This paper reports the development of a novel device with an ultra-thin gap filled with nanofluid in between two parallel metallic electrodes, which will allow, for the first time, practical applicable, affordable, and mass-producible direct thermoelectric energy generation at room temperature. Compared to the state of the art, the power density of our device exceeds conventional thermionic energy generators by orders of magnitude and may offer close to uW power in a volume of 1cm 3 thus making it attractive for IoT, wearable electronics and other standalone applications. In addition, our device is compatible with roll-to-roll and flexible glass processes for low-cost and large area production.

In this work, a resin, which consist of nanoparticles with the diameter from a few nm to tens of nm dispersed in an inert matrix material, was deposited between two parallel metal electrodes with different work functions. This creates a structure capable of direct electrification from low grade heat. Compared to previous devices based on a liquid matrix, a full solid structure of the proposed device enables better device performance, easier device stacking, and inexpensive production by avoiding costly device sealing, thus it is attractive for IoT, wearable electronics and other standalone applications. This paper will show device design, fabrication processes, and evaluation results as well as comparisons to previous devices using liquid matrix materials for further investigation on the underlying physics.

周囲温度の変化による光走査型センサの走査位置検知精度の低下防止と, センサの極限までの小型化を目的として, 小型2次元光走査機構の板ばね部に生じる応力を利用して走査位置を検知する方法を提案し, そのためのピエゾ抵抗素子と反射光検知用のフォトダイオードを2自由度板ばね振動子上にシリコンマイクロマシニングによって一体形成した機能集積化マイクロスキャナを試作し, 基本的な特性について実験により検証した.その結果, 以下のことが明らかとなった.(1) 振動子板ばね上に一体形成したひとつのピエゾ抵抗素子により, 板ばね表面に発生する曲げとねじりの応力を同時に検出し, 直角2方向の光走査位置を検知する方法を試みた.この方法により位置検知精度の低下は, ±10℃の環境温度変化に対して1%以下となり, 前報で報告した板ばねの共振駆動周波数を利用する方法に比べて, 50倍改善することができた.(2) 板ばねにピエゾ抵抗素子を一体形成することにより, 曲げ方向26mV/°, ねじり方向21mV/°, の走査位置検知感度と, 0.02°の走査位置検知分解能が得られた.(3) 試作した外形7mm×7mmのマイクロスキャナは, 最大検出距離200mmまでの物体からの反射光検知, 直角2方向への光走査, および走査位置検知が同時に可能であり, 本スキャナを用いることにより光走査型センサが大幅に小型化できる.

An actuator for micromachined relays has been investigated. The actuator is fabricated by the sealed-cavity process, a micromachining technology. It has a thin Si clamped-clamped beam which is deformed by buckling due to thermal SiO/sub 2/ built-in stress and thermal stress. The actuator size is 2.5 mm(L)/spl times/0.5 mm(W)/spl times/0.02 mm(T). 25-micron deflection at the center point and 2.0 gf force were obtained with 27 V/25 mA input power.

We have developed a diaphragm piezoelectric microactuator. The diaphragm consists of a Pb(Zr, Ti)O3 (PZT) thin film, electrode layers, an isolation layer and a Si substrate. The diaphragm is deflected by transverse stress in the PZT thin film which is fabricated by a sputtering and annealing process. The PZT thin film has a piezoelectric coefficient d 31 of -100 pC/N, which is comparable to that of bulk PZT. A diaphragm deflection of 3 µ m was obtained at an electric field of 16 V/µm.

We describe the improvement of a miniature two-dimensional optical scanner for wide-area optical scanning and low-voltage driving. First, the bending and torsional fracture stresses of a fine leaf spring made of single-crystal silicon were experimentally determined. They were 1 GPa for bending fracture and 0.3 GPa for torsional fracture, and a fatigue fracture tendency was also observed. Based on the determined fracture stresses, an improved two-dimensional fine leaf spring resonator, wherein the wing part of the previous resonator was removed to reduce air resistance, was developed. Also, an additional mass was put on the mirror to create torsioal and bending moments. Secondly, the shape of a moonie actuator, which magnifies the transverse strain of a piezoactuator more than 10 times, was optimized by FEM analysis to produce a large displacement with a low-voltage drive. Consequently, a miniature two-dimensional optical scanner 5mm×10mm×2.2mm in size was developed, which can scan from forty degrees to eighty degrees with a 15-volt drive.

Mn-Zn (Manganese-Zinc) ferrite polycrystals have been widely used as a core material of magnetic heads in video cassette recorders or floppy disk drives of personal computers. In this research, slot grinding was performed to investigate the chipping generation mechanism at slot edge of Mn-Zn ferrite polycrystal with metal bonded diamond wheels. A high precision slicing machine with an air spindle of low friction and low thermal expansion was used. After grinding, the chippings at a slot edge was measured by means of a form tracer with a knife edge tip, and analyzed with a newly developed measurement method using a personal computer under various grinding conditions. On the other hand, by means of SEM observation, a material removal mechanism at the edge of Mn-Zn ferrite was investigated. The results are follows. Pre-process, such as lapping, before grinding can reduce chipping size. Most of chipping is generated by transgranular fracture. As chipping size depends on the removal per grain; qw=α·μ2 (Vw/Vs), a decrease in removal qw, chipping size after slot grinding could be reduced.

A novel micro focusing optical device controlled by a piezoelectric thin film micro actuator has been presented. This device is provided by bonding two micromachined substrates, which are a glass substrate integrated with a surface emitting light element and a micro Fresnel lens on each surface, and a silicon substrate with a diaphragm type of piezoelectric thin film actuator on it. The surface of the thin film is used as a movable reflection mirror. Focusing is performed by changing position of the mirror surface along the optical axis. In the case of applying the micro lens with 1.3 mm of diameter and 0.33 of N.A. to this focusing device and the thin film actuator capable of several micron displacement, focal point shifting of over 100 mm is obtained. Applying the device to optical senors such as a barcode reader, miniaturization of the light source and high resolution detecting for wide range could be possible.

GaAs surfaces were passivated with selenium using Se/NH4OH solution. Selenium powder of 99.8% purity was dissolved in NH4OH and the GaAs substrates were immersed in this solution. The extent of passivation was studied by electrical measurements (current-voltage characteristics) of the Schottky diodes. The experimental results indicated that the surface properties were substantially improved without requiring a succeeding Na2S treatment. The degradation of the ideality factor, n, of the Schottky diodes was efficiently retarded by this selenium passivation. The surface chemistry of the passivated GaAs surface was investigated with X-ray photoelectron spectroscopy (XPS). The XPS data indicated that both the oxidation of the GaAs surface (formation of Ga2O3 and As2O3) and segregation of elemental arsenic ( As0) at the surface were suppressed or retarded by this passivation. This corresponds well to retardation of degradation of the n value. As2Se3 was observed in the Se/NH4OH-passivated surface, which suggests that the segregated As was removed by chemical reaction between As and Se to produce As2Se3. There is a possibility of the formation of Ga2Se3 (Ga-Se bond), though it is not observed in our XPS data. The formation of As-Se and/or Ga-Se bonds is suggested as the reason for suppression of oxidation of the GaAs surface. When the Se-passivated surface was exposed to air ambient, the total amount of selenium and the amount of As2Se3 decreased. This may be due to oxidation of As2Se3 to form As2O3. The extent of Se/NH4OH passivation and the degree of degradation due to air exposure are similar with those of the ( Na2Se/NH4OH+Na2S) passivation reported by Sandroff et al. [J. Appl. Phys. 67 (1990) 586].

Piezoelectric thin films are very promising materials for MEMS applications because they have application flexibility and compatibility with semiconductor and micromachining processes. How to design MEMS devices with piezoelectric thin films, the mechanical characteristics, and how those characteristics can be controlled by process conditions is discussed in this paper. In addition, piezoelectric/electric characteristics must be understood. With this background, mechanical characteristics (Young's modulus and built-in stress) measurements of sputtered Pb(Zrx, Ti1 - x) O3 thin film, one of piezoelectric materials, have been carried out using the load-deflection method. Relationships between post anneal conditions and those characteristics are discussed. It was shown from the experiment results that Young's modulus increases as anneal temperature/time increases. The maximum value was 76.6 GPa(700 degrees C/3600 sec) which is more than three times larger than that of as-depo film. Built-in stress is also affected by post anneal process and ranges from 0.04 GPa(as-depo) to 0.41 GPa(700 degrees C/60 sec). SEM observation results made it clear that it was caused by film shrinkage due to grain enlargement during anneal process.

Effects of post-thermal annealing on the various sulfur passivations of GaAs were investigated using X-ray photoelectron spectroscopy (XPS) and electrical measurements of the Schottky diode. The P2S5/NH4OH, ( NH4)2S x and Na2S solutions were used as sulfur sources. The XPS data showed that thermal annealing after any of the passivations studied here, substantially decreased the amounts of both elemental arsenic ( As0) and unstable As-S bonds (probably incomplete compounds such as AsS). On the other hand, the amount of stable Ga-S bonds increased after post-thermal annealing for all the sulfur passivations studied here. These findings show that unstable As-S bonds were converted to stable Ga-S bonds during post-thermal annealing. This behavior was the most marked in the Na2S passivation. Elemental arsenic, As suboxides such as AsO and incomplete As-S bonds are considered to be detrimental to the formation of stable GaAs surface, whereas the full-oxides of both As and Ga ( As2O3 and Ga2O3) and probably the full-sulfide ( As2S3) are not so detrimental. The electrical characteristics were also observed to be considerably improved by the post-thermal annealing. Degradations of electrical characteristics were smallest for the sample annealed after P2S5/NH4OH passivation (and cleaning in deionized water). The P2S5/NH4OH treatment leads to the most robust surface passivation of GaAs among those studied here.

Sulfur passivations of the GaAs surface using P2S5/(NH4)2S x and P2S5/NH4OH solutions were investigated by electrical measurements of the Schottky diodes and by X-ray photoelectron spectroscopy (XPS). The GaAs samples lightly washed in deionized water after both P2S5 passivations showed the lowest degree of degradations in the ideality factor n and the Schottky barrier height φ B due to exposure to air ambient. XPS data indicated that oxidation of As was drastically suppressed by P2S5 passivation with and without washing in deionized water, while oxidation of Ga was not efficiently suppressed by these passivations without washing. This is probably due to the preferential formation of As–S bonds over Ga–S bonds. However, oxidation of Ga was found to be greatly suppressed in the water-washed samples after the P2S5 passivations. A fair amount of As–S bonds ( As x S y , probably AsS and As2S3) was observed in the P2S5-passivated samples without washing, which increased as these samples were exposed to air. This indicates that As atoms diffuse through the rather thick sulfur film and react with S to create As–S bonds during exposure to air. The increase in the amount of unstable As–S bonds is considered to be a cause of the deteriorations in the electrical haracteristics. The amount of As–S bonds was observed to drastically decrease after lightly washing the P2S5-passivated samples in deionized water, whereas the amount of stable Ga–S bonds did not substantially decrease. This is a possible reason for the more stable passivation effect with washing. From the experimental results obtained in this study, it was concluded that the Ga–S bonds are useful and a large amount of the As–S bonds is probably detrimental to stable passivation, though a certain amount of the As–S bonds is necessary to effectively suppress oxidation of As. It is very important to control the amount of sulfur on the GaAs surface to obtain stable passivation.

X-ray photoelectron spectroscopic (XPS) analysis was performed for the Na2S-passivated GaAs surface. The XPS data indicated that oxidation of GaAs was not suppressed by Na2S Passivation, and fair amounts of AS2O3 and Ga2O3 were observed after exposure to air for 3 days in contrast with the case of (NH4)2Sx passivation. However, segregation of elemental arsenic was found to be substantially suppressed by this passivation. Both As, S(y) (probably AsS) and As2S3 were observed at the Na2S-Passivated surface. This is due to diffusion of elemental As through the thick Na2S film and its reaction with S to produce As(x)S(y) and AS2S3, and this is probably the mechanism of suppression of As segregation. After an exposure to air, the XPS signal from As(x)S(y) substantially decreased. This is probably due to the reaction of As(x)S(y) --> As2O3 + SO2 up. The XPS measurement for the (NH4)2Sx-passivated GaAs samples indicated that oxidation was strongly suppressed, but segregation of elemental As was not effectively suppressed by this passivation, consistent with the previous data. As-S bonds were found to disappear upon annealing after (NH4)2Sx passivation. Elemental sulfur was observed after the exposure to air for 3 days for the (NH4)2Sx-passivated samples. This may be due to breakdown of both As-S and Ga-S bonds accompanying oxidation of As and Ga. Schottky diodes were fabricated on the substrates treated in various ways, and I-V characteristics were measured. From the point of view of degradation due to air exposure, the best result was obtained for the (NH4)2Sx-passivated sample with annealing.

X-ray photoelectron spectroscopic (XPS) analysis was performed for the Na2S-passivated GaAs surface. The XPS data indicated that oxidation of GaAs was not suppressed by Na2S passivation, and fair amounts of As2O3 and Ga2O3 were observed after exposure to air for 3 days in contrast with the case of (NH4)2Sx passivation. However, segregation of elemental arsenic was found to be substantially suppressed by this passivation. Both AsxSy (probably AsS) and As2S3 were observed at the Na2S-passivated surface. This is due to diffusion of elemental As through the thick Na2S film and its reaction with S to produce AsxSy and As2S3, and this is probably the mechanism of suppression of As segregation. After an exposure to air, the XPS signal from AsxSy substantially decreased. This is probably due to the reaction of AsxSy→As2O3+SO2↑. The XPS measurement for the (NH4)2Sx-passivated GaAs samples indicated that oxidation was strongly suppressed, but segregation of elemental As was not effectively suppressed by this passivation, consistent with the previous data. As-S bonds were found to disappear upon annealing after (NH4)2Sx passivation. Elemental sulfur was observed after the exposure to air for 3 days for the (NH4)2Sx-passivated samples. This may be due to breakdown of both As-S and Ga-S bonds accompanying oxidation of As and Ga. Schottky diodes were fabricated on the substrates treated in various ways, and I-V characteristics were measured. From the point of view of degradation due to air exposure, the best result was obtained for the (NH4)2Sx-passivated sample with annealing.

X-ray photoelectron spectroscopic (XPS) analysis was performed for the Na 2 S-passivated GaAs surface. The XPS data indicated that oxidation of GaAs was not suppressed by Na 2 S passivation, and fair amounts of As 2 O 3 and Ga 2 O 3 were observed after exposure to air for 3 days in contrast with the case of (NH 4 ) 2 S x passivation. However, segregation of elemental arsenic was found to be substantially suppressed by this passivation. Both As x S y (probably AsS) and As 2 S 3 were observed at the Na 2 S-passivated surface. This is due to diffusion of elemental As through the thick Na 2 S film and its reaction with S to produce As x S y and As 2 S 3 , and this is probably the mechanism of suppression of As segregation. After an exposure to air, the XPS signal from As x S y substantially decreased. This is probably due to the reaction of As x S y →As 2 O 3 +SO 2 ↑. The XPS measurement for the (NH 4 ) 2 S x -passivated GaAs samples indicated that oxidation was strongly suppressed, but segregation of elemental As was not effectively suppressed by this passivation, consistent with the previous data. As-S bonds were found to disappear upon annealing after (NH 4 ) 2 S x passivation. Elemental sulfur was observed after the exposure to air for 3 days for the (NH 4 ) 2 S x -passivated samples. This may be due to breakdown of both As-S and Ga-S bonds accompanying oxidation of As and Ga. Schottky diodes were fabricated on the substrates treated in various ways, and I-V characteristics were measured. From the point of view of degradation due to air exposure, the best result was obtained for the (NH 4 ) 2 S x -passivated sample with annealing.