Naoko Asakuma

Bio: Naoko Asakuma is an academic researcher from Arkema. The author has contributed to research in topics: Thin film & Amorphous solid. The author has an hindex of 7, co-authored 11 publications receiving 1181 citations.

Crystallization and Reduction of Sol-Gel-Derived Zinc Oxide Films by Irradiation with Ultraviolet Lamp

Abstract: Structural changes in sol-gel films with photo-irradiation were investigated using zinc oxide (ZnO) derived from zinc acetate. The exposure of the films to an ultraviolet lamp induced hexagonal ZnO crystals in a relatively dense amorphous structure. On the other hand, the formation of zinc metal was found in a porous gel film. The photo-induced crystallization and reduction are ascribed to the electronic excitation in the metastable non-crystalline states.

Ultraviolet-reduced reduction and crystallization of indium oxide films

Abstract: Structural changes stimulated by ultraviolet (UV) irradiations of sol–gel-derived indium oxide thin films were investigated. Illumination of incoherent UV photons (4.9 eV) from a low-pressure mercury lamp resulted in formation of crystalline indium metal. Irradiation of coherent UV beams from an ArF excimer laser (6.4 eV) and from the fourth harmonics of a Nd:YAG laser (4.7 eV) was found to be effective in the crystallization of indium oxide, accompanied by a decrease in the sheet resistance. The lowest resistance without a reduction of transmission in the visible region was achieved with a 6.4 eV laser beam at a fluence over 10–20 mJ cm−2 shot−1. The results of x-ray photoelectron spectroscopy revealed that charge transfer from O2− to In3+ was induced by the incoherent and the coherent UV photons. The partial reduction with the incoherent illumination and the crystallization with the laser irradiation are tentatively assumed to be due to electronic excitations in the amorphous network.

Low-Temperature Synthesis of ITO Thin Films Using an Ultraviolet Laser for Conductive Coating on Organic Polymer Substrates

Abstract: The resistivity of sol-gel-derived indium tin oxide (ITO) films effectively decreased with crystallization by exposure to a low fluence UV beam (10–20 mJ/cm2) from an ArF laser. The increase in temperature at the surface of the films was below 10°C under the irradiation condition. Thus, conductive and transparent ITO coatings were successfully obtained on polyethylene terephthalate and polyimide sheets using a sol-gel route assisted with an ultraviolet laser beam.

Photocrystallization of amorphous ZnO

Abstract: Structural changes stimulated by UV light irradiation for sol-gel-derived amorphous ZnO were investigated. Transformation of amorphous ZnO into the wurtzite phase was achieved by irradiation of 4.9 eV photons in air using a conventional low-pressure mercury lamp. On the other hand, the crystallization was not observed by UV irradiation in vacuum. Cleavage of the Zn–O network with electronic excitation and subsequent oxidation with activated oxygen species are deduced to be essential for the formation of the ordered structure from the amorphous phase.

Effects of introduction of sodium and water on second-order nonlinearity in poled synthetic silica glass

Abstract: Second harmonic generation (SHG) from silica glasses doped with sodium or water was investigated to clarify the effects of the impurities on the second-order nonlinearity. Sodium ions were introduced into pure silica glasses from a polymer coating containing a trace amount of sodium with electrical poling. The doping of sodium drastically increased the SHG intensity from the poled silica glasses. The nonlinearity localized in the anode surface region is suggested to be ascribed to a frozen electric field formed by the drift of sodium ions. Introduction of water molecules into silica glasses was performed by hydrothermal treatment in purified water using an autoclave. The SHG intensity from the electrically poled glasses also increased with the increasing content of water molecules. In this case, the SHG was emitted from the entire region of the sample plate. The origin of the nonlinearity is tentatively assumed to be due to a frozen electric field created by charge separation with protonic conduction.

Semiconductor device, and manufacturing method thereof

Abstract: An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Amorphous oxide and field effect transistor

Abstract: A novel amorphous oxide applicable, for example, to an active layer of a TFT is provided. The amorphous oxide comprises microcrystals.

Semiconductor device and display device

Abstract: An object of the present invention is to decrease the resistance of a power supply line, to suppress a voltage drop in the power supply line, and to prevent defective display. A connection terminal portion includes a plurality of connection terminals. The plurality of connection terminals is provided with a plurality of connection pads which is part of the connection terminal. The plurality of connection pads includes a first connection pad and a second connection pad having a line width different from that of the first connection pad. Pitches between the plurality of connection pads are equal to each other.

Low-temperature fabrication of high-performance metal oxide thin-film electronics via combustion processing

Abstract: Solution-deposited metal oxides show great potential for large-area electronics, but they generally require high annealing temperatures, which are incompatible with flexible polymeric substrates. Combustion processing is now reported as a new low-temperature route for the deposition of diverse metal oxide films, and high-performance transistors are demonstrated using this method.

Semiconductor device, electronic device, and method of manufacturing semiconductor device

Abstract: To provide a semiconductor device and a display device which can be manufactured through a simplified process and the manufacturing technique. Another object is to provide a technique by which a pattern of wirings or the like which is partially constitutes a semiconductor device or a display device can be formed with a desired shape with controllability.