An ultra-small tactile sensor with functions of signal processing and digital communication has been prototyped based on MEMS-CMOS integration technology. The designed analog-digital mixed signal ASIC allows many tactile sensors to connect each other on a common bus line, which drastically reduces the number of wire. The ASIC capacitively detects the deformation of a force sensor and sends digital data to the common bus line when the force exceeds a threshold. The digital data contain a physical ID of each sensor, 32-bit sensing data and 16-bit cyclic redundancy check (CRC) code. In this study, a novel wafer-level integration and packaging technology were developed, and a chip-size-packaged tactile sensor with a small footprint (2.5mm×2.5mm) and a low profile (0.27mm) was prototyped and tested. The sensor autonomously sends digital data like a tactile receptor of human.

200 eV and 30 keV Si2+ FIB were implanted in an MBE-grown GaAs layer in a dose range of 1012 and 1013 cm-2. Successive overlayer regrowth of the GaAs cap layer and postannealing at 800 °C for 3 – 30 s was performed to form buried thin δ-doped like layers. From the measurement of the sheet carrier density and the mobility, it was observed that doped layers had a carrier density ranging from 5×1011 to 1×1013 cm-2 and mobilities which were almost the same order in magnitude as that of an MBE-grown δ-doped sample.

Two types of shape and contrast features of superconducting vortices in a Lorentz micrograph were obtained by the newly developed 1-MV field-emission transmission electron microscope on a Bi2Sr2CaCu2O8+8(Bi-2212) thin specimen containing tilted columnar defects. The shape and contrast features could be consistently interpreted by the simulation that some vortices were pinned along tilted columnar defects and others were unpinned. The interesting property for temperature change of vortex core inside the material was also observed.

A single crystalline Bi2Sr2CaCu2O8+8 which has columnar defects in its inside are observed by Lorentz microscopy using the newly developed 1-MV field emission electron microscope at the first time. The superconducting vortices are observed with higher contrast than ever. Simultaneous observation of vortices and columnar defect is succeeded in real time.

We have developed a well-controlled method for manipulating carbon nanotubes. The first crucial process involved is to prepare a nanotube array, named nanotube cartridge. We have found the ac electrophoresis of nanotubes by which nanotubes are aligned at the knife-edge. The nanotubes used were multiwalled and prepared by an arc discharge with a relatively high gas temperature. The second important process is to transfer a nanotube from the nanotube cartridge onto a substrate in a scanning electron microscope. Using this method, we have developed nanotube tips and nanotube tweezers that operate in a scanning probe microscope. The nanotube probes have been applied for observation of biological samples and industrial samples to clarify their advantages. The nanotube tweezers have demonstrated their motion in scanning-electron-microscope and operated to carry nanomaterials in a scanning probe microscope.

This paper has made an overview on elastic and structural aspects of three distinct superlattices under hydrostatic pressure up to about 8GPa, which were studied by our unique x-ray diffraction technique incorporated with a diamond-anvil cell. They are metallic fcc/fcc Au/Ni, bcc/fcc Mo/Ni, and semiconductive epitaxially-grown PbSe/SnSe superlattices. In their layer-stacking direction, both metallic superlattices show the supermodulus behavior while the semiconductive one doesn't. However, its pressure-driven cubic-to-orthorhombic phase transition, successively taking place in the SnSe and PbSe layers, has been found to significantly shift by stress due to its epitaxial growth.

New types of multilayered photoreceptors using photosensitive a-SiC:H and a-Si:H have been investigated. The a-Si1-xCx:H was deposited at high rate of 1–6 µm/h from SiH4-C2H2 by a plasma CVD and used as a carrier generation layer (CGL) or a carrier transport layer (CTL). The type with the a-SiC:H(x=0.1) as CGL for positive charging shows higher sensitivity at λ<700 nm than the a-Si:H photoreceptors, reflecting the higher photosensitivity and wider band gap of the a-SiC:H. Furthermore, the negative charging type using the a-SiC:H(x=0.1) as CTL shows excellent sensitivity over full visible rangq compared with other positive charging types, because the transport ability of electron is superior to that of hole in both a-Si:H and a-SiC:H.

Highly photosensitive a-SiC:H films exhibiting ημτ-product more than 10−6 cm2/V at the band gap of 1.9 eV are prepared under the high deposition rate around 6μm/h by a plasma decomposition of SiH4-C2H2 source mixture gas at higher rf power. It is also shown that the SiH4-C2H2 gas system has a feature of the carbon incorporation into the films with the content nearly equal to that in the source mixture gas and hence is suitable for the high rate deposition process. This advantage and in addition the requirement of the higher rf power for obtaining the films with good electrical performance are discussed in terms of the dissociation reaction of the source gas and the secondary gas phase reactions in the plasma.

The on/off ratio of the vertical-type metal-base organic transistors was drastically improved by heat treatment in air. The heat treatment after deposition of the collector layer and base electrode reduced the leakage current between the base and collector, resulting in remarkable suppression of the off current. As a result, in addition to the advantage of low voltage and high current operation based on the vertical structure, very high on/off ratio exceeding 105 was achieved.

The effect of carbon incorporation into a-Si:H has been investigated in terms of gap states. The shallow and deep states are measured by a combination of two methods of the time-of-flight and the depletion discharge transient spectroscopy. The results show that the carbon incorporation of 10Z into a-Si:H leads to a slight increase in the conduction-band tail states and an extention of the deep states distribution. However, the increase in the shallow states affects little change in the electron transport properties. The origin of the deep states is also discussed.

New multilayered photoreceptor consisting of all layers of a-Si1−xCx:H (x=0.1−0.8) has been developed on the basis of a high rate deposition process established using a glow discharge in a mixture of SiH4 and C2H2. This SiC photoreceptor is for negative charging and shows the excellent spectral sensitivity that is high in a short wavelength region and is reduced at the wavelengths longer than 600nm, suitable for the plain paper copier. The charge acceptance more than 40V/μn is achieved for the thickness less than 20μm. The charging characteristics are discussed in terms of deep emission states in the a-SiC:H.

Electrical properties of heavily Be-doped GaAs grown by molecular beam epitaxy were investigated systematically in a wide range of Be-concentration from 1× 1014 up to 2× 1020 cm-3 by using yan der Pauw technique. Probable carrier scattering mechanisms observed in this work are discussed by taking into account the radiative mechanisms of several new photoluminescence emissions previously observed in the band-edge-emission region of the samples. All samples were checked their electrical properties first at room-temperature. Five selected samples out of them were measured from 10° K up to room-temperature. Samples having the carrier concentration from 1014 to 1018 cm3 presented typical semiconductor-like conduction with finite carrier excitation energy. For samples having carrier concentration 7× 1016 cm -3, the conduction mechanism at high temperature region above 30β K was dominated by holes thermally excited into valence band. At low temperature region below 30° K . it was dominated by holes hopping from neutral to ionized acceptors with the assistance of phonons. Hole mobilities of samples having the carrier concentration from 1017 to 1018 cm-3 showed an anomalous behavior in the low temperature region, which suggests the presence of a new type of carrier scattering mechanism. A radiative center denoted by lg-gl observed in this concentration region will be a candidate scattering center to explain these electrical behaviors. Samples having the carrier concentration larger than 1019 cm-3 demonstrated typically metallic electric conduction not owing to thermally excited carriers, which means that an impurity band is formed but merged with valence band. The density of state of this combined valence band mixed with impurity band can be supposed to reflect carrier concentration dependence of the PL emission bands observed in this region, i.e. [g-g]α , [g-g]β and [g-g]γ .

Activated carbon fibers are a kind of microporous carbon. Using dangling bond spins attached to the peripheries of the micropores, we investigated the microporous structures in relation to the heat-treatment and gas adsorption effects. Functional groups weakly bonded to the graphitic backbone are removed by the heat-treatment at moderate temperatures 200-400°C, resulting in the generation of a variety of dangling bond spins. The heattreatment above 500°C brings about homogenization of the dangling bond spins. For gas adsorption, the introduction of helium gas strongly enhances the spin-lattice relaxation rate for the dangling bond spins. In addition to a remarkably large condensation of helium gas in the microporous region, the enhancement proves the presence of ultra-micropores which can accommodate only the smallest diameter helium atoms.

A new A4-size contact-type image sensor with 8 elements per millimeter (1,728 elements) was developed by using amorphous silicon alloy pin photodiodes as the light receiving elements. The matrix switching method is employed for signal reading. This method can read the signals from all of the 1,728 photodiodes using a 54 (54-channel input) x 32 (32.channel output) matrix switching scheme. It is advantageous in that the required input and output external circuits can be simplified. To prevent signal crosstalk between the diodes in the matrix, amorphous silicon alloy pin diodes, which are made in the same process as the photodiodes for maintaining a low cost, are connected in series to each photodiode in reverse polarity as blocking diodes.

To achieve superior signal-to-noise ratio and response at the same time, amorphous silicon alloy pin diodes are optimized to satisfy both a high photo-to-dark ratio and a high rectification ratio. The image sensor can operate at up to 2 MHz signal reading clock, maintaining a signal-to-noise ratio of over 24 dB under 0. 1–1x sec exposure.

0.1 and 30 keV Si2+ focused ion beams (FIB) were implanted in two types of GaAs, one of which is semi-insulating (s.i.) GaAs, while the other is grown by molecular beam epitaxy (MBE). Successive regrowth over the implanted surface was performed using MBE-FIB combined system, and the resistance was measured. It was found that for 100 eV Si2+ FIB implantation, the sample was nonconductive without a post annealing at 800°C. After the post annealing, however, the sample became conductive, and the resistance was the same order in magnitude as the sample fabricated using 30 keV Si + FIB irradiation. This suggests a potential of selective formation of Si δ-like doped layers in GaAs and GaAs/AlGaAs using a low-energy FIB.

New DC bias method for the electron cyclotron resonance (ECR) plasma chemical vapor deposition (CVD) is demonstrated, where the highly photosensitive a-Si:H film of the device grade is deposited on the dielectric substrate. The measurement of plasma parameters using a probe technique indicates that the impinging of ion H+ on the growing surface is the key to the high quality a-Si:H film and this DC bias method controls the film properties by the ion density rather than the ion energy.

The heating-rate dependence of crystallization temperature, Tc, and the glass transition temperature, Tg, is studied from the view points of nucleation and fragmentation processes in disordered structures. Tc and Tg are expected to increase monotonically with heating rate. Such behaviors of Tc and Tg are classified into four characteristic regions with respect to the heating rate. Results are summarized in the Transient Phase Diagram where Tc and Tg are given as a function of heating rate. The scaling rule in the Transient Phase Diagram is given.