐field optical microscope with a 785 nm wavelength laser diode is demonstrated. The dependence of the domain size on incident laser power was obtained, and the size changed from 150 to 60 nm in diameter with incident power of 8.4–7.3 mW in the probe. At the threshold power of 7.3 mW, the film temperature rose to around 180 °C to partially phase change the local area of the film from amorphous to crystalline. A detected reflectivity increase due to phase change in the formed domain was 8%–2%. The observing (reading) was performed with an incident laser power of 0.2 mW, which corresponds to 10−2–10−3 times less than in a magneto‐optical recording. The incident laser power shows that the phase change reading using the reflection scanning near‐field optical microscope has the potential to read the recorded bit at a speed over 10 MHz.

SPM-based data storage for ultrahigh density recording

The possibility of SPM-based data storage is described regarding both its recording density and readout speed for ultrahigh density data storage. We consider their gap control to achieve high-speed readout. Suitable SPM-based storages are selected and their details are studied. As a result, scanning near-field optical microscope (SNOM)- and atomic force microscope (AFM)-based storages are expected to be candidates for future storage. SNOM-based storage is for . AFM-based storage is for . Using new force modulation AFM pit recording, an ultrahigh recording density of and a readout speed of are demonstrated.

HIGH-DENSITY THERMOMAGNETIC RECORDING METHOD USING A SCANNING TUNNELING MICROSCOPE

A new thermomagnetic recording method using tunneling current in a scanning tunneling microscope as a heating source is proposed. In the experiment, pulse voltage of from 2–8 V with a pulse width of 1 ms is applied to the sample, while the probe position is kept at a bias voltage of 0.2 V and a tunneling current of 0.3 nA. As a result, we have demonstrated that thermally recorded magnetic domains are formed in a Pt/Co multilayered film and minimum domains as small as 0.2 μm in diameter are observed using a polarized optical microscope.

Scanning near-field optical microscope with a laser diode and nanometer-sized bit recording

We demonstrate 80 nm diameter bit recording for the first time using a phase change recording film and a reflection scanning near-field optical microscope with a 785 nm wavelength laser diode. The sample structure was a 20 nm thick ZnS-SiO 2 protection layer/30 nm thick Ge 2 Sb 2 Te 5 recording film/150 nm thick ZnS-SiO 2 protection layer/polycarbonate substrate. Writing was performed with pulsed laser light of 8.4 mW for 5 ms and 0.5 ms, and 8.0 mW for 5 ms. Written bits were observed in reflection by illuminating a small light of 0.2 mW. In this form of recording, a formation of phase change domains of about 50 nm in diameter is expected if the surface deformation is suppressed. Our results indicate the possibility to achieve an ultra-high recording density of more than 100 Gb in -2 .

Analysis of mark-formation process for phase-change media

The objective of this study was to determine the mechanism of a phenomenon peculiar to phase-change recording regarding the mark shape or mark-forming process. The following results were obtained from our simulation of mark shapes, transparency electron microscope observations, and analysis of reproduced signals. A method of calculating a mark shape by calculating the holding-time profile was devised and its appropriateness was confirmed. We found there were close relationships between the cooling pulse shape, the effective erase ratio, the reproduced signal amplitude, and the noise level, and that the temperature change when the mark edge was cooled has a great influence on the stability of the mark shape and crystallized regions.

XY stages driving an electron beam mastering system for high density optical recording

Abstract XY stages driving an electron beam (EB) mastering system for high density optical recording has been designed and prototyped. This system has some unique techniques for subnanometer accuracy, i.e. super-polygon approximation for spiral writing, auto focus adjusting, highly precise position-detecting, and a 32-bit data format. The system demonstrated fine pits writing with a small size of 50×80 nm and an accuracy of position of about 1.6 nm ( σ ) in a rotation direction. We confirmed that the mastering system can be applied to fabrication of 40 Gb/in 2 fine pit patterns. Furthermore, this system has the potential to write a fine pit pattern of over 100 Gb/in 2 .

Force modulation atomic force microscopy recording for ultrahigh density recording

We propose force modulation atomic force microscopy (FM)-(AFM) pit recording and demonstrate the possibility of achieving ultrahigh density recording with high speed readout. A minimum pit size of around 10 nm in diameter is formed by cold plastic deformation of the polycarbonate disk surface at a force of over 40 nN. Using a prototype of the rotation type FM-AFM pit recording system, an ultrahigh recording density of 1.2 Tb/in.2 and a readout speed of 1.25 Mb/s are demonstrated in 1/2(2,7) code recording.

High-Speed Programming Architecture and Image-Sticking Cancellation Technology for High-Resolution Low-Voltage AMOLEDs

We have developed a high-speed programming architecture and an image-sticking cancellation technology that utilize a pixel circuit with only four TFTs for LTPS active-matrix organic light-emitting-diode (OLED) displays. High-speed programming is realized through controlled-amplitude precharging. The gate voltage of the drive TFT in data programming converges the fixed voltage on very low voltage and very short programming time by controlled-amplitude precharging. This means that an image-lag-free picture can be achieved on a low-power high-resolution display. Image-sticking cancellation is realized by detecting the OLED anode voltage difference between neighboring pixels. When there is a large amount of OLED characteristic shading over an entire panel, it is difficult to detect the absolute value of the OLED characteristic to judge image sticking. Therefore, detecting the OLED difference between neighboring pixels is useful. A 3.0-in 202 × 267 ppi full-color panel was developed. This panel could produce image-lag-free pictures at low-voltage (4-V) operation because of high-speed programming, and we confirmed that image sticking could be detected and canceled by the proposed cancellation technology.

Fabrication of nanometer‐scale structures on insulators and in magnetic materials using a scanning probe microscope

Field evaporation and electron induced local heating in scanning probe microscopes [atomic force microscope, scanning tunnel microscope (STM), and magnetic force microscope (MFM)] are investigated for a nanometer‐sized structure fabrication on an insulator and for a fine magnetic domain formation in a magnetic material. Application of negative voltage to the gold‐coated AFM probe can be provided to make gold lines 40 nm wide and dots 20 nm in diameter on SiO2/Si by field evaporation. Reversely, in a positive voltage, thermal processes are dominant, one of which is the formation of nanometer‐sized magnetic domains produced by electron induced local heating using STM and MFM. The proposed MFM recording can form 60×240 nm2 domains in a Pt/Co multilayer magnetic film and they can be observed with the same probe.