Kazutake Taniguchi

Localized Removal of a Photoresist by Atmospheric Pressure Micro-plasma Jet Using RF Corona Discharge

Atmospheric pressure micro-plasma jet (µ-PJ) was generated at the tip of a stainless steel surgical needle with an inner diameter of 0.4–0.5 mm and with a length of 19–25 mm using RF (13.56 MHz) corona discharge. The He µ-PJ spouted to a free space at a power of less than 10 W. The He atomic excitation temperature (Texc) estimated by means of an optical emission spectrum was 3270 K at a gas flow rate of 350 sccm and Texc decreased with increasing gas flow rate. The O2 µ-PJ was also generated at a power of 12 W and it was applied to the localized removal of a photoresist.

Magnetic shape memory effect in orbital-spin-coupled system MnV2O4

Magnetic-field(H)-induced shape memory effect without temperature variation is demonstrated by a combination of H-sweep and H-rotation in an orbital-spin-coupled spinel-type insulating system MnV2O4. A rotation of the direction of a magnetic field of 5 T in the low-temperature tetragonal phase gives rise to a large macroscopic strain up to 1%, which stems from a 90° rotation of tetragonal domains. The results show several possible ways of macroscopic shape control in this class of matter, and may open a possibility of high-speed actuators free from the eddy current.

Generation of Integrated Atmospheric-Pressure Microplasmas

This work is based on the motivation that by integrating microplasmas confined in a small volume, a large area high-density plasma source could be developed. Firstly, He gas microplasmas were generated by capacitively coupled plasma (CCP) and inductively coupled type plasma (ICP-type) in single small diameter ceramic tubes supplied with 13.56 MHz power via electrodes. Then, based upon the obtained characteristics, sustaining voltage and RF power variations were discussed for integrating tubes two and three dimensionally. However, the presence of the CCP component was noticed from the weak discharge around the center of the highly integrated ICP-type. Therefore, the generation of planar-type plasma was also studied using narrow comb electrodes, which enabled us to produce the discharge at a lower voltage in accordance with Paschens law. As a result, uniform plasma was successfully generated in an area of 12 mm×12 mm. Atmospheric-pressure microplasma generation of pure N2 gas as well as He gas was realized by planar type plasma at low sustaining voltages.

Magnetic-field effects on Jahn-Teller distortion in ferroelastic magnetic insulator Fe1−xMnxCr2O4

The magnetic field response of Jahn-Teller distortion associated with the e orbital was investigated by x-ray diffraction in Fe1−xMnxCr2O4 for x = 0 and 0.7. Successive structural domain rearrangements occurred when a magnetic field was applied along the [001]c axis in the orthorhombic phase of FeCr2O4. The domain rearrangements caused significant magnetostriction, which was observed by using a strain gauge. Reversible magnetostriction also appeared just above the structural transition temperature TS1 in Fe0.3Mn0.7Cr2O4, in which TS1 meets the ferrimagnetic transition temperature TN1 by Fe substitution.

Fluorescence modulation of long DNA molecules adsorbed onto a microelectrode surface

Using microfabricated electrodes, we demonstrate fluorescence modulation of deoxyribonucleic acid (DNA) stained with dye through the application of cyclic electric fields. The fluorescence of DNA adsorbed onto an electrode was quenched under the potentials greater than about 1 V, and was recovered by reducing the potentials to below about 0.6 V. The quenching was observed even for a single DNA molecule adsorbed on an electrode. Therefore, the fluorescence modulation of DNA by external electric fields can be expected as one of selective detection methods for adsorbed DNA onto electrodes.

Fluorescence Emission Control of Long DNA Molecules Adsorbed on Microelectrode Surfaces by External Voltage

Using microfabricated electrodes, we demonstrate emission control of long DNA molecules by the application of external electric fields. We discovered that fluorescence quenching of long DNA molecules is induced by applying an electric potential greater than the threshold to the electrodes. The quenching only occurs in DNA molecules adsorbed on an anode electrode. Fluorescence emission is recovered by turning off the potential. In order to investigate this quenching and subsequent re-emission, we performed simultaneous measurements by cyclic voltammetry with fluorescence imaging.

Nanohole and dot patterning processes on quartz substrate by R–θ electron beam lithography and nanoimprinting

Fine hole and dot patterns with bit pitches (bps) of less than 40 nm were fabricated in the circular band area of a quartz substrate by R–θ electron beam lithography (EBL), reactive ion etching (RIE), and nanoimprinting. These patterning processes were studied to obtain minimum pitch sizes of hole and dot patterns without pattern collapse. The patterning on the circular band was aimed to apply these patterning processes to future high-density bit-patterned media (BPM) for hard disk drive (HDD) and permanent memory for the long life archiving of digital data. In hole patterning, a minimum-22-nm-bp and 8.2-nm-diameter pattern (1.3 Tbit/in.2) was obtained on a quartz substrate by optimizing the R–θ EBL and RIE processes. Dot patterns were replicated on another quartz substrate by nanoimprinting using a hole-patterned quartz substrate as a master mold followed by RIE. In dot patterning, a minimum-30-nm-bp and 18.5-nm-diameter pattern (0.7 Tbit/in.2) was obtained by introducing new descum conditions. It was observed that the minimum bp of successful patterning increased as the fabrication process proceeded, i.e., from 20 nm bp in the first EBL process to 30 nm bp in the last quartz dot patterning process. From the measured diameters of the patterns, it was revealed that pattern collapse was apt to occur when the value of average diameter plus 3 sigma of diameter was close to the bp. It was suggested that multiple fabrication processes caused the degradation of pattern quality; therefore, hole patterning is more suitable than dot patterning for future applications owing to the lower quality degradation by its simple fabrication process.