Photorefractive damage, photoconductivities, and photogalvanic currents of LiNbO3 single crystals have been investigated as a function of [Li]/[Nb] and MgO concentrations. Near stoichiometric LiNbO3 single crystal, having large [Li]/[Nb] ratios of 0.993, shows lower photorefractive damage resistance than congruent LiNbO3. However, crystals doped with a small amount of MgO (>0.78 mol %) exhibit no measurable photorefractive damage at 532 nm to intensities of as much as 2 MW/cm2. This remarkable decrease of photorefraction that was found can be attributed to the decrease of saturated space charge field results from a combination of the increased photoconductivity and the decreased photogalvanic current of the crystal.
Semiconductor blue-multi-laser-diode annealing (BLDA) for amorphous Si film was performed to obtain a film containing uniform polycrystalline silicon (poly-Si) grains as a low temperature poly-Si (LTPS) process used for thin-film transistor (TFT). By adopting continuous wave (CW) mode at the 445 nm wavelength of the BLDA system, the light beam is efficiently absorbed into the thin amorphous silicon film of 50 nm thickness and can be crystallized stably. By adjusting simply the laser power below 6 W with controlled beam shape, the isotropic Si grains from uniform micro-grains to arbitral grain size of polycrystalline phase can be obtained with reproducible by fixing the scan speed at 500 mm/s. As a result of analysis using electron microscopy and atomic force microscopy (AFM), uniform distributed micro-poly-Si grains of smooth surface were observed at a power condition below 5 W and the preferred crystal orientation of (111) face was confirmed. As arbitral grain size can be obtained stably and reproducibly merely by controlling the laser power, BLDA is promising as a next-generation LTPS process for AM OLED panel including a system on glass (SoG).
Phase-change random access memory (PRAM) technology is reviewed. PRAM uses the phase change between the amorphous state and the crystalline state caused by Joule heating as its memory mechanism. A change in electrical resistance owing to a phase change is detected by a small electric current. The merits of this approach are that the resistance change is more than one order of magnitude, and its simple structure decreases the number of steps in the manufacturing process. Suppression of reset current for the change from the lowresistance crystalline state to the amorphous state and an improvement in durability against set-reset cycles and high-temperature operation will ultimately be achieved.
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.
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