Takeshi Ozawa

Optimizing coverage of metal oxide nanoparticle prepared by pulsed laser deposition on nonenzymatic glucose detection.

Metal oxide nanoparticles prepared by pulsed laser deposition (PLD) were applied to nonenzymatic glucose detection. NiO nanoparticles with size of 3 nm were deposited on glassy carbon (GC) and silicon substrates at room temperature in an oxygen atmosphere. Transmission electron microscope (TEM) image showed nanoparticles with the size of 3 nm uniformly scattered on the Si(001) substrate. Unlike co-sputtering nanoparticle and carbon simultaneously, the PLD method can easily control the surface coverage of nanoparticles on the surface of substrate by deposition time. Cyclic voltammetry was performed on the samples deposited on the GC substrates for electrochemical detection of glucose. The differences between peak currents with and without glucose was used to optimize the coverage of nanoparticles on carbon electrode. The results indicated that optimal coverage of nanoparticles on carbon electrode.

Effects of post exposure bake temperature and exposure time on SU-8 nanopattern obtained by electron beam lithography

SU-8 is a photoresist imaged using UV rays. However, we investigated the characteristics of an SU-8 nanopattern obtained by electron beam lithography (EBL). In particular, we studied the relationship between post-exposure bake (PEB) temperature and exposure time on an SU-8 nanopattern with a focus on phase transition temperature. SU-8 residue was formed by increasing both PEB temperature and exposure time. To prevent the formation of this, Monte Carlo simulation was performed; the results of such simulation showed that decreasing the thickness of SU-8 can reduce the amount of residue from the SU-8 nanopattern. We confirmed that decreasing the thickness of SU-8 can also prevent the formation of residue from the SU-8 nanopattern with EBL.

Property Variation of Ni--W Electroformed Mold for Micro-Press Molding

We proposed a simple method to fabricate a Ni–W electroformed mold for glass micro-press molding. For example, borosilicate glass (D263) was molded using the Ni–W electroformed mold. A Ni–W electroformed mold with a fine line was fabricated by photolithography and electroforming technology. Additionally, the Ni–W electroformed mold did not require a release layer. As the result of molding D263 at 883 K, the minimum pitch of the glass pattern was the same as that of the Ni–W electroformed mold. We argue that the crystallization of amorphous Ni–W occurred with the activation energy derived from the heating of micro-press molding. The heating temperature was 833 K. Additionally, the release characteristics of a Ni–W film were improved by increasing the percentage of W. In terms of the thermochemical stability and high content rate of W, we indicated that Ni–W electroformed molds can be used repeatedly for glass micro-press molding.

Growth of Nanocubic MgO on Silicon Substrate by Pulsed Laser Deposition

Magnesium oxide (MgO) prepared by both pulsed laser deposition and sputtering methods showed constriction of lattice constants. To emphasize the effect of the constriction of lattice constants, MgO prepared at high oxygen atmosphere and high substrate temperature, resulted in the growth of cubic-shaped magnesium oxide (MgO) nanoparticles on a Si substrate. In oxygen atmosphere, the nanocubic MgO was scattered on the substrate without the Si surface being covered by a MgO thin film. Interestingly, the growth of nanocubic MgO was restrained on the samples prepared in nitrogen atmosphere. The formation of nanocubic MgO is related to the deposition pressure as well as the etching effect provided by oxygen atmosphere.

Periodic nano trench structure fabricated by high-speed scanning CW laser

We report periodic nanostructure on solid material irradiated by scanning continuous wave (CW) laser. Long periodic nano strip grating lines (nano-SGL) formed, not in a spot, but along the trace of the beam scan, literally parallel to each other with a at trough between the strip lines. The period of nanostructure was varied with the laser power between 500 nm and 800 nm, which equals to wavelengths used for laser scanning of green and infrared lasers. Thermal simulation and Raman spectra indicated the temperature of target exceeded the melting temperature to form the periodic nanostructure on target materials.

Formation of highly planarized Ni–W electrodeposits for glass imprinting mold

We confirmed that increasing the total metal concentration is effective for the planarization of Ni–W films and Ni–W nanopatterns formed with a uniform height and a 480 nm pitch. At the same time, the W content in Ni–W films decreased. We investigated the relationship between the planarization of Ni–W films and the W content in Ni–W films, and confirmed that increasing the total metal concentration is effective for the inhibition of hydrogen generation. We pointed to the inhibition of hydrogen gas generation as a cause of the planarization of Ni–W films, and the reduction in the hydrogen generation amount necessary for the deposition of W as a cause of the reduction in the W content in Ni–W films. In order to obtain a flat plating film with a high W content, it is necessary to generate an adequate amount of hydrogen on the surface of the cathode and to remove hydrogen gas from the cathode surface immediately.

Effect of metal ion concentration in Ni–W plating solution on surface roughness of Ni–W film

Since nanopatterns are used for various purposes including solar cells, super-hydrophilicity, and biosensors, it is necessary to miniaturize the patterns on glass devices from micro- to nano-order. We have studied glass imprinting as an excellent microfabrication technology for glass devices. Uniformity of the nanopattern height is required for a mold, since a nodular structure on the Ni–W surface is recognized as a problem in Ni–W nanopattern formation. We confirmed that the Ni–W plating bath increasing metal ion concentration is effective for inhibition of the nodular structure on the Ni–W film, and succeeded in Ni–W nano pattern formation with uniform height. However, the W content rate of plated Ni–W film was reduced in exchange for enhancing the flatness of the Ni–W film. It is necessary to examine the Ni–W plating condition for obtaining planarization of the Ni–W surface and a high content rate of W in the Ni–W film.

Effect of post annealing on MgO thin film prepared on silicon(001) substrate in high oxygen pressure and high substrate temperature by pulsed laser deposition

Epitaxial growth of MgO was verified with the relation of MgO(100) parallel to Si(100) (cubic on cubic growth) even with a large mismatch of lattice constants ~ 22%, instead of 9% mismatch in 45° rotation growth. MgO films prepared at higher deposition temperature showed (001) preferred orientation on Si(001) substrate. After post-annealing the MgO thin films, the pole figure of X-ray diffraction verified the epitaxial growth of cubic on cubic relation. Fe3Si thin film was deposited on Si(001) substrate with the MgO film as buffer layer.