Metal-induced negative oxide charge detected by an alternating current surface photovoltage in thermally oxidized Fe-contaminated n-type Si (001) wafers

The atomic-bridging type negative oxide charge in SiO₂ is investigated using the Fe-contaminated (001) surface of n-type Si wafers. The investigation is done on the basis of a chemical analysis and a method in which the frequency-dependent alternating current (AC) surface photovoltage (SPV) is measured. At room temperature, an AC SPV appears and gradually increases, saturating after approximately one day (with an Fe concentration on the Si surface of 4.0 × 10¹³ atoms/cm²). The AC SPV eventually becomes inversely proportional to frequency except at very low frequencies (< 10 Hz) corresponding to weak or strong inversion, indicating that the negative Fe induced oxide charge appears in the form of a (FeOSi)⁻ network. Also, in Fe-contaminated n-type Si(001) surfaces thermally oxidized at between 550 and 650 °C for 60 min, strong inversion is unquestionably observed, proving that the (FeOSi)⁻ network survives and that most of the added Fe has segregated into the region closest to the surface of the thin SiO₂ film. At 850 °C and/or for long oxidation times, the AC SPV decreases and ultimately disappears, implying that the (FeOSi)⁻ network has collapsed and may have changed into Fe₂O₃. A model for the metal-induced negative oxide charge in the conventional oxide charge diagram is proposed.     

Contrast enhancement in the phase plate transmission electron microscopy using an objective lens with a long focal length

A new optical condition using an objective lens (OL) of a long focal length (objective mini lens: OM) was tested to enhance image contrast in phase plate transmission electron microscopy (P-TEM). A phase plate was set on the selected area aperture plane where diffraction patterns were formed under the optical condition using the OM. A phase shift by the phase plate was added to the electron waves to visualize phase objects. The application of the OM to the P-TEM should provide higher phase contrast than that obtained by the OL for the phase objects. One of the reasons for the contrast enhancement is that high-angle scattering electron waves which would give the background intensity were not used for image formation due to the large spherical aberration. Another reason is that the cut-on frequency above which the phase shift was added by the phase plate could be smaller using the OL with a long focal length. Experimental results and model calculations showed the contrast enhancement of the biological specimens using the OM.     

CMOS retinal prosthesis with on-chip electrode impedance measurement

A retinal prosthesis device with built-in self-test capability is proposed and demonstrated. The measurement of electrode impedance as a self-test is achieved without increasing the chip area by employing analogue multiplexers to allow the electrodes to be used for both stimulation of retinal cells and measurement of impedance. Measurement is performed using a four-terminal method to ensure good accuracy. A prototype stimulus chip with 16/spl times/16 channels is fabricated using standard 0.6 /spl mu/m CMOS technology, and is demonstrated to provide self-test functionality with error of as little as 0.05% in the frequency range of 100 Hz to 100 kHz.     

Nanowrinkled and Nanoporous Polyethylene Membranes Via Entanglement Arrangement Control

Crystalline homopolymers, including polyethylene (PE), which has the simplest architecture, form a nanometer‐sized combination of crystalline and amorphous components, but their arrangement control, similar to self‐assembled phase‐separation of block‐copolymers, is usually difficult. However, molecular entanglements trapped between crystalline and amorphous components of homopolymers coincide with the segmental linking points on the interfaces of the microphase separation for block copolymers. Nanowrinkled PE membranes are prepared with a network of 30 nm‐thick homogeneous lamellae using a novel entanglement control technique composed of biaxial melt‐drawing and melt‐shrinking procedures, which are limited for highly entangled ultrahigh molecular weight materials. Such a network arrangement of nanowrinkling lamellae spreading on membrane surface and also across the membrane thickness improves the mechanical properties of both tensile strength and tearing strength. Subsequent cold‐drawing causes delamination of the lamellar interfaces, leading to the resultant nanoporous morphology composed of passing‐through channels that are several tens of nanometers in diameter, without any solvent processing.     

Yagi-Uda array for millimetre-wave imaging

An imaging array consisting of five Yagi-Uda antennas in a dielectric has been constructed for 50 GHz that has antenna patterns suitable for millimetre-wave applications. Crosstalk levels of less than -30 dB between adjacent antennas in an f/1.0 imaging array have been measured in 5 GHz model experiments.<>     

Good trellises for IC implementation of Viterbi decoders for linearblock codes

This paper investigates trellis structures of linear block codes for the integrated circuit (IC) implementation of Viterbi decoders capable of achieving high decoding speed while satisfying a constraint on the structural complexity of the trellis in terms of the maximum number of states at any particular depth. Only uniform sectionalizations of the code trellis diagram are considered. An upper-bound on the number of parallel and structurally identical (or isomorphic) subtrellises in a proper trellis for a code without exceeding the maximum state complexity of the minimal trellis of the code is first derived. Parallel structures of trellises with various section lengths for binary BCH and Reed-Muller (RM) codes of lengths 32 and 64 are analyzed. Next, the complexity of the IC implementation of a Viterbi decoder based on an L-section trellis diagram for a code is investigated. A structural property of a Viterbi decoder called add-compare-select (ACS)-connectivity which is related to state connectivity is introduced. This parameter affects the complexity of wire-routing (interconnections within the IC). The effect of five parameters namely: (1) effective computational complexity; (2) complexity of the ACS-circuit; (3) traceback complexity; (4) ACS-connectivity; and (5) branch complexity of a trellis diagram on the very large scale integration (VLSI) complexity of a Viterbi decoder is investigated. It is shown that an IC implementation of a Viterbi decoder based on a nonminimal trellis requires less area and is capable of operation at higher speed than one based on the minimal trellis when the commonly used ACS-array architecture is considered     

A framework for constructing databases for supervisory control systems

This paper presents a framework for constructing databases for supervisory control systems. The proposed framework utilizes a generation-based approach and object-oriented framework libraries. In this framework, a database is designed for the target system from a design template, and the software for the database system is generated from the database design. The generated database system includes a domain-specific object system and a diagram and plant data editor, which provides effective data input functions. © 1998 Scripta Technica, Electr Eng Jpn, 123(1): 32–42, 1998     

Pixel design of pulsed CMOS image sensor for retinal prosthesis with digital photosensitivity control

A newly designed pulse frequency modulation photosensor for use in retinal prosthesis is proposed and demonstrated. The pixel converts the intensity of incident light into biphasic current pulses at frequencies suitable for the electrical stimulation of retinal neurons. Experimental results showed that the device was sensitive over a dynamic range of input light of about 120 dB, and that photosensitivity could be varied from 0 dB to around -40 dB.     

Organic LED full-color passive-matrix display

Abstract— A full-color 5.2-inch 1/4-VGA passive-matrix organic LED display has been developed, adopting selective deposition for the different emitting materials. The display features 320 (×3) × 240 pixels with an equivalent pixel size of 0.33 × 0.33 mm, white peak luminance of over 150 cd/m², and power consumption of 6 W.     

Risk factors for silent cerebral infarcts in subcortical white matter and basal ganglia

BACKGROUND AND PURPOSE: The purpose of this study was to clarify whether the relevant risk factors for silent cerebral infarcts (SCIs) in subcortical white matter (WM) are different from those in the basal ganglia (BG). METHODS: Subjects of this study were 219 adults without a history of stroke or transient ischemic attack and without any abnormality on a neurological examination who consecutively visited the neurology service in our hospital between January 1994 and November 1997 requesting medical evaluation for possible cerebrovascular diseases. Subjects included 141 men and 78 women ranging in age from 33 to 83 years (mean+/-SD, 63.2+/-9.5 years). We performed brain MRIs and cervical/cranial MR angiographies on all subjects. In this study, SCI was defined as a focal lesion >5 mm in diameter that was prolonged on both T2-weighted and proton density images. RESULTS: SCIs in the WM and/or BG were detected in 88 (40.2%) of the 219 subjects. No SCI >15 mm was observed in this series. Fifty of the subjects had SCIs only in the WM, 32 subjects had SCIs in both the WM and BG, and 6 subjects had SCIs only in the BG. Thus, 82 (93.2%) of 88 subjects with SCIs had lesions in the WM. Most subjects with SCIs in the BG also had SCIs in the WM. Multiple logistic regression analyses revealed that age, female sex, and hypertension were significant and independent predictors of SCIs in the WM, and that age, a history of ischemic heart disease, and carotid artery stenosis were significant and independent predictors of SCIs in the BG. CONCLUSIONS: The present study indicated that the relevant risk factors for SCIs in the WM and those for SCI in the BG were different. Our results suggest that SCIs are prone to first appear in the WM in association with aging and hypertension, and the additional appearance of SCIs in the BG predicts a progression of generalized atherosclerosis that is manifested in the carotid and coronary arteries.