IC Structures Research Articles

A comprehensive study of the X-ray structure and spectrum of IC 443

view Abstract Citations (95) References (61) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Comprehensive Study of the X-Ray Structure and Spectrum of IC 443 Petre, R. ; Szymkowiak, A. E. ; Seward, F. D. ; Willingale, R. Abstract This paper presents the results of a comprehensive study of the X-ray emission from the supernova remnant IC 443, using the solid state spectrometer, IPC, and high-resolution images of the Einstein Observatory, and the medium-energy detector of the HEAO 1 A-2 experiment. A soft X-ray appearance was observed, highly atypical of a supernova remnant in the adiabatic phase, with little correlation between X-ray and optical or radio features. The best-fit models of the low-energy X-ray spectrum of the brightest area of the remnant suggest either that the remnant has not yet attained ionization equilibrium or that the X-rays arise in a multiphase medium. Pronounced soft X-ray spectral differences across the remnant are accounted for by variations in absorption by an intervening molecular cloud. The analysis suggests that, despite the atypical X-ray appearance, the X-ray emission in IC 443 is probably confined to a thin (0.1 pc) shell. Publication: The Astrophysical Journal Pub Date: December 1988 DOI: 10.1086/166922 Bibcode: 1988ApJ...335..215P Keywords: Astronomical Spectroscopy; Supernova Remnants; X Ray Sources; H Ii Regions; Molecular Clouds; Spectrophotometry; Stellar Envelopes; Astrophysics; NEBULAE: INDIVIDUAL ALPHANUMERIC: IC 443; NEBULAE: SUPERNOVA REMNANTS; X-RAYS: SOURCES full text sources ADS | data products SIMBAD (1)

Uniform and abrupt InGaP/GaAs selectively doped heterostructures grown by MOVPE for HEMT ICs

Uniform and abrupt Si-doped InGaP/GaAs selectively doped heterostructures are grown by atmospheric-pressure metalorganic chemical vapor deposition, and the feasibility of the material system for HEMT ICs is demonstrated for the first time. The uniformities of donor concentration and thickness of Si-doped InGaP layers are ±4.5% and ±1.5%. These values are small enough for IC applications. The mobility at 4.2 K and the two-dimensional electron gas concentration obtained from Shubnikov-De Haas oscillation measurements are 89,300 cm2/V·s and 8.9×1011 cm−2 for samples with a spacer thickness of 5.5 nm. HEMT IC structures were grown to evaluate the device characteristics. It was shown that enhancement- and depletio-mode HEMTs can be fabricated on the same wafer by selective etching technique. The characteristics of the transistors exhibit no instability at 77 K.

The shapes and shaping of the planetary nebulae IC 3568, NGC 40, and NGC 6543

Radio and optical images of three compact planetary nebulae, NGC 6543, IC 3568, and NGC 40, are found to reveal a variety of morphological and ionization signatures of wind shaping and heating. Both NGC 6543 (one of the most morphologically complex planetaries in the sky) and IC 3568 (one of the simplest) exhibit large density changes on size scales corresponding to sound-crossing times of about a century, arguing that the density gradients are sustained by shocks driven by stellar winds. All of the available data show the structure and ionization of IC 3568 to conform to simple hydrodynamic models of nebulae that are shaped by interior stellar winds. NGC 6543 also shows very local changes in optical line ratios that are best understood in the same manner. 34 references.

Ultrasonic investigations of incommensurate Rb2Zncl4

Abstract Elastic properties of Rb2Zncl4 were investigated by measuring the velocity and attenuation of both, transversal and longitudinal ultrasonic waves propagating along the crystallographic axes. At the lock-in phase transition temperature only v44 shows a remarkable anomaly. This anomaly has been found to be asymmetric with respect to the interchange of oscillation and propagation direction of the transverse ultrasonic wave. The anomaly of v44 at Tc is proportional to the contents of commensurate regions in the IC structure. From the temperature dependence of ultrasonic velocities at the phase transition from paraelectric to IC phase the critical behaviour of the order parameter should correspond rather to the (n = 2)-Heisenberg-model than to the Ising model.

Analysis of microwave characteristics of photoconductive IC structures

A one-dimensional analytic solution for the microwave photoresponse of an optically modulated semiconductor channel is presented. This extends the existing treatments by including the effects of nonuniform channel cross sections and conductivity, nonuniform optical illumination, field-dependent mobilities, nonzero dielectric relaxation times, arbitrary electrical and optical excitation frequencies, and full coupled bipolar carrier transport. The solution is continuous over the full range of electric field intensities and thereby describes both the saturated and nonsaturated regimes of the photocurrent. Only the low-level generation case is considered, and trapping effects and diffusion are not included. This model allows the effects of optical stimulation in many typical IC structures to be assessed from dc up through the microwave range of frequencies.

Flute an Expert Floor Planner for Full-Custom VLSI Design

Flute is a heuristic floorplanner that operates as part of Cadre, a system of cooperating expert agents for converting a hierarchical structural description into full-custom VLSI layout. Flute is modeled on the human floorplanning process and uses a mixture of rule-based programming, state control, and algorithmic operators. Initially, a topological plan is generated by placing modules on a grid graph. From this plan, a constraint graph is prepared. This graph is solved to add geometric size and placement information to the floorplan. Though Flute handles a fairly small number of submodules at a time, it can construct a floorplan of complex VLSI layout using a hierarchical structure of ICs. Flute is implemented in Zeta-lisp on Symbolics Lisp machines.

A CD-ROM Data Retreiver IC

The functional structure of a programmable CD-ROM data retreiver IC is discussed here. The chip operates on serial streams of CD data from an already available EFM demodulator/decoder chip, designated here as CD2A, and performs a number of data manipulations such as; descrambling, reformatting and CRC error checks, etc. The chip can be programmed to locate and transfer desired data blocks and/or bytes to a host processor through an I/O bus interface. Slow serial data transfers, e.g. RS232, can also be performed, if needed by utilising the appropriate facilities of the system's microcontroller.

A new CMOS IC structure and its characterization

In this paper a new N-channel MOS transistor structure providing the improvement of electrical characteristics with respect to the conventional structure and simplified fabrication compared to generally accepted drain extension structure is presented. Description and optimisation of technologycal procedure for fabrication of the new N-channel MOS transistor structure are given. Also, static and dynamic characteristics of the N-channel MOS transistor realized by new procedure are investigated and compared to the corresponding characteristics of N-channel MOS transistors realized by conventional and drain extension procedures. Finally, reliability of the CMOS ICs realized by new procedure is investigated using both static and dynamic life tests.

Current status of ion implantation equipment and techniques for semiconductor IC fabrication

The status of the use of ion implantation for IC fabrication is described in terms of the history of ion implantation system sales, operating regions for beam currents and energies and new applications for advanced IC structures. Key aspects of process limiting effects such as charging, heating, channeling, particle contamination and uptime are discussed. New technologies such as MeV implantation, direct formation of buried dielectric layers, focused ion beams and advances in the use of computer controls are described.

Some recent developments in low-voltage e-beam testing of IC's

With the increasing complexity and decreasing dimensions of IC structures, traditional mechanical probing techniques to determine voltage waveforms at specific locations within a device can no longer be applied. This is due to the difficulties of positioning a mechanical probe on features approaching one micron width, and the capacitive loading of the device under test which distorts the measured waveforms and in some instances causes the device to malfunction. These problems are all avoided, if the mechanical probe is replaced with an electron probe. An additional advantage is that the danger of device damage is avoided if a non-loading beam energy, typically in the range from 500-3,000eV, is selected.While the electron probe diameters used for device testing are large by normal SEM imaging standards (typically 0.1-0.5 microns), current levels require to be as large as possible (typically 10-7 - 10-8A). This is especially necessary in some of the more important operating modes where the incident electron beam is pulsed, resulting in a substantial reduction in average current levels compared to continuous beam operation.

High Resolution X-ray Images of Puppis a and IC 443

We present soft X-ray photomosaic images of two supernova remnants, Puppis A and IC 443, constructed from a series of exposures by the Einstein imaging instruments. The complex morphologies displayed in these images reflect the interaction between “middle-aged” supernova remnants and various components of the interstellar medium. Surface brightness variations across Puppis A suggest that inhomogeneities on scales from 0.2 to 30 pc are present in the interstellar medium, while the structure of IC 443 is apparently dominated by the interaction between the remnant and a giant molecular cloud.

Off Line, Built-in Test Techniques for VLSI Circuits

It is shown that the use of redundant on-chip circuitry improves the testability of an entire VLSI circuit. In the study described here, five techniques applied to a two-bit ripple carry adder are compared. The techniques considered are self-oscillation, self-comparison, partition, scan path, and built-in logic block observer. It is noted that both classical stuck-at faults and nonclassical faults, such as bridging faults (shorts), stuck-on x faults where x may be 0, 1, or vary between the two, and parasitic flip-flop faults occur in IC structures. To simplify the analysis of the testing techniques, however, a stuck-at fault model is assumed.

Dual Column Wafer Inspection SEM

With the trend in the semiconductor industry towards smaller and smaller IC structures, there is a growing requirement for visual inspection systems with resolution beyond that of the optical microscope. Further requirements are that wafers up to 6" can be handled, and that any part of the wafer be viewed at normal incidence and tilted at angles up to about 60° with a provision for rotating the specimen about the center of the field of view. The system must neither contaminate the wafer, nor damage it in any way.General purpose scanning electron microscopes have found limited application in wafer inspection for a number of years. These instruments, however, have satisfied only some of the requirements listed above. In particular, the requirement to tilt large wafers to angles as high as 60° has required operation at long working distances with resultant poor image resolution, especially at low accelerating voltage. A further major limitation has been the inability to rotate the wafer about the center of the field of view at all viewing locations.

150 V High Voltage Linear IC Technology

A new structure, called a Semi-Well Isolation (SWI) IC structure, suitable for high voltage IC and its process technologies are developed for 150 V consumer ICs. The SWI structure has an epitaxial layer of two different thicknesses, and different impurity profiles if desirable. High voltage elements are formed in the thick portion, the isolation region and small signal elements are formed in the thin portion. As results, both high voltage transistors and low voltage ones are optimized separately on the same chip. A color TV vertical deflection output IC, which operates from a transformerless voltage source, is developed using the SWI structure.

Structure of liquid alkali metals as electron-ion plasmas

Pscudopotent ial calculations of the stat ic structure factor S(k) of simple liquid nletals involve the construction of an effective ion-ion potent ia l through linear screening of each bare ion by a homogeneous electron gas. The basic assumption made at this step of the theory is tha t the bare electron-ion coupling is weak and the screening clouds of different ions do not interfere with each other. To the extent that this assumption is true, the final result ought to be equivalent to tha t of an elech~on-ion plasma (EIP) approach, in which the structure of the l iquid metal is directly obtained from the structure of a bare ionic p lasma l inearly screened by a homogeneous electron gas. That is (1,~)

Hybrid IC structures using solder reflow technology: Tsuneaki Kamei, Masanori Makamura, Hisashi Ariyoshi and Masanobu Doken IEEE Trans. Components, Hybrids, Mfg Technol. Chmt-2, (2) 208 (June 1979)

Hybrid IC structures using solder reflow technology: Tsuneaki Kamei, Masanori Makamura, Hisashi Ariyoshi and Masanobu Doken IEEE Trans. Components, Hybrids, Mfg Technol. Chmt-2, (2) 208 (June 1979)

Novel IC Structure for 150V High-Voltage Consumer IC

This paper describes a novel IC structure and its fabrication process for 150V high voltage consumer ICs. A color TV vertical deflection output IC which operates with a transformerless voltage source has been developed.

Hybrid IC structures using solder reflow technology: T. Kamel, N. Nakamura, H. Ariyoshi and M. Doken Proc. IEEE 28th Electron. Components Conf., Anaheim, 24–26 April 1978, p.172

Hybrid IC structures using solder reflow technology: T. Kamel, N. Nakamura, H. Ariyoshi and M. Doken Proc. IEEE 28th Electron. Components Conf., Anaheim, 24–26 April 1978, p.172

On the stereostructure of polystyrene samples obtained by extraction of isotactic polystyrene with butanone

Stereospecific f ract ionat ion of polymers is of special in terest in obtaining products of high stereoregular i ty. Extraction of highly stereoregular polystyrene has been described to be such a process and treatment of isotact ic polystyrene samples with boi l ing butanone which is supposed to be solvent for atact ic and a nonsolvent for iso tact ic polystyrene has been used in the quant i tat ive determination of the "atact ic content". ( I ) However so far no d i rect analysis of the stereostructure (2) of the extract has been performed to ver i fy the simple assignment of the f ract ional amount of extracted polymer to the f ract ional amount of atact ic structure.

The structure and content of IC 1613

view Abstract Citations (71) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The structure and content of IC 1613. Hodge, P. W. Abstract Results are reported for a combination of photoelectric surface photometry, photographic photometry, and star counts, which were performed to obtain information on the structure and content of IC 1613, the faintest of the nearby irregular galaxies of the Local Group. Isophotal contours derived from the photoelectric surface-brightness measures alone and from microphotometry of the photographic plates are presented, the galaxy's ellipticity is determined as a function of radius, orientation angles are derived from the isophotal diagrams, and integrated magnitudes are determined. The star counts are described, and equidensity contours are plotted and compared with the isophotes. Luminosity profiles are obtained, the galaxy's luminosity function is deduced, and the integrated color of IC 1613 is determined. Twenty stellar associations are delineated and found to be concentrated in the NE and NW quadrants in addition to the core. A total of 43 star-cluster candidates are located, of which 18 are considered fairly certain to be open star clusters. The dust content of IC 1613 is examined in a preliminary way, one relatively certain identification of a dust cloud is made, and 10 other possibilities are noted. Publication: The Astrophysical Journal Supplement Series Pub Date: May 1978 DOI: 10.1086/190522 Bibcode: 1978ApJS...37..145H Keywords: Astronomical Photometry; Galactic Structure; Interstellar Matter; Star Distribution; Astronomical Photography; Electrophotometers; Isophotes; Nebulae; Open Clusters; Photographic Plates; Astrophysics; Dwarf Galaxies:Stellar Content; Dwarf Galaxies: Structure full text sources ADS | data products SIMBAD (1) NED (1)