Films of cuprous chloride (CuCI), a zinc-blende semiconductor lattice-matched to Si, were deposited by molecular beam epitaxy onto a room-temperature Si(111)-7x7 substrate and studied with surface-sensitive spectroscopies. Low-energy electron diffraction revealed an ordered 1x1 pattern at several monolayers coverage and Auger electron spectroscopy yielded an approximate Cu to Cl surface stoichiometry of one-to-one for as-deposited films. Ion scattering experiments indicated that the initial stage of CuCl growth involved Cl-Si bonding. Annealing the films initiated chemical reactions, which resulted in the loss of Cl and the formation of a Cu silicide. GRA N91-12365# Rutgers- The State Univ., New Brunswick, NJ. MAGNETIC PROPERTIES OF THE ELECTRON-DOPED G. Liang, J. Chen, M. Croft (Rutgers Univ., Piscataway, NJ.), K. V. Ramanujachary, and M. Greenblatt 1 Jun. 1990 11 p Submitted for publication (Contract N00014-82-K-0317; NSF DMR-87-14072) Magnetic susceptibility and magnetization data are presented for Nd(2-x)Ce(x)CuO(4-sigma) system. The Nd-local moments are seen to be crucial in interpreting the magnetic response. Evidence for a pervasive diamagnetic component (onsetting near 24 K) in the low field response which is sharply maximized near x=0.16 is presented. GRA can Following the discoveries of high temperature superconductivity in the rare earth copper oxide systems at 40 K by Bednorz and Muller in 1986 and at 90 K by other researchers in 1987, Sheng and Hermann, in 1988, discovered superconductivity in the thallium-alkaline-earth copper oxide systems with critical temperatures as high as 120 K. All of the TI-based compounds be described by the general formula, TI(m)A2Ca(n-1)CuO2(n+m+2), where m=1 or 2; n=5; A=Ba, Sr. For convenience, the names of these compounds are abbreviated as 2223 for TIBA2Ca2Cu3010, where each number denotes the number of TI, Ba(Sr), Ca and Cu ions per formula, respectively. The compounds with m=1 and m=2 are usually referred to as single and double TI-O layered compounds, respectively. The highest superconducting transition temperature known so far was found in TI2BaCa2Cu3010 at 125 K. GRA N91-12367# Michigan Univ., Ann Arbor. Dept. of Electrical Engineering and Computer Science. HIGH SPEED DEVICES BASED ON LATTICE MATCHED AND PSEUDOMORPHICALLY STRAINED QUANTUM WELLS FOR OPTOELECTRONIC INTEGRATED CIRCUITS Progress Report, 1 May - 31 Jul. 1990 Pallab Bhattacharya 31 Jul. 1990 8 p (Contract N00014-90-J-1831) (AD-A225052) Avail: NTIS HC/MF A02 CSCL 20/12 The main objectives are to develop InP-based lattice-matched and pseudomorphic quantum well materials using the MBE and TWO-PHOTON ABSORPTION CHARACTERIZATION OF HgCdTe Final Report, 28 Aug. 1987 - 27 Jun. 1990 Chris L. Littler and David G. Seiler 30 Jul. 1990 103 p (Contract DAAB07-87-C-F094; DA Proj. 1L1-61102-A-31-B) (AD-A225086; NV-90-14) Avail: NTIS HC/MF A06 CSCL 09/1 Magneto-Optical measurements of Hg(1-x)Cd(x)Te alloys have provided a new means of studying impurities and defects in this important II-VI material. Two-photon magnetoabsorption (TMPA) was used to accurately determine the temperature dependence of the energy gap of various HgCdTe alloys, revealing behavior that deviates from currently accepted models. In addition, magnetooptical techniques were used to detect the presence of both shallow and deep impurities/defects and accurately determine their activation energies, thus providing information necessary for understanding the electrical and optical properties of the material. GRA N91-12369# Parke Mathematical Labs., Inc., Carlisle, MA. The development of new or adaptation of existing methods for the preparation, growth and characterization of III-V electronic and optoelectronic materials for MOCVD technique was examined. Investigations were conducted on the growth of epitaxial layers using organometallic chemical vapor deposition method of selected III-V materials which are potentially useful for photonics and microwave devices. GRA N91-12370# California Univ., Santa Barbara. Dept. of Electrical and Computer Engineering. INVESTIGATION OF InP PROCESSING TECHNIQUES FOR DEVICE APPLICATIONS Final Technical Report, Feb. 1985 Sep. 1987 James L. Merz Jan. 1990 31 p (Contract F19628-85-K-0035; AF Proj. 2306) (AD-A225090; RADC-TR-89-326) Avail: NTIS HC/MF A03 CSCL 20/2 The emphasis was strongly oriented towards the overall technology of InP for photonic and other device applications. These investigations include such important and diverse subjects as the use of Rutherford backscattering (RBS) to study the solid phase epitaxial growth of InP after amorphization by heavy implant doses, the formation of a novel insulator in InP for passivation, the metallurgy of the traditional AuGe/Ni/Au contact for n-type InP and an analysis of the annealing of such contacts during the short times involved in RTA, the use of electrochemical profiling techniques to determine non-uniform implant distributions into InP, and the diffusion of the deep Fe trap in semi-insulting InP substrates as a result of standard thermal treatments. Significant progress was made in all of these areas. GRA N91-12371# Case Western Reserve Univ., Cleveland, OH. Dept. of Physics. NANOMECHANICS OF THIN FILMS Annual Technical Report Jun. 1990 9 p (Contract N00014-89-J-1555) (AD-A225180) Avail: NTIS HC/MF A02 CSCL 20/2 The work on the nanomechanics of thin films and microfibriles and interfaces is proceeding in a three-pronged approach, concentrating on deposited films and interfaces. The goal was to examine the structure property relations for mechanical properties in aluminum and aluminum oxide multilayers. Briefly the aluminum films have been deposited in various thicknesses in Ultra-High Vacuum (UHV) by evaporation from a W source and subsequently examined by AES, TEM and other surface analyses. For the mechanical data free standing aluminum films were formed by stripping in water from Victawer (R) edge coated thin glass slides following earlier published techniques. Thin aluminum films were deposited at room temperature by physical vapor deposition in UHV for mechanical testing. The film thickness ranged from 20 to 600 nm. Auger Electron Spectroscopy (AES) showed pure aluminum in the bulk, and a naturally formed layer of amorphous A1203, with a thickness of 3 to 5 nm, on the surface. Transmission Electron Microscopy (TEM) of these specimens showed the average grain size to vary proportionally with thickness. The samples ranged from 2 to 5 nm in length and 150 um in width. These Al films, like most deposited films, exhibited brittle behavior when strained uniaxially until fracture. It is also observed that the failure is intergranular. In an attempt to identify the mode of embrittlement, AES was used to investigate impurities at grain boundaries and the fracture edge. GRA Presented at the 6th General Conference of the European Physical Society, Amsterdam, Netherlands, 3-7 Sep. 1990 (Contract DE-AC06-76RL-01830) (DE91-000150; PNL-SA-18025; CONF-900903-1) Avail: NTIS HC/MF A03 Cooled Optically Stimulated Luminescence (COSL) in CaF2:Mn is an ionizing radiation dosimetry method recently developed at the Pacific Northwest Laboratory (PNL). In this method CaF2:Mn crystals irradiated by gamma radiation at room temperature are cooled to liquid nitrogen temperature (77 K), stimulated by ultraviolet laser light at 326 nm, and allowed to warm to room temperature. Light emission proportional to the gamma exposure occurs as the TLD warms from liquid nitrogen temperature to room temperature. The new method is an example of a highly sensitive phototransfer technique which could form the basis for future radiation dosimetry applications. Measurements to date have shown high potential for measuring gamma exposures in the range of 10 microR. The high sensitivity of the COSL technique is due in part to the larger quantum efficiency of radiative recombination at low temperatures and to the complete absence of the incandescent background associated with conventional thermoluminescent readout methods. Along with the potential for a system which is more sensitive than thermoluminescent readers, multiple COSL readouts can be performed with minimal reduction in the COSL intensity. The multiple readout capability can serve as a possible permanent dosimetry record, thus allowing the reanalysis of a questionable reading. In an attempt to optimize the sensitivity of the COSL method, a new readout system is being developed. N91-12373# Lawrence Livermore National Lab., CA. SHOCK COMPACTION OF HIGH-T(SUB c) SUPERCONDUCTORS DOE 15 p S. T. Weir, W. J. Nellis, P. C. McCandless, W. F. Brocious, C. L. Results are presented for shock compaction experiments on high-(Tc) superconductors and describe the way in which shock consolidation addresses critical problems concerning the fabrication of high J(sub c) bulk superconductors. In particular, shock compaction experiments on YBa2Cu307 show that shock-induced defects can greatly increase intragranular critical current densities. The fabrication of crystallographically aligned Bi2Sr2CaCu208 samples by shock-compaction is also described. These experiments demonstrate the potential of the shock consolidation method as a means for fabricating bulk high-(Tc) superconductors having high critical current densities. DOE N91-12374# Universiteit Twente, Enschede (Netherlands). A CONTRIBUTION TO THE UNDERSTANDING OF ac LOSSES (ISBN-90-9002966-4; ETN-90-97764) Copyright Avail: NTIS Current distribution, losses and voltage current relations of superconducting filaments, wires and cables, are discussed. Numerical models are derived for filaments for reducing Maxwell's equations to a Poisson equation in terms of the vectorpotential. Panel method and an iteration process is used for solving. Accurate expressions for the magnetization, voltage current relation and losses for circular, square and hollow filaments are derived. Non-zero filament radii do not appear to differ greatly from zero filament radii. For computation in cables, the constitutive relation of wires is assumed to be linear, and independant of place, time and local components of the electromagnetic field. Losses for a square cable appear to be smaller than losses for a circular cable, with equal perimeter, and placed in the same applied field. ESA 1990 Pekka A. Huttunen Finnish Academy of Technology 37 p Sponsored by Emil Aaltonen Foundation (Ph-166; ISBN-951-666-305-2; ISSN-0355-2721; ETN-90-97976) Avail: NTIS HC/MF A03 A monoenergetic positron beam, operated under ultrahigh vacuum, was utilized to examine the interaction mechanisms of a positron at the vacuum-solid and the solid-solid interfaces. The positron surface processes and the underlying mechanisms are studied by monitoring their temperature and energy dependencies. Different fundamental aspects influencing positron motion at an interface of two materials are discussed. Positron energy loss mechanisms at the final stages of thermalization and thermal positron motion in the solids are studied. The positron diffusion is applied to extract defect profiles in heteroepitaxial structures. from Vestnik Leningradskogo Universiteta (USSR), no. 16, 1971 p 143-145 (AD-A225260; FTD-ID(RS)R-0582-90) Avail: NTIS HC/MF A03 CSCL 09/1 The conditions of Au crystal production on W field emitter were studied by the field emission microscope. The results have shown that microfield emitter increases field emission and its stability. The significance of transition layers on a metal substrate for crystallization is discussed. Wide use of method of autoelectronic microscopy both in research and in practical region requires together with use of high melting materials, decontaminated with heat treatment, expansion of wheel/circle of substances, suitable for use as autocathodes. Under ice, to a considerable degree, it was possible to achieve the complete auto-emission current from whiskers, grown from the vapors under high vacuum conditions. By this method together with the desorption by field are obtained the auto-emitter, which give the symmetrical picture of surface, and for the materials with the low melting point, in particular gold. Obtaining field emission current from the projections of low melting substances to the surface of point is proposed. GRA N91-12378# Litton Systems, Inc., Charlotte, NC. Airtron Div. CONTRACT CRYSTAL GROWTH AND FABRICATION SERVICES Quarterly Technical Report No. 5, May - Jul. 1990 J. E. Creamer, R. C. Acklin, and M. H. Randles 7 Aug. 1990 2 p (Contract N00014-89-C-2222) (AD-A225381) Avail: NTIS HC/MF A01 CSCL 20/2 This program is intended to give the scientists at the Naval Research Laboratory the ability to evaluate new solid state laser crystals. During the fifth quarter of this contract only one growth run was performed, the tenth since project start. The crystal requested and grown was Er, Tm:YAG. It was assumed that the distribution coefficients are unity and that the crystal composition GRA will be the same as the melt. N91-12379# Massachusetts Inst. of Tech., Cambridge. Microsystems Technology Labs. MECHANICAL PROPERTIES OF MICROELECTRONICS THIN FILMS: SILICON NITRIDE (Si3N4) Fariborz Maseeh, Miles Arnone, and Stephen D. Senturia Oct. 1989 79 p LIMITED REPRODUCIBILITY: Availability: Document partially illegible (Contract MDA972-88-K-0008; ARPA Order 6510) Mechanical design of microfabricated devices requires knowledge of mechanical material properties. Thin film material properties are sensitively process dependent, and should therefore be organized accordingly. A relational database of material properties is under development as part of a general micro-electro-mechanical computer aided design environment. A computerized literature search through the published values for Silicon Nitride (Si3N4) properties under various processing conditions resulted in the following document. GRA N91-12380# Massachusetts Inst. of Tech., Cambridge. Microsystems Technology Labs. MECHANICAL PROPERTIES OF MICROELECTRONICS THIN FILMS: SILICON DIOXIDE (SIO2) Fariborz Maseeh, Sean M. Gelston, and Stephen D. Senturia Oct. 1989 69 P (Contract MDA972-88-K-0008; ARPA Order 6510) Mechanical design of microfabricated devices requires knowledge of mechanical material properties. Thin film material properties are sensitively process dependent, and should therefore be organized accordingly. A relational database of material properties is under development as part of a general micro-electro-mechanical computer aided design (CAD) (DLR-Mitt-90-11; ISSN-0176-7739; ETN-90-98049) Copyright Avail: NTIS HC/MF A03; DLR, VB-PL-DO, Postfach 90 60 58, 5000 Cologne, Fed. Republic of Germany, HC 13 Deutsche marks The structure and principle of a data collection system for a Bridgeman control apparatus are described. Measuring instruments and control units from different producers were integrated in this system. With two computers it was possible to measure and modify important process parameters such as temperatures, cooling rate, gas pressure and pulling rate during the whole growth process. Measurements were made with this system to characterize time dependent convections in the melt. A totally automated crystal ESA growth is possible. 77 THERMODYNAMICS AND STATISTICAL PHYSICS Includes quantum mechanics; theoretical physics; and Bose and Fermi statistics. For related information see also 25 Inorganic and Physical Chemistry and 34 Fluid Mechanics and Heat Transfer. N91-12382# Joint Inst. for Nuclear Research, Dubna (USSR). ILLUSTRATIONS FROM THE COLLECTION QUANTUM B. N. Zakharev and E. B. Plekhanov 1989 18 p In RUSSIAN; The graphs are given which elucidate the important quantum features: How variations of spectral parameters (positions of energy levels or R-matrix resonances and normalizing constants or reduced widths) affect the form of potentials; bound states embedded into the continuum spectrum and comparison of one-channel and two-channel models; resonance tunneling through a system of identical barriers and transfer to the limit of the infinite periodical lattice; and accumulation of errors in process of integration of differential equations in finite-difference approximation. The illustrations are accompanied by comments. DOE N91-12383# Centro Brasileiro de Pesquisas Fisicas, Rio de INHOMOGENEOUS TWO-FLUID COSMOLOGIES WITH M. A. S. Nobre (Universidade Federal do Rio de Janeiro, Brazil ) (DE90-634868; CBPF-NF-072/88) Avail: NTIS (US Sales Only) HC/MF A03 A new class of exact expanding inhomogeneous solutions of the Einstein-Maxwell equations is derived. These solutions generalize the dust filled models found by Ruban and the Doroshkevich magnetic universes. In the most general case the cosmological constant is non-zero and the matter content is a mixture of two interacting perfect fluids plus a sourceless electromagnetic field. The influence of the field near the singularity and at the latter stages of the expansion is examined. A subclass of the models approaches homogeneity and isotropy for large cosmological times. DOE N91-12384# Bonn Univ. (Germany, F.R.). Inst. fuer Physik. CLASSICAL AND QUANTUM MECHANICAL ASPECTS OF THE NONLINEAR DYNAMICS OF PERIODICALLY DRIVEN SYSTEMS Thesis [KLASSISCHE UND QUANTENMECHANISCHE ASPEKTE DER NICHTLINEAREN PERIODISCH GETRIBENER SYSTEME] Heinz-Peter Breuer Apr. 1990 105 p In GERMAN (Bonn-IR-90-14; ISSN-0172-8741; ETN-90-97904) Avail: NTIS HC/MF A06 The fundamentals of adiabatic motion and of the interconnected quantum holonomy in systems which are described through periodical time dependent Hamilton, operators, are discussed. A classical examination in the field of nonlinear dynamics of periodically driven, nonharmonic oscillators is conducted. ESA 80 SOCIAL SCIENCES (GENERAL) Includes educational matters. No abstracts in this category. 81 ADMINISTRATION AND MANAGEMENT Includes management planning and research. N91-12385*# Houston Univ., Clear Lake, TX. Research Inst. for Computing and Information Systems. 78 P SPACE MARKET MODEL DEVELOPMENT PROJECT (NASA-CR-187249; NAS 1.26:187249) Avail: NTIS HC/MF A05 CSCL 05A The objectives of the research program, Space Market Model Development Project, (Phase 1) were: (1) to study the need for business information in the commercial development of space; and (2) to propose a design for an information system to meet the identified needs. Three simultaneous research strategies were used in proceeding toward this goal: (1) to describe the space business information which currently exists; (2) to survey government and business representatives on the information they would like to have; and (3) to investigate the feasibility of generating new economical information about the space industry. Author N91-12386# Navy Personnel Research and Development Center, San Diego, CA. READINGS ON MANAGING ORGANIZATIONAL QUALITY Final Report, Apr.- Nov. 1989 Nida Backaitis, ed. (University of Southern California, Los Angeles.) and Harold H. Rosen, ed. May 1990 327 P Sponsored by Office of the Under Secretary of the Navy, Washington, DC (AD-A224888; NPRDC-TN-90-19) Avail: NTIS HC/MF A15 CSCL 05/1 New management philosophies are examined which are helping to bring about the transformation of American industry and that are enabling firms to meet competitive challenges successfully with novel strategies. The new management philosophy is based on assumptions that better reflect the ground rules of today's global economy than do the assumptions upon which much of current management practice is based. The role is emphasized of leadership at various levels of the organization in bringing about effective organizational response to the new competitive challenge. It describes changes in policies, in organizational structure, in the management of relationships with customers and suppliers, and Avail: Univ. Microfilms Order No. DA9023796 An artificial intelligence approach is adopted in investigating the online information retrieval activity and in studying the design of online information retrieval systems. The initial approach was to investigate the interactions between the searcher and the retrieval system and the searcher and the reference librarian. The objective was to develop cognitive models of these processes that will provide a sound basis for incorporating search assistance into an online system. This research consisted of three stages: an empirical investigation stage, a system building stage, and a system testing stage. During the empirical investigation stage, two cognitive psychology based empirical studies were conducted in which the searcher/librarian and the searcher/system interactions were observed. Some important findings from these studies were derived: (1) a taxonomy of misconceptions users have about the subject area, the system and the classification scheme, (2) five online search strategies were developed, and (3) an empirically based process model for assisting searchers in refining their queries was developed. At the system building stage, a blackboard architecture was adopted for the prototype system where the proposed capabilities (alleviating searchers' misconceptions, selecting appropriate search strategies, and refining searchers' queries) were incorporated. This system was created using Lisp and Flavors. The system was tested against an existing online catalog in a laboratory experiment and the prototype system out-performed the existing online catalog in search recall and satisfaction level. This research suggests that a knowledge-based information retrieval system armed with the appropriate search heuristics, the knowledge about the subject area and the classification scheme, and the query refinement mechanisms can become more responsive, intelligent, and capable of providing interactive support of a variety of users. Dissert. Abstr. N91-12389 Sussex Univ., Brighton (England). A RELATIONAL DATABASE FOR CARTOGRAPHIC MAP DISPLAYS Ph.D. Thesis Robert Daly 1988 294 p Avail: Univ. Microfilms Order No. BRDX89823 The storage of cartographic data on computer database systems is presented. The design and implementation of a relational database system are described. The system is primarily intended to support the retrieval of map data with emphasis being placed on high accuracy, speed and flexibility. Data is expected in a vectorized form and output is intended for color raster displays. The models which may be used to represent map data are examined and some interesting scale-free line and surface structures are presented. The section on data modelling discusses the contrasting requirements of line-based and area-based problems and the relative merits of regular and irregular representations. The model adopted as a general-purpose database incorporates an irregular vector structure, a scale-free quadtree-based surface structure, and a hierarchical feature description scheme. A grid partitioning is also considered necessary for indexing, for supporting enclosure and color infill operations. Within the database system, RDBASE, emphasis is placed on powerful indexing structures, high portability, integrated metadata, providing a bulk data storage facility for coordinate strings, and integrating structured query language (SQL) queries with a functional interface. Various indexing methods are described. Extensions to the B+tree method are presented which enable the handling of repeated values and combinations of attributes, and also support query optimization costing functions and unique identifier generation. Problems involving relational representations of network structures are used to identify the need for a functional interface to the database. The developed interface incorporates two levels: an efficient low level and a SQL-based high level. The latter incorporates an interesting implementation of the decomposition method for its query optimization. Dissert. Abstr. INTERNATIONAL ENERGY: SUBJECT THESAURUS The International Energy Subject Thesaurus contains the standard vocabulary to indexing terms (descriptors) developed and structured to build and maintain energy information databases. Involved in this cooperative task are (1) the technical staff of the USDOE Office of Scientific and Technical Information (OSTI) in cooperation with the member countries of the Energy Technology Data Exchange (ETDE), and (2) the International Nuclear Information System (INIS) staff representing the more than ninety countries and organizations recording and indexing information for the international nuclear information community. ETDE member countries are also members of the International Nuclear Information System (INIS). Nuclear information indexed and recorded for INIS by these ETDE member countries is also included in the ETDE Energy Data Base, and indexing terminology is therefore cooperatively standardized for use in both information systems. This structured vocabulary reflects the scope of international energy research, development, and technological programs and encompasses terminology derived not only from the basic sciences but also from the areas of energy resources, conservation, safety, environmental impact, and regulation. N91-12391 Maryland Univ., College Park. DOE THE ANALYSIS AND DESIGN OF CONCURRENCY USING BOX STRUCTURES Ph.D. Thesis Shirley Ann Becker 1990 312 p Avail: Univ. Microfilms Order No. DA9030848 This research extends the existing box structure theory by defining the syntactic signatures and syntax of concurrency so that a correct concurrent design is attainable. Concurrency is characterized in terms of process interaction, process synchronization, and process interruptions, so that syntactic signatures and syntactic descriptions of deterministic and non-deterministic concurrency can be defined. Guidelines for the analysis and design of new and existing concurrent system environments are presented. A white box structure is developed to describe potential concurrent designs that must be validated for correctness and completeness. Correctness and closure verification procedures are specified for deterministic concurrent system designs, and correctness and closure validation procedures were specified for non-deterministic concurrent system designs. A verification procedure for deterministic white box structures applied the abstract syntax method of verification. A validation procedure for non-deterministic white box structures defined the transformation of a white box structure into a petri-net graph for validation of correctness and closure properties associated with the petri-net. Performance issues associated with concurrent designs were also addressed so that the efficiency of alternate clear box designs could be assessed. An automated petri-net tool called P-NUT was used in our research to gather feedback about system performance. The box structure extensions were demonstrated in a case study on the analysis and design of concurrency in a complex system environment. The case study illustrated the application of the concurrency semantics and syntax as well as the correctness and closure process for deterministic and non-deterministic concurrent system designs. Dissert. Abstr. N91-12392 East Anglia Univ., Norwich (England). A. T. C. Wood-Harper 1989 246 p The confusion in the choice of methodologies which support the definition of an information system prior to development and installation is identified. In order to alleviate this confusion a comparison of these methodologies is made and concludes: that no single approach is best or sufficient; that any approach should support organization activities and handle the data analysis perspective; and, that any method should make a contextual analysis of the environment. Consequently, this insight was used to identify generic approaches and then they were classified. After this classification a synthesis is made and this framework is expanded to a methodology called Multiview. For further clarity this methodology is then used for fieldwork consisting of six action research cases to accumulate the following lessons: the problem situation and the initial terms of reference; the problem solving team; action; methodology products and processes; and the theory of using the Multiview methodology for defining an information system. Finally, these lessons are used to make the following conclusions: that the methodology needed improvements; in defining an information system there is a minimum set of contingencies consisting of problem solver, the situation and the methodology; and also that the definition process can be considered as a social process which can be explained by social theories. From the above conclusions recommendations are made to improve the Multiview methodology, to research the contingencies, and to formulate a framework for the problem solver to create a unique method relevant to the situation. |