Papers by Author: Masumi Saka

Abstract: Electromigration (EM) is the phenomenon of atomic diffusion in a metallic film with a high-density electron flow. Our group used EM to fabricate Al micro-materials. The EM technique can be used to fabricate micro-materials with a high aspect ratio, pure metal components, an arbitrary form, and a single-crystal structure. Recently, two micro-materials have been simultaneously fabricated using an array pattern consisting of parallel or series connections. However, multiple micro-materials have not been fabricated simultaneously thus far. In this study, a new comb sample pattern was used with a conductive passivation film to produce multiple Al micro-materials.

Abstract: The technique for fabricating Al micro-materials using a conductive passivation film by electromigration (EM), which is the physical phenomenon of atomic transport with high-density electron flow, has been reported. Conductive passivation film precludes the unplanned hillock formation and substantially simplifies the sample preparation time for fabricating Al micro-materials by EM. To date, TiN that is electrical conductive material has been used as a passivation film. However, the TiN passivation oxidizes during heat and current test for fabricating Al micro-materials by EM because of inherent poor oxidation resistance of TiN. Oxidation of passivation causes a problem that applying current occasionally becomes difficult. The present paper proposes a new conductive passivation made of CrN for fabricating Al micro-materials by EM. CrN is used as a countermeasure against the oxidation problem. Additionally, the growth of Al micro-materials by EM is investigated in the relation with the experimental conditions of current and substrate temperature. As a result, we report that the fabrication of Al micro-materials using the CrN passivation is successfully demonstrated in the relation with the experimental conditions.

Abstract: Recently, a technique for fast and accurate phase analysis called sampling moiré method has been developed for measurement of small-displacement distribution. In this study, a distribution of phase error caused by linear interpolation in case with mismatch between the sampling pitch and the grating pitch is theoretically analyzed. Moreover, a technique for effective phase compensation is proposed to reduce the periodic phase error. The performance of our compensation method is validated by a computer simulation. Phase analysis can be performed more accurately even in the case that the sampling pitch does not match to the grating pitch strictly.

Abstract: Migration of atoms is presented to be utilized for fabrication of metallic micro/nanomaterials by controlling the phenomenon. Two kinds of migration phenomena are treated; one is electromigration and the other is stress migration. In addition to the formation of micro/nanomaterials, some achievements in enhancing their functions are demonstrated. One is a technique to fabricate nanocoils from the formed Cu nanowires. The others are techniques to weld or cut the micro/nanowires by using Joule heating. Finally, regarding evaluation of mechanical and electrical properties of the micro/nanomaterials, the concentrated-mass cantilever technique in atomic force acoustic microscopy and the four-point atomic force microscope technique are shown to be powerful tools, respectively.

Abstract: Quantitative evaluation of small cracks in stainless steel under water, which simulated the environment of unclear reactor, by using microwave, was demonstrated. The crack depth was evaluated by means of the microwave dual frequency technique, and the crack closure stress was estimated based on the compliance technique.

Abstract: An acoustic resonant spectroscopy technique for measuring the acoustic impedance of micron-scale polymer films without knowing any values of ultrasonic velocity, thickness and density has been developed. The method, which is based on spectral analysis, observes the acoustic resonance between water, the film and a tungsten plate with high acoustic impedance. The acoustic impedances of poly(vinyl chloride), poly(vinyl alcohol) and nylon films are determined by the spectroscopy technique. Moreover, the values of ultrasonic velocity and density of the films are also determined from the resonance frequencies of the films.

Abstract: General thermometers pose difficulty in measuring the actual surface temperature of a micro-area, especially in electronic devices. In the present study, an approach to direct measurement of surface temperature is described, which utilizes the potential of melting point of different chemical reagents. The present technique exhibits a temperature resolution of about 5○C and the measurable maximum temperature of about 200○C. A short comment on the application of the technique to determine the actual surface temperature of small areas in some engineering applications
is also stated.

Abstract: Nondestructive evaluation of tightly closed small cracks in carbon steel has been investigated under no load conditions. The investigation has been carried out by using a new ultrasonic method of testing, which has the capability of dealing with smaller tight cracks sensitively. Tight closure of small fatigue cracks in carbon steel plates is realized when the measured responses are compared with the calculated responses of the identical open cracks. Highly sensitive characteristic of the present method is verified through the comparison of the results with those obtained by the standard ultrasonic method of testing.

Abstract: A direct-current potential-drop NDE technique has been developed for the evaluation of a 3-D back-wall crack in thick-walled structures. The measuring system contains two pairs of probes – one for current supply and the other for the measurement of potential-drop, where the currentsupply and measuring probes are in close proximity to each other. The optimum arrangement of the four-point-probes system is determined from the finite-element simulation of the three-dimensional electric crack problem. The predicted potential-drop across the crack has been verified experimentally using the newly developed measuring sensor. Measured results of semi-elliptical cracks in stainless steel plates establish the practicality as well as reliability of the present potentialdrop method of testing for the evaluation of 3-D back-wall cracks in thick-walled structures.

Abstract: An ultra-precision instrument with concomitant micromanipulation techniques is designed and set up to measure the damage strength of a single biomimetic microcapsule. It can provide the capability of simultaneously measuring the applied force and resultant displacement of a single microcapsule, with maximum force range of 5mN, resolution of 0.1µN and ultimate traveling distance up to 12mm, resolution of 1nm, respectively. By armed high magnification side-view system, it can offer extra and withal valuable information for the supervened analyzing. The bursting force of urea-formaldehyde biomimetic microcapsules of diameter 65µm in glucose solution was measured by this technique. The microcapsule was burst when the deformation reached a value of 56.2% of its diameter and the corresponding resonant force is about 1700µN. The technique provides an effective means to characterize elastic properties of micro biomimetic capsules and compare mechanical strength of microcapsules made of different ingredients.