Magnetic immunoassays utilizing magnetic marker and high T_c superconducting quantum interference device (SQUID) have been performed. In this magnetic method, binding-reaction between an antigen and its antibody is detected by measuring the magnetic field from the magnetic marker. First, we discuss the magnetic property of the marker, and show that Fe₃O₄ particles with diameter of 25 nm can be used for remanence measurement. We also show a design of the SQUID for sensitive detection of the magnetic signal from the marker. Next, we developed a measurement system utilizing the SQUID and a reaction chamber with very low magnetic contamination. Finally, we conducted an experiment on the detection of the biological materials called IL8 and IgE. At present, a few atto-mol of IL8 and IgE has been detected, which shows the high sensitivity of the present method.

Multichannel superconducting quantum interference device (SQUID) systems based on double relaxation oscillation SQUIDs (DROS) were developed for measuring magnetocardiography (MCG) and magnetoencephalography (MEG) signals. Since DROS provides large flux-to-voltage transfer coefficients, about 10 times larger than the DC SQUIDs, direct readout of the SQUID output was possible using compact room-temperature electronics. Using DROSs, we fabricated two types of multichannel systems; a 37-channel magnetometer system with circular sensor distribution for measuring radial components of MEG signals, and two planar gradiometer systems of 40-channel and 62-channel measuring tangential components of MCG or MEG signals. The magnetometer system has external feedback to eliminate magnetic coupling with adjacent channels, and reference vector magnetometers were installed to form software gradiometers. The field noise of the magnetometers is around 3 fT/ at 100 Hz inside a magnetically shielded room. The planar gradiometer systems have integrated first-order gradiometer in thin-film form with a baseline of 40 mm. The magnetic field gradient noise of the planar gradiometers is about 1 fT/cm/ at 100 Hz. The planar gradiometers were arranged to measure field components tangential to the body surface, providing efficient measurement of especially MCG signals with smaller sensor coverage than the conventional normal component measurements.

There is a possibility that individuals ingest contaminants that have been accidentally mixed with food because processed foods have become very common. Therefore a detection method of small contaminants in food and pharmaceuticals is required. High-T_c SQUID detection systems for metallic contaminants in foods and drugs have been developed for safety purposes. We developed two systems; one large system is for meat blocks and the other small system is for powdered drugs or packaged foods. Both systems consist of SQUID magnetometers, a permanent magnet for magnetization and a belt conveyor. All samples were magnetized before measurements and detected by high T_c SQUIDs. As a result, we successfully detected small syringe needles with a length of 2 mm in a meat block and a stainless steel ball as small as 0.3 mm in diameter.

Carbon fiber composites are increasingly used as structural materials because of their unique and advantageous characteristics. Carbon fiber reinforced carbon matrix composite (C/C) has the characteristics of high fatigue resistance, fracture toughness and heat resistance up to 3000 K, and is an important component of refractory tiles and nozzles in space shuttles. Useful nondestructive testing methods for C/C are now required. We have developed a SQUID-NDT system based on a non-magnetic coaxial pulse tube cryocooler (PTC), a HTS-SQUID gradiometer and a field generator with ferrite cores that induces high currents in specimens with low electric conductivity. The cryostat with the PTC is compact, at 50 mm in diameter and 400 mm in height. It weighs a total of 4 kg. The system noise is 80 µ₀/Hz^1/2 corresponding to 1.3 nT/m/Hz^1/2 at 100 Hz. We used the system to investigate the usefulness of the SQUID-NDT in detecting flaws in C/C composites. Hidden cracks in C/C multi-layered specimens were detected up to depth of 15 mm. Hidden cracks in C/C-Al stacked sample was also clearly detected. In addition, we magnetically detected the mechanical breaking process of a C/C specimen under tensile load using the current injection method. For this study, a technique for visualizing current detouring defects was developed for detection of deteriorating areas in the specimen. The deteriorating area, identified from the current map, expands during breaking process and agrees with the results obtained by the microscopic observation of the breaking process. The interrupted current I_int, estimated by summing the detour current, clearly changed depending on the stage of the breaking process, suggesting that I_int may be applicable as good index for distinguishing each stage in the breaking process. It is concluded that a SQUID-NDT is applicable to C/C composites and advanced complex materials with low electric conductivity in addition to metallic materials.

The High T_c SQUID was used in an unshielded environment to make eddy current nondestructive testing measurement on a multi-layer aluminum structure. As a demonstration of their capabilities, subsurface defects in a multilayer aluminum structure have been located and mapped using phase shift with no magnetic shielding around the specimen.

The Time Domain Electromagnetic Method (TDEM) survey is one of the several geophysical exploration methods. In the conventional TDEM survey, an induction coil is used as the magnetometer. However, the measurement depth is limited to about 500 m. Using high T_c SQUIDs, there are expectations of large bandwidth and high sensitivity for the TDEM. We developed the high T_c SQUID TDEM system. We have reduced the system noise by developing a 20 mm20 mm step-edge type direct coupled SQUID and a low noise direct readout flux locked loop (FLL) circuit. We have also improved the slew rate, optimizing the parameter of the FLL circuit. Consequently, the system noise of less than 0.2 pT/Hz^1/2 at 1 kHz was achieved in the earth's magnetic field. The slew rate was 7.3 mT/sec. We conducted field trials and confirmed that the TDEM using high T_c SQUIDs obtains information of deeper region with high precision compared with the TDEM using induction coils.

To enable the use of passive transmission lines (PTLs) for the interconnection of single-flux-quantum (SFQ) circuits, we have implemented a driver and a receiver and have developed a method for designing SFQ circuits with passive interconnections. Basic components and properties of passive interconnections, such as the frequency characteristics of the driver and receiver, the PTL delay, and the crosstalk between PTLs, have been experimentally verified. Our developed components and design method have been applied to actual SFQ circuits, such as a 44 switch having block-to-block passive interconnections and a 22 switch having gate-to-gate passive interconnections. We have also shown the advantages of PTLs over Josephson transmission lines (JTLs). We also discuss the prospects of SFQ circuits having passive interconnections.

We have fabricated a multilayer structure for single flux quantum (SFQ) circuit application using a high-temperature superconductor (HTS). La_0.2-Y_0.9Ba_1.9Cu₃O_x (La-YBCO) base electrode layers were prepared by a dc or rf magnetron sputtering method. The reproducibility of film quality for dc-sputtered La-YBCO films was better than that for rf-sputtered films, and the dc sputtered films exhibited the average surface roughness R_a less than 1.0 nm and a T_c zero value of 88 K. By using the dc-sputtered La-YBCO films, a multilayer structure of SrSnO₃/La-YBCO/SrSnO₃/La-YBCO on MgO substrate with R_a below 2.0 nm was obtained. Interface-modified ramp-edge junctions with La_0.2-Yb_0.9Ba_1.9Cu₃O_x (La-YbBCO) counter electrodes have been fabricated by using this multilayer structure with dc-sputtered films. The fabricated junctions exhibited RSJ-type I-V characteristics with I_cR_n products of about 3 mV at 4.2 K. We also obtained a 1-σ I_c spread of 8% for a 1000-junction series-array. The sheet inductance values at 4.2 K for the base and counter electrodes on La-YBCO ground planes were 0.8 pH and 0.7 pH per square, respectively. Operation of several types of elementary SFQ circuits has been successfully demonstrated by using this multilayer structure.

A high temperature superconductor (HTS) filter is designed and measured at 1.93 GHz, using microstrip half-wavelength spiral resonators. Resonant and coupling characteristics of miniaturized microstrip spiral resonators are investigated first. Then a 4-pole Chebyshev bandpass filter with a very narrow passband (4.1 MHz) is designed and realized using microstrip spiral resonators. The filter is fabricated using HTS YBCO films deposited on a LaAlO₃ substrate. The measured frequency response of the filter agrees reasonably with the specifications, and shows that the filter owns excellent property of spurious resonance rejection over a wide frequency range.

2 GHz band electrically tunable superconducting microstrip line band-pass filter was developed. The tunable filter used a thin interdigital electrode. The dielectric distribution of SrTiO₃ substrate included a calculated nonlinear effect of the electrode and ferroelectric material. As a result, the tunable microstrip line filter design with interdigital electrode enabled calculation by the finite element method and the moment method. The tunable filter with a measured unloaded Q factor of 9700 and a frequency shift of 1.25 MHz was obtained.

We briefly survey recent developments in the thin film synthesis and junction fabrication of MgB₂ toward superconducting electronics. The most serious problem in the thin film synthesis of MgB₂ is the high vapor pressure required for phase stability. This problem makes in-situ film growth difficult. However, there has been substantial progress in thin film technology for MgB₂ in the past three years. The low-temperature thin-film process in a UHV chamber can produce high-quality MgB₂ films with T_c 35 K. Furthermore, technology to produce single-crystal epitaxial MgB₂ films has recently been developed by using hybrid physical-chemical vapor deposition. With regard to Josephson junctions, various types of junctions have been fabricated, all of which indicate that MgB₂ has potential for superconducting devices that operate at 20-30 K, the temperature reached by current commercial cryocoolers.

Efficient extraction of interconnect parasitic parameters has become very important for present deep submicron designs. In this paper, the improved boundary element method (BEM) is presented for 3-D interconnect resistance extraction. The BEM is accelerated by the recently proposed quasi-multiple medium (QMM) technology, which quasi-cuts the calculated region to enlarge the sparsity of the overall coefficient matrix to solve. An un-average quasi-cutting scheme for QMM, advanced nonuniform element partition and technique of employing the linear element for some special surfaces are proposed. These improvements considerably condense the computational resource of the QMM-based BEM without loss of accuracy. Experiments on actual layout cases show that the presented method is several hundred to several thousand times faster than the well-known commercial software Raphael, while preserving the high accuracy.

The role of hydrogen in the Si film during excimer laser annealing (ELA) has been successfully studied by using a novel sample structure, which is stacked by a-Si film and SiN film. Hydrogen contents in the Si films during ELA are changed by preparing samples with hydrogen content of 2.3-8.2 at.% in the SiN films with a use of catalytic (Cat)-CVD method. For the low concentration of hydrogens in the Si film, the grain size increases by decreasing hydrogen concentration in the Si film, and the internal stress of the film decreases as increasing the shot number. For the high concentration of hydrogens in the Si film, hydrogen burst was observed at 500 mJ/cm² and the dependence of the internal stress on the shot number becomes weak even at 318 mJ/cm². These phenomena can be understood basically using the secondary grain growth mechanism, which we have proposed.

A systematic experimental and modeling study is reported, which characterizes the low-frequency noise spectrum of 100 nm-MOSFETs accurately. Two kinds of measured spectra are observed: 1/f and non-1/f spectra. The non-1/f spectrum is analysed by forward and backward measurements with exchanged source and drain, and shown to be due to a randomly distributed inhomogeneity of the trap density along the channel and within the gate oxide. By averaging the spectra of identical MOSFETs on a wafer the measured non-1/f noise spectra reduce to a 1/f characteristics. On the basis of these measurement data a noise model for circuit simulation is developed, which reproduces the low-frequency noise spectrum with a single model parameter for all gate lengths and under any bias conditions.

This paper describes two circuit techniques useful for the design of high density and high speed low cost double data rate memories. One is a highly flexible row and column redundancy circuit which allows the division of flexible row redundancy unit into multiple column redundancy unit for higher flexibility, with a new test mode circuit which enables the use of the finer pitch laser fuse. Another is a compact read data path which allows the smooth data flow without wait time in the high frequency operation with less area penalty. These circuit techniques achieved the compact chip size with the cell efficiency of 60.6% and the high bandwidth of 400 MHz operation with CL=2.5.

In this paper, we describe an accelerative current-programming method for active matrix OLED (AM-OLED) display. This new method uses common source configuration, "Acceleration Control" line and some mechanisms to prevent the programming current from flowing through OLED device. It would solve the basic problem of the current-programming pixel circuit: a long programming period, especially at the dark gray-level. The proposed method accelerates the current programming process at any gray levels, and it would be the solution for the problem.

Power distribution in multilayered periodic waveguides is first analyzed by longitudinal modal transmission-line theory (L-MTLT). Novel effective characteristic impedances of the equivalent network for TE and TM modes are then derived, and a symmetrical grating guide with three layers is rigorously evaluated to clarify the validity of our approach. Excellent agreement between our results and the results due to other methods indicates that our approach is able to not only reveal all the physical meaning embedded in the multilayered and multi-sectional periodic waveguides, but also predict various possible Bragg regimes rigorously and simply.

Existence of a surface wave along the boundary between the semi-infinite materials, one of which is a free-space and the other is a material with either negative permeability or negative permittivity, is theoretically investigated. Surface waves exist in only limited combination of negative and positive signs of the material parameters. In addition, by analyzing the surface wave in a finite-thickness slab with negative permeability, its mode profile has been obtained for two different types of symmetry. From these results, the present paper predicts the possibility of a surface wave directional coupler based on a single slab transmission along its top and bottom surfaces.

Non-equal length, three section coupled transmission line couplers are proposed. The proposed structure offers increased design flexibility and the compact circuit design capability over the conventional quarterwave coupled lines. The detailed analysis results and design method are presented along with the numerical and the experimental verification.