Yasuroh Iriye

Experimental and theoretical study of an on-wall in-tube flexible thermal sensor

We propose a novel type of on-wall in-tube flexible thermal sensor, which is able to measure the flow rate under both developing and fully developed flow conditions. We fabricated the thermal flow sensor on a flexible polyimide film by using polymer MEMS technologies and formed a ring-shaped on-wall in-tube sensor configuration by inserting the sensor into a tube. The resistance of the sensor linearly changed with the change in temperature. Its temperature coefficient of resistance is 0.0026 K?1. We obtained a constant and stable output signal of the sensor even though the sensor position was near the tube entrance region where the flow is developing a hydraulic flow condition. We concluded that the proposed sensor is able to measure the flow rate under both the developing and the fully developed hydraulic flow conditions.

Experimental and numerical analyses on recovery of polymer deformation after demolding in the hot embossing process

In a hot embossing process, optimization of the demolding temperature is quite important to achieve high throughput because the cooling step before demolding takes a relatively long time in the process cycle. The authors experimentally examined the influence of demolding temperature on polymer deformation. Polymer deformation was also examined using a finite element simulation tool which assumed the polymer as a viscoelastic body represented by the generalized Maxwell model. In both experiments and numerical simulations, demolding at higher temperature resulted in smaller deformation. Numerical simulations revealed that recovery of polymer deformation occurred in the cooling step after demolding at temperatures higher than the glass transition temperature of polymer. In addition, numerical simulation enables detailed analysis of the impacts of various parameters on the recovery phenomena. This numerical simulation method is expected to be a powerful tool for optimization of the hot embossing process cycle.

Time dependent analysis of the resist deformation in thermal nanoimprinta)

Time evolution of the resist deformation process in the thermal nanoimprint lithography (NIL) has been investigated by both experiment and simulation study. For the numerical simulation, the authors newly developed a simulator using generalized Maxwell model as the viscoelastic constitutive model in conventional finite element method, which handles the complete NIL operations including resist pressing, cooling, and demolding processes. The dependency on the linewidth of the filling rate was investigated by both experiments and simulation and they sufficiently agreed with each other. It is confirmed that narrow pattern (high aspect ratio pattern) was difficult to be filled in a short period under the same imprinting pressure.

Numerical simulation on neutral beam generation mechanism by collision of positive and negative chlorine ions with graphite surface

We investigated ion neutralization by collision with graphite by numerical simulation based on time-dependent density functional theory. It is known that the neutral beam source developed by Samukawa (2001 Japan. J. Appl. Phys. Part 2 40 L779), where neutral particles are generated by the collision of ions from plasma with a graphite electrode with numerous high-aspect-ratio apertures, can achieve very high neutralization efficiency of over 90% when negative ions (Cl−) are used compared with about 60% when positive ions are used. To understand the neutralization theoretically, we developed a numerical simulator and calculated the dynamic process of electron transfer between an ion and graphite during the whole collision process. Multiple collisions were considered in the calculation. We found that Cl− had higher neutralization efficiency (more than 90%) than (about 34%), which is in excellent agreement with the experimental result, so our simulator could successfully simulate the neutralization process. The difference in neutralization efficiency between and Cl− may be due to the relationship between the ion and graphite orbital energy levels.

Development of quartz etching database and 3-D micromachining simulation system

We have characterized anisotropic etching properties of single-crystal quartz by using a spherical specimen made of alpha-quartz. Spherical specimen allowed us to measure etching rates for a number of orientations with a single etching operation. Measured etching-rates further allowed us to perform complete 3-D etching simulation for arbitrary oriented quartz wafer.

Numerical study on electron transfer mechanism by collision of ions at graphite surface in highly efficient neutral beam generation

We investigated the neutralization mechanism of ions created by collisions with a graphite surface by numerical simulations using an efficient and stable simulator developed by us based on time-dependent density functional theory (TD-DFT) to clarify the mechanism responsible for generating neutral beams in a highly efficient neutral beam source developed by Samukawa et al (2001 Japan. J. Appl. Phys. 40 L779). The results from the simulations revealed that negative ions (Cl?) have higher neutralization efficiency than positive ions , which was consistent with previous experimental results. The origin of this difference was investigated in terms of the energy alignment between electronic states participating in the charge transfer process. We found that the electronic states of Cl? have similar energies with those of graphite, while those of and graphite have large differences in energies. This could be interpreted as resonant charge transfer occurring in the neutralization process of negative ions, while Auger charge transfer is dominant in that of positive ions. This interpretation was also strengthened by results where electron transfer probability to the excited states was much larger for collisions of graphite with than with Cl?. This suggested that the different mechanisms are the reason for the difference in neutralization efficiency between negative and positive ions.

Quartz tuning-fork type AFM probe operated in Anti-phase Vibration Mode

This paper presents that quartz tuning fork shows excellent properties as atomic force microscopy (AFM) probe. We used focused ion beam (FIB) system to monolithically form a sharp tip at the side end of one beam. The fabricated probe can vibrate and detect the deformation itself because of piezoelectric property of crystal quartz. We evaluated the vibration characteristic and the self-detection ability of tuning fork. The tuning fork probe is actuated in two different vibration mode; in-phase and anti-phase mode, and clarified that high Q-factor of 5247 was obtained in anti-phase mode. We further applied this mode for AFM observation and images were successfully with dynamic AFM system

Improved numerical calculation of the generation of a neutral beam by charge transfer between chlorine ions/neutrals and a graphite surface

The charge transfer process between chlorine particles (ions or neutrals) and a graphite surface on collision was investigated by using a highly stable numerical simulator based on time-dependent density functional theory to understand the generation mechanism of a high-efficiency neutral beam developed by Samukawa et al (2001 Japan. J. Appl. Phys. 40 L779). A straightforward calculation was achieved by adopting a large enough unit cell. The dependence of the neutralization efficiency on the incident energy of the particle was investigated, and the trend of the experimental result was reproduced. It was also found that doping the electrons and holes into graphite could change the charge transfer process and neutralization probability. This result suggests that it is possible to develop a neutral beam source that has high neutralization efficiency for both positive and negative ions.

Development of Self-Vibration and -Detection AFM Probe by using Quartz Tuning Fork

We developed a novel type of quartz tuning-fork probe that vibrates and detects its own probe deformation, for application to atomic force microscopy (AFM). This tuning-fork probe improves the AFM image resolution because of its high Q (quality) factor value. The tuning-fork probe has a sharp tip that was fabricated using anisotropic wet etching and a focused ion beam system. We evaluated the vibration properties of the tuning-fork in both the in-phase and anti-phase driving mode, and measured a Q factor value of 2808 in the anti-phase mode. We also confirmed that the tuning-fork probe is able to measure a 100 nm-step on a silicon surface by self-vibration and self-detection, without using external vibration and optical-detection mechanisms.