N89-29221# Associacao Latino-Americana de Metalurgia e Materiais, Rio de Janeiro (Brazil). PLASTIC DEFORMATION OF YBa2Cu307-x Gabriel Torres Villasenor and Jose E. Moreno 1988 7 p In (DE89-613395; INIS-BR-1531; CONF-8811214) Avail: NTIS (US Sales Only) HC A02/MF A01 The high temperature superconductor YBa sub 2 Cu sub 3 O sub 7-x shown a brittle behavior when deformed under ambient conditions. If a hydrostatic state of stress is imposed with a metal matrix, it is possible to induce exttended plastic deformations as a great as 200 percent were achieved using this method without loosing the superconductivity in the ceramic. The observed deformations mechanisms are similar to those observed in the superplastic metals and the boundary ceramic metal matrix was found to be highly coherent. This method opens a new technique that can be apllied in the manufacture of superconductor wire. N89-29222# DOE Associacao Latino-Americana de Metalurgia e Materiais, Rio de Janeiro (Brazil). FACTORS AFFECTING STRESS DISTRIBUTION AND DISPLACEMENTS IN CRYSTALS 3-5 GROWN BY CZOCHRALSKI METHOD WITH LIQUID ENCAPSULATION C. E. Schvezov, I. Samarasekera, and F. Weinberg 1988 20 p In SPANISH; ENGLISH summary Presented at the 3rd Latin-American Colloquium about Fatigue and Fracture of Materials, Rio de Janeiro, Brazil, 27 Nov. 1988 (DE89-613396; INIS-BR-1533; CONF-8811214) Avail: NTIS (US Sales Only) HC A03/MF A01 A mathematical model based on the finite element method for calculating temperature and shear stress distributions in 3 to 5 crystals grown by LEC technique was developed. The calculated temperature are in good agreements with the experimental measurements. The shear stress distribution was calculated for several environmental conditions. The results showed that the magnitude and the distribution of shear stresses are highly sensitive to the crystal environment, including thickness and temperature distribution in boron oxides and the gas. The shear stress is also strongly influenced by interface curvature and cystals radius. L. Samuelson, A. K. M. Rahman, G. P. Puglia, S. Clough, S. Tripathy, T. Inagaki, b0661237, X. Q. Yang, T. A. Skotheim, and Y. Okamoto (Polytechnic Univ., Brooklyn, NY.) 1989 10 P Presented at the International Conference on Intelligent Materials, Tsukuba, Japan, 1 Mar. 1989 Sponsored in part by ONR (Contract DE-AC02-76CH-00016) (DE89-012974; BNL-42655; CONF-8903128-1) A02/MF A01 Avail: NTIS HC Novel, self-assembled materials were designed and produced from first principle to possess unique structural hierarchy and electronic and optical properties. The Langmuir-Blodgett technique was used to study the molecular organization of a mixed 3-hexadecyl pyrrole (3HDP) and ferrocene-derivatized pyrrole (Fc-Py) surfactant system. The pyrrole moiety was chosen for its' well established electronic and optical properties when polymerized, while ferrocene, it is theorized, if properly oriented into a Langmuir-Blodgett monolayer film may show a layered array of transition metals which would be extremely valuable as a model for 2-D magnets. The ferrocene group may also provide the possibility of charge coupling between neutral ferrocene and oxidized ferricenium which could be controlled electrochemically or photochemically. It has been determined that stable monolayer films of the mixed system could be formed at the air-water interface. Water soluble organic salts comprise a class of crystalline materials containing many efficient harmonic generators for high power lasers. Statistical studies of the simple chiral salts reveal that approximately ten percent have nonlinearities similar to or better than potassium dihydrogen phosphate, the material most commonly used for high power frequency conversion. Furthermore, high damage thresholds (greater than 40 J/sq cm at 1.06 microns) have been demonstrated in 1-arginine phosphate which is a representative crystal from this class. Simple chiral salts have ultraviolet cutoff wavelengths of 200 to 500 nm, and this, together with the fact that many are very birefringent, implies that phasematching over a wide range of wavelengths should be possible. In particular, this class of materials may be expected to contain efficient harmonic generators of blue and ultraviolet light. Finally, very large single crystals (greater than 1000 cm) of many of these water soluble materials can be grown, making the fabrication of large aperture frequency conversion devices possible. DOE Low-energy, mass-separated ion beams of Ge, Ga, and As at 30 and 40 eV were used to deposit isotopically pure, epitaxial layers of Ge-76 and Ge-70 on GaAs(100) and of Ga(69)As and Ga(71)As on Ge(100). Epitaxial growth of Ge and GaAs layers was achieved at temperatures as low as 250 C. Growth of the compound GaAs was accomplished by repetitive magnetic switching between the Ga(+) and As(+) ion beams obtained simultaneously from a single ion source. The structure of the deposited layers is characterized by ion channeling, transmission electron microscopy, and X-ray diffraction. DOE cm at 55 keV. The response of these amorphous layers to post-implantation annealing in the temperature range from 700 C to 800 C was investigated by in situ Transmission Electron Microscopy (TEM) and conventional TEM of specimens annealed in bulk form. It was found that the amorphous Al2O3 transformed to the transitional gamma phase along an irregular front. The recrystallized material is columnar with the individual columns or domains irregular in size and shape. The alpha-Al2O3 is composed of two variants which are twin related and have the following orientation relationship with the substrate: <110> gamma <10 bar 10 alpha and 111 gamma 0001 alpha. The temperature dependence velocity of the amorphous-to-gamma transformation front was measured by in situ TEM. Assuming a thermally activated process, the activation energy has been determined from an Arrhenius plot of velocity versus T(-1). These results are discussed in terms of possible rate controlling processes of the transformation. DOE 15 P on Oxygen Disorder Effects in High Tc Superconductors, Trieste, Italy, 18 Apr. 1989 Prepared in cooperation with California Univ., Berkeley. Lawrence Berkeley Lab. (Contract DE-AC03-76SF-00098) (DE89-014893; LBL-27267; CONF-890480-1) Avail: NTIS HC A03/MF A01 = The compound YBa2Cu30(x) (1-2-3) was the first one whose superconducting transition temperature exceeded the technologically important temperature of 77K. Actually, the 1-2-3 7 became compound at close to oxygen stoichiometry z = superconducting at about T sub c 90K, with T sub c dropping by increments as z decreased from the value 7. In the 90K superconducting phase, occupied sites form O-Cu-O chains, and the resulting 3-D structure has orthorhombic symmetry. When available sites in the mirror plane are occupied statistically by O ions, the resulting structure has tetragonal symmetry and the material is nonsuperconducting. It thus appears that the tetragonal to orthorhombic transition in the 1-2-3 compound can be modeled by an order-disorder transition in the mirror plane. The properties of this transition are reviewed and appropriate phase diagrams pertaining to oxygen ordering in the plane are derived. Much pertinent information concerning oxygen ordering in 1-2-3 is reviewed in a recent paper by Beyers and Shaw. DOE N89-29228# California Univ., Berkeley. Lawrence Berkeley Lab. VERTICAL GRADIENT FREEZE GaAs: GROWTH AND Maria Lucie Galiano May 1989 66 p Prepared in cooperation (DE89-014894; LBL-27271) Avail: NTIS HC A04/MF A01 The influence of silicon contamination prevention methods on the electrical properties of GaAs grown by the Vertical Gradient Freeze (VGF) technique was investigated. The effectiveness, is reported, of these methods for GaAs crystals grown from two different starting materials: n-type with resistivities in the range of 10(-1) to 10(3) omega-cm and semi-insulating (SI) with a resistivity of 10(8) omega-cm. It was found that the impurities in the starting materials, specifically boron, carbon and silicon, have an effect on the ability to control silicon contamination with methods that have been reported previously in the literature. The attainment is reported of Sl crystals using a PBN crucible, a Sl charge and B203 encapsulation. N89-29229# Los Alamos National Lab., NM. DOE E. J. Peterson, L. E. Wangen, K. C. Ott, K. M. Hargis, T. E. Hakonsen, T. W. Whaley, and W. J. Parkinson Jul. 1989 16 p (Contract W-7405-eng-36) (DE89-014391; LA-11613-MS) Avail: NTIS HC A03/MF A01 The Los Alamos National Laboratory, as a national scientific resource, should be a major participant in the development of new technologies and the improvement of existing technologies that will enhance the nation's industrial competitiveness. Because the Laboratory is a national resource the broadest view of technology development and technology transfer must be taken. As the basic research is converted into useable technologies that can be transferred to the industrial sector, it must be recognized that the job remains incomplete when the product engineering phase is accomplished. A technology or product application that industry cannot implement because of health and environmental constraints will not contribute to our industrial competitiveness. Similarly, a sophisticated technology not accompanied by the appropriate expert knowledge base and process control strategies when technology transfer is attempted will be of marginal use to industry. Thus, it is essential for the Laboratory to take a multidimensional approach to technology development and technology transfer to the industrial sector. The superconducting ceramic oxide materials processing effort of the Exploratory Research and Development Center at Los Alamos provides an excellent opportunity to develop strategies that will address these issues. DOE N89-29230# Sandia National Labs., Albuquerque, NM. EFFECTIVE MASSES AND G FACTORS FOR 2-D LIGHT HOLES IN InSb on J. E. Schirber, C. P. Tigges, L. R. Dawson, H. P. Hjalmarson, and I. J. Fritz 1989 7 p Presented at the International Conference Narrow-gap Semiconductors and Related Materials, Gaithersburg, MD, 12 Jun. 1989 (Contract DE-AC04-76DP-00789) (DE89-014899; SAND-89-0324C; CONF-890621-1) Avail: NTIS HC A02/MF A01 The light holes in InSb are characterized using a Shubnikov-de Haas technique by exploiting the Type 2 band offset of an InAs(.15)SB(.85) InSb strained layer superlattice. The data are analyzed to determine the effective masses and g factors as a function of carrier concentration. N89-29231# Ohio State Univ., Columbus. Dept. of Physics. ULTRASONIC ATTENUATION IN HEAVY FERMION SUPERCONDUCTORS DOE Liam Coffey, N. E. Phillips, ed., R. N. Shelton, ed., and W. A. 1989 Harrison, ed. 2 p Presented at the International Conference on Materials and Mechanisms of Superconductivity High-Temperature Superconductors, Stanford, CA, 23-24 Jul. Submitted for publication (Contract DE-FG02-88ER-45347) 1989 (DE89-014937; DOE/ER-45347/13; CONF-890718-7) Avail: NTIS HC A02/MF A01 The large effective electron mass in the heavy fermion superconductors UPt3 and UBe13 can produce peaks and other features in the temperature and magnetic field dependent sound attenuation. N89-29232# DOE Massachusetts Inst. of Tech., Cambridge. Microsystems Research Center. A MANUFACTURING SCHEDULER'S PERSPECTIVE ON X. Bai and S. B. Gershwin Apr. 1989 33 p In this paper, we describe the phenomena in semiconductor fabrication which are important for production scheduling. We focus our attention on collecting and understanding events, and describing related concepts, such as fabrication processes, operation sets, production machines, support machines, accessories, operation workers, support technicians, activities, Larry C. Olsen Dec. 1988 13 P (Grant AF-AFOSR-0034-87; AF Proj. 2917) (AD-A208861; AFOSR-89-0732TR) Avail: NTIS HC A03/MF A01 CSCL 20/12 The objectives of this program were to purchase and install a Metal Organic Chemical Vapor Deposition (MOCVD) system in the Electronic Materials Laboratory at the Tri-Cities University Center of the University of Washington. This system would be used to grow films of 3 to 5 compounds. This reactor will be used to grow layered structures based on Gallium Arsenide, AlxGa1-xAs, InyGa(1-y)As or GaAsxP1-x. Prior to shipping the MOCVD system, Spire personnel grew GaAs films on GaAs substrates with the TUC 500XT reactor. Excellent results were obtained. Films grown on two-inch wafers exhibited a thickness uniformity of better than 2 percent and a doping uniformity better than 4.5 percent. With three-inch wafers, films were characterized by a thickness uniformity of 4 percent and doping uniformity of 8 percent. They also found that the Aluminum Gallium Arsenide composition uniformity was better than 2 percent for AlGaAs films grown on two-inch waters. Finally, the background doping in epitaxial GaAs films grown with the TUC reactor was determined to be less than 1.5x10 to the 14th power/CC. These performance figures represent a significant improvement in GaAs epitaxial film growth. GRA (AD-A208931; TR-12) Avail: NTIS HC A02/MF A01 CSCL 07/2 Zinc thiogallate crystallizes in a tetragonal space group. In this space group zinc and gallium are disordered in the 4(d) sites. Most of the AGa2x4 compounds crystallize with the defect chalcopyrite, space group 14 where the A and Ga ions are ordered and half of the A-sites are vacant. The result of this work indicates that disordering of Zn and Ga ions can occur and result in a structure with higher symmetry. All of these compounds transmit in the far infrared and are potential infrared window materials. GRA N89-29235# EIC, Inc., Norwood, MA. Jianguo Li, Michael M. Carrabba, and R. D. Rauh Jun. 1989 4 p Presented at the Fall Meeting of the Electrochemical Society, Inc., Hollywood, FL, 15-20 Oct. 1989 (Contract N00014-87-C-0408) (AD-A208991; TR-5) Avail: NTIS HC A02/MF A01 CSCL 20/12 Photoelectromechanical etching of (100) n-gallium arsenide along the (011) crystallographic direction produces V-grooves. It was determined that the groove angle and rate of undercutting of the photoresist mask was dependent on electrolyte composition, light intensity and bias potential. Grating structures could be produced in neutral aqueous electrolytes containing KCL, with angles varying from 80 to 120 degrees as the KCL concentration was varied from 0.01M to 4M. The angles could also be controlled with applied bias and with light intensity. The V-grooves are formed due to the exposure of Ga-rich faces, their composition and angle probably depending on the extent of adsorption of Chloride(-). Non-adsorbing electrolytes such as Fluoride(-) and Sulfate(-) generally gave rougher morphologies and/or passivation. GRA Photochemical etching has been demonstrated as a means for generating high resolution patterns in silicon carbide. Both chemical vapor deposition (CVD) and epitaxial (on Si) SiC were used. Liquid electrolytes containing either fluoride or ethylene diamine were found to promote smooth photoanodic dissolution, without passivation. Very low anodic dark currents permitted the highest degree of spatial selectivity in the epitaxial material, although patterned photoetching of CVD-SiC could be achieved under high light intensity. Diffraction gratings were demonstrated by defining the grating structure in photoresist on the electrode surface, then photoetching the spaces exposed to the electrolyte. SiC has considerable significance as a substrate for gratings in the vacuum ultraviolet and X-ray wavelengths due to its high reflectance in these regions. Additionally, it has a high degree of stability against thermal degradation and radiation damage, making it a choice material for high power laser optics. Because of the extreme hardness of SiC, it is difficult to fabricate gratings by ruling. The photoelectrochemical method demonstrated here is a simple one-step technique that should be adaptable to large area CVD epitaxial SiC substrates that are available commercially. GRA N89-29237# Aerospace Corp., El Segundo, CA. Electronics R. J. Krantz, L. W. Aukerman, and T. C. Zeitlow 26 Apr. 1989 26 P (Contract F04701-88-C-0089) (AD-A209064; TR-0089(4925-07)-4; SD-TR-89-34) Avail: NTIS HC A03/MF A01 CSCL 20/12 A rate equation for charge buildup which includes carrier sweep out, geminate recombination, hole/electron trapping, and effects of internal fields is developed. The first moment of the resulting charge distribution is calculated to yield the midgap voltage shift as a function of irradiation time. The initial midgap voltage shift per dose and the maximum midgap voltage shift are derived. The field dependence of these quantities is shown to be a consequence of the field dependence of the hole/electron capture cross sections and geminate recombination escape probability. The results of this formulation show that the E to the 1/2 power decrease in the midgap shift per dose with increasing applied field. The theory is validated by comparison with experimental results obtained on 225 A thermal oxide on p-type silicon test capacitors irradiated under bias at room temperature. GRA N89-29238# Spire Corp., Bedford, MA. SELECTIVE AREA EPITAXY OF GALLIUM ARSENIDE ON SILICON, PHASE 1 Final Report, 15 Jul. 1988 - 14 Jan. 1989 N. H. Karam Feb. 1989 37 p (Contract DAAL03-88-C-0015) (AD-A209079; FR-60112; ARO-26204.1-EL-SBI) Avail: NTIS HC A03/MF A01 CSCL 20/12 The research program was to investigate selective-area epitaxy of Gallium Arsenide-on-Silicon by Metal Organic Chemical Vapor Deposition (MOCVD) as a means of reducing the thermal expansion mismatch effects, hence, improving the deposited film quality, wafer bow, and eliminating film cracking. This has been achieved by MOCVD of GaAs through openings patterned in the silicon dioxide coated wafers. The object of this research program was to develop the technology that will yield device quality GaAs-on-Si and a process applicable for monolithic integration of the high speed and/or optical communication capabilities of GaAs with the sophistication of the Si very large scale integration (VLSI) technology. The feasibility of this approach has been clearly demonstrated in the Phase 1 research effort, in which successful selective deposition of GaAs films on patterned Si wafers was achieved and the deposited films were characterized by a number of techniques. Preliminary results clearly indicate the effectiveness of this approach to eliminate wafer bow, minimize film cracking, and improve the quality of the heteroepitaxial films. A new deposition technique for GaAs-on-Si by Atomic Layer Epitaxy (ALE) has been introduced which has the potential of producing superior quality GaAs-on-Si films. GRA N89-29239# Measurement Concepts Corp., Colts Neck, NJ. DIGITAL REFRACTOMETRY OF PIEZOELECTRIC CRYSTALLINE MEDIA Interim Report No. 1, Aug. 1987 - Oct. 1988 Edward Collett Nov. 1988 25 p (Contract DAAL01-87-C-0727) (AD-A209362; SLCET-TR-87-0727-1) Avail: NTIS HC A03/MF A01 CSCL 20/2 The contractual objectives of this program are as follows: (1) Perform a theoretical analysis of the measurement of piezoelectric crystals using Dual-Beam Digital Refractometry, (2) Set up the laboratory configuration to determine the refractive indices of piezoelectric crystals using a HeNe Laser source, (3) Determine the refractive indices of various piezoelectric crystals, (4) Expand the measurements to the ultraviolet and infrared regions, and (5) Analyze the requirements for applying Dual-Beam Digital Refractometry to the millimeter and the microwave regions. Contract objective 1 has been completed and is now being written up as a publication. Contract objective 2 was completed by the end of August, 1988. Measurements are now being performed on various samples and the first results will be submitted by the end of February, 1989. Contract objectives 3, 4, and 5 will be completed at the end of the contract, February, 1990. GRA (AD-A209376; MTL-TR-89-10) Avail: NTIS HC A05/MF A01 CSCL 20/2 The series of compositions La(2-X)BaXNiO4 (0 less than or = x less than or = 1.0) was prepared by standard ceramic techniques. All members of the system crystalized with the tetragonal K2NiF4 structure. The ratio of lattice parameters, c/a, reached a maximum in the range x = 0.5 to 0.6; c increased up to this point while a decreased, and this trend reversed after the weak maximum was reached. Increase in c/a is attributed to Jahn-Teller distortion due to octahedral site low-spin Ni(3+) ions. Magnetic susceptibilities measured in the temperature range 6 to 300 K and room temperature resistivity measurements showed that with addition of any barium into the system, a significant change was seen in both magnetic and electrical properties. An anomaly in the magnetic susceptibility was seen at 110 K in La2NIO4. This anomaly disappeared and magnetic susceptibility dropped by a factor of at least one-third with addition of barium. With further increases in barium, the susceptibility value did not differ significantly in all Ba-substituted compounds. Room temperature resistivity dropped from 0.14 Ohm-cm for La2NiO4 to 0.05 Ohm-cm for La(1.8)Ba(.2)NiO4 and decreased only slightly thereafter with increasing barium. Semiconducting behavior was observed for all the compounds. Oxygen stoichiometry is suspected to play a critical role in explaining these behaviors. GRA N89-29241# California Univ., Los Angeles. Dept. of Chemistry and Biochemistry. A STUDY OF THERMODYNAMIC PHASE STABILITY OF INTERMETALLIC THIN FILMS OF Pt2Ga, PtGa AND PtGa2 ON GALLIUM ARSENIDE Technical Report, 1988 - 1989 Young K. Kim, David K. Shuh, R. Stanley Williams, Larry P. Sadwick, and Kang L. Wang 1 Jul. 1989 9 p Submitted for publication (Contract N00014-87-K-0014) (AD-A209698; TR-20) Avail: NTIS HC A02/MF A01 CSCL 09/1 Epitaxial thin films of three different Pt-Ga intermetallic compounds have been grown on gallium arsenide by molecular beam epitaxy (MBE). The resultant films have been annealed at various temperatures and then examined using X-ray two-theta diffraction. Both PtGa2 and PtGa thin films are chemically stable on GaAs under 1 atmosphere of N2 up to 450 C and 600 C, respectively. Thin films of Pt2Ga react with GaAs at temperatures as low as 200 C to form phases with higher Gallium concentration. GRA N89-29242# Center. California Univ., Los Angeles. Solid State Science A BOLT-ON DEPOSITION SOURCE FOR David K. Shuh, Young K. Kim, and R. Stanley Williams 1 Jul. (AD-A209699; TR-19) Avail: NTIS HC A02/MF A01 CSCL 09/1 An eight-inch ConFlat flange assembly with both an electron-beam evaporator and a Knudsen cell has been constructed to deposit intermetallic compounds containing transition and group-3 metals with specific phase composition. Initial depositions of thin films using this design have shown excellent epitaxy with GRA the desired compound stoichiometry. LINESHAPE AND LIFETIME STUDIES OF EXCITON David K. Shuh, R. Stanley Williams, Yusaburo Segawa, Jun-ichi (Contract N00014-87-K-0014) (AD-A209750; TR-21) Avail: NTIS HC A03/MF A01 CSCL 20/12 Photoluminescence studies have been performed on structures, grown by molecular beam epitaxy, with thin films of copper chloride (30 to 1200A) confined between layers of calcium fluoride. Excitons were formed by irradiation of these systems with UV frequencies above the CUCI bandgap, and the spectral and temporal dependences of the recombination radiation were compared to those of a bulk CuCl single crystal. We suggest a kinetic model to explain why the photoluminescence lineshapes of the free excitons in the films were characteristic of a much hotter exciton temperature and the radiative lifetimes were much shorter (less than 40 ps) than those of the bulk CuCl crystal. The photoluminescence from excitons created by hot electrons and holes that combine after above-bandgap excitation in confined CuCl thin films has been investigated. The lifetime of the free-exciton photoluminescence from films with thicknesses of 1200A and less was shorter than the 40-ps resolution of the instrumentation used, whereas the measured lifetime of that in a 1.5 microns-thick CuCl single crystal was 850 ps. This dramatic decrease of the lifetime has been attributed mainly to a decrease of the radiative lifetime of the excitons in the thin films. By examining the lineshape of the free-exciton photoluminescence, an effective temperature of the excitons at the time of decay could be determined. This temperature was increased both by decreasing N89-29244# California Univ., Santa Barbara. Dept. of Physics. EFFECT OF AN ELECTRIC FIELD ON A SPLIT BLOCH BAND Qian Niu 21 Jun. 1989 47 p Submitted for publication (Contract N00014-84-K-0548; NSF DMR-87-03434; NR Proj. 372-160) (AD-A209857; TR-22) Avail: NTIS HC A03/MF A01 CSCL 20/5 The effect of a constant and uniform electric field on a split Bloch band is studied through a tight binding model. The Wannier-Stark ladders of the parent band are modified by a potential in addition to that of the crystal. It is shown how the frequency spectrum behaves as the field strength varies from weak to strong. In the case that the parent band is split into a finite number of sub-bands, there exists a set of subspaces to which the states return periodically in time, and that the constituent states of each subspace are localized around a given unit cell. A theoretical framework is developed which naturally exploits the symmetries of the system, and which allows for easy and clean numerical calculations. GRA N89-29245# California Univ., Los Angeles. Dept. of Chemistry and Biochemistry. INITIAL STAGES OF METAL/SEMICONDUCTOR INTERFACE FORMATION: Au AND AgON SI(111) Technical Report, 1988 1989 R. Stanley Williams, Richard S. Daley, Judy H. Huang, and Robert M. Charatan 20 Jun. 1989 17 p (Contract N00014-87-K-0014) (AD-A209490; TR-18) Avail: NTIS HC A03/MF A01 CSCL 20/12 The atomic structure formed by monolayer coverages of Au and Ag on the Si(111) surface was studied using primarily the technique of Impact-Collision lon Scattering Spectroscopy (ICISS). For the case of Au films annealed at 700 C, three different types of LEED patterns are formed depending on the fractional monolayer coverage: 5x1, sq. root of 3 x sq. root of 3, and 6x6. The ICISS data reveal that all the three surfaces are structurally similar: the Au atoms reside above the Si(111) plane, most likely in threefold-hollow sites, and the different surfaces appear to be characterized by rows (5x1) or a honeycomb network (sq. root of 3 x sq. root of 3 and 6x6). In contrast, the Ag films deposited at elevated substrate temperature (480 C) display only a sq. root of 3 x sq. root of 3 LEED pattern for coverages ranging from 0.25 to 35 monolayers. A trimer model appears to be more consistent with the low coverage Ag ICISS data rather than a honeycomb arrangement of the Ag atoms. N89-29246# Pittsburgh Univ., PA. School of Engineering. Scott G. Young and Joseph H. Magill 4 May 1989 GRA 17 P (AD-A207719; ONR-11) Avail: NTIS HC A02/MF A01 CSCL 20/5 In situ solid state variable temperature NMR measurements have been made on Poly(bis(trifluoroethoxy)phosphazene above and below the first order thermotropic transition, T(1). A single mobile ordered 2D phase exists above T(1). Below T(1) and at room temperature there is a 3D phase in agreement with other physical property measurements. The OCH2CF3 side chains exhibit similar mobility on either side of the 2D in equilibrium with 3D transition. The activation energies associated with the CH2 and CF3 side groups are E sub CH2 about 17.3 kJ/mole and E sub CF3 about 13.7 kJ/mole. The spin lattice relaxation measurements for these same groups are 1.75s. and 3.55s. respectively. The crystallinity ascertained from solid state NMR results is strongly N89-29247# Aerospace Corp., El Segundo, CA. Chemistry and CHEMICAL EFFECTS OF Ne(+) BOMBARDMENT ON THE Jeffrey R. Lince, Thomas B. Stewart, Malina M. Hills, Paul D. (Contracts F04701-85-C-0086; DE-AC02-76CH-00016) The effect of 1-keV Neon cation bombardment on the clean Molybdenum disulfide (0001) - 1 x 1 surface with fluences between 4 x 10 to the 14th power Ne(+)/sq cm was studied using high-resolution photoelectron spectroscopy excited with synchrotron radiation. Spectra of the Mo-3d and S-2p core levels were measured with photon energies that ensured that the kinetic energy of their photoelectrons was the same, resulting in the same depth being probed for both core levels. For lower fluences, S vacancy defect formation occurs in the MoS2 lattice, with the concurrent formation of a small amount (less than 10 percent) of dispersed elemental molybdenum Mo(0). For fluences greater than approx. 1 x 10 to the 16th power Ne(+)/sq cm, the Mo(0) is the predominant species in the surface region, while the remaining species consists of amorphous MoS(2-x) and polysulfide species. Valence band spectra taken with photon energies of 152 eV and 225 eV were consistent with the core level results. The movement of the valence band maximum toward the Fermi level indicated the formation of a metallic surface region. A qualitative depth distribution of the chemical species present after Ne(+) bombardment was determined. GRA QUANTITATIVE ANALYSIS OF LASER INTERFEROMETER WAVEFORMS OBTAINED DURING OXYGEN REACTIVE-ION ETCHING OF THIN POLYMER FILMS 12 May 1989 B. C. Dems, F. Rodriguez, and P. D. Krasicky 23 p Presented at the ACS Division of Polymeric Materials, Science and Engineering Symposium on Polymers in Microlithography, Dallas, TX, 9-14 Apr. 1989 (Contract N00014-85-K-0474) (AD-A207836; TR-14) Avail: NTIS HC A03/MF A01 CSCL 20/12 Continuous laser interferometry, especially of inorganic materials, during reactive ion etching often has been used as an end-point detection method. However, the detailed patterns obtained during etching of thin organic polymer films have not been fully exploited. The sinusoidal oscillations in reflected light intensity often exhibit almost uniform amplitudes. In addition to variations in the rate of etching with time or depth, a rigorous analysis of the waveform yields an in situ measure of the refractive index of the film. A reduction factor for the medium/polymer interface Fresnel coefficient is used to account for the diffuseness arising from roughening of the film. Ion bombardment causes the roughening and necessitates the correction which is not usually the case when interferometry is used in solvent dissolution studies. The analysis, an iterative procedure for its use, and the application to oxygen/RIE of several polymers will be described. GRA N89-29249# Utah Univ., Salt Lake City. Dept. of Physics. (AD-A207925; AFOSR-89-0604TR) Avail: NTIS HC A03/MF Studies were made of fluxon dynamics, instabilities, and noise |