1998 MRS Fall Meeting & Exhibit

Chairs

Francis Di Salvo, Cornell Univ 
Robert Haushalter, Symyx Technologies
Tom Lee, Symyx Technologies
Nate Lewis, California Inst of Technology
Ralph Nielsen, Symyx Technologies
Patricia Watson, DuPont

Symposium Support 

• DuPont, Central Research & Development
• Symyx Technologies 

* Invited paper

SESSION CC1: MATERIALS DISCOVERY AND DEVICE OPTIMIZATION 
Chair: Robert C. Haushalter 
Monday Morning, November 30, 1998 
Fairfax A/B (S)

8:30 AM *CC1.1 SYNTHESIS AND CHARACTERIZATION OF METAL OXIDE THIN FILM AND DEVICE LIBRARIES. I. Takeuchi , H. Chang, C. Gao, J. Wang, Y.K. Yoo, X.-D. Sun, P.G. Schultz, and X.-D. Xiang, Materials Sciences Division, Lawrence Berkeley National Laboratories, Berkeley, CA; R P. Sharma and T. Venkatesan, Department of Physics, University of Maryland, College Park, MD. In order to address materials issues of increasingly complex functional metal oxides, we have developed comprehensive combinatorial synthesis and evaluation methods targeting a variety of electronic thin film applications. Thousands of different precursor combinations are created on individual chips by successive deposition of precursors through in-situ metal masks and/or lithographic lift-off steps with rapid turn-around. Our film deposition methods include a high-vacuum multi-target pulsed laser deposition system equipped with automated high-precision in-situ shutters and RF sputtering. In order to efficiently survey a diverse variation of compositions in a given library, various masking schemes are used to design high density libraries (e.g. 1024 samples in 1 cm²). The in-situ shutters are also used for creating controlled gradient composition samples for optimizing the composition of lead compounds selected from the libraries. Following the depositions, samples undergo various annealing processes for interdiffusion of precursors and crystal growth of the materials. Rutherford backscattering is used to confirm proper interdiffusion and uniformity of the composition. X-ray diffraction reveals that predominantly single phase epitaxial films with good crystallinity can be obtained in the libraries. Libraries are then screened for desired physical properties using various scanning measurement techniques including scanning evanescent microwave microscopy. From phosphors libraries, we have discovered several novel materials including a blue emitting composite Gd₃Ga₅O_12/SiO_x. From ferroelectric/dielectric libraries, we have found that doping Ba_xSr_1-xTiO_3-CONJUGATED POLYMERS. Yukiko Muramatsu , Tsukasa Maruyama, Takakazu Yamamoto, Tokyo Institute of Technology, Research Laboratory of Resources Utilization, CREST, Japan Science and Technology Corporation, Yokohama, JAPAN; Kazuhiko Hara, Hiroo Munekata, Tokyo Institute of Technology, Imaging Science and Engineering Laboratory, Yokohama, JAPAN; Takuya Hashimoto, Tokyo Univ., Dept of Arts and Science, Tokyo, JAPAN; Mamoru Yoshimoto, Hideomi Koinuma, Tokyo Institute of Technology, Ceramics Materials and Structures Laboratory, CREST, Japan Science and Technology Corporation, Yokohama, JAPAN. 

p-Conjugated and electrically conductuind polymers have recieved much attention due to their interesting fundamental properties as well as their applicability to the present and possible future. The p-conjugated polymers are essentially regarded as one-dimensional conductors, and alignment of them have also been investigated on many substrates due to bring out their exellent properties. In this research, we concerned with survey of a superior combination for photoluminescence material of p-conjugated polymers with combinatorial method. Materials, the p-conjugated polymers have been prepared by organometallic techniques using nickel or palladium complexes. Combinatorial vacuum evaporation of p-conjugated polymers on ITO coated glass substrate are carried out using binary or quaterly masks to define the areas of each layer. Typically deposition conducted under the conditions of 2  5 x 10^-6 Torr and room temperature. Obtained layered films exhibited bright visible photoluminescence of blue  yellowish green colors photoluminescence. Some of double or triple layered films showed stronger fluorescence compared with single layererd ones. These results demonstrated that the interaction between stacked layeres influence to photoluminescense spectrum. 

10:15 AM *CC1.4 
COMBINATORIAL SYNTHESIS OF ARTIFICIALLY DESIGNED LATTICES AND DEVICES. Hideomi Koinuma ^1,2, Takeshi Ohnishi¹, Christian Satuter¹, Masashi Kawasaki³, Ryuichiro Maruyama¹, Hemant Aiyer¹; ¹Ceramics Materials & Structures Laboratory, Tokyo Institute of Technology, Yokohama, JAPAN; ²CREST-JST; ³Department of Innovative and Engineered Materials, Tokyo Institute of Technology. 

Material structure and properties are dependent; not only on the composition but also on such preparation parameters as temperature, pressure, activation energy source, and reaction duration. We are especially interested in the development of new systems to use these parameters as variables for combinatorial synthesis of atomically controlled materials such as new crystal lattices, superlattices, and quantum wires and dots. This technology can be extended to the fabrication of combinatorial junction and device libraries. As-grown fixation of each thin film layer with its area, thickness, and lattices defined by masks, deposition time, and ambient conditions, respectively, is the basis for this technology. Two such methods are presented, together with their preliminary results. 
1) Combinatorial laser MBE Laser MBE is a system which we have been verifying its usefulness for atomic or molecular layer epitaxy of oxides by in situ observation of RHEED intensity oscillation. By installing electron beam scanning and masking mechanisms, combinatorial superlattice libraries of perovskite oxides could be synthesized. 
2) Combinatorial plasma CVD 
A conventional plasma CVD apparatus was made compatible with combinatorial synthesis by introducing one-directional mask sliding and 90 degree substrate rotation tools. Initial growth process of a-Si:H and optimization of a-Si:H/a-SiN:H bilayer for the field effect solar cell have been investigated as functions of substrate materials and surface treatment, deposition temperature, source gas composition, and film thickness. 

10:45 AM CC1.5 
COMBINATORIAL METHODS FOR OPTIMIZATION OF MATERIALS SELECTION AND DEVICE PARAMETERS IN OLEDs. Hans-Werner Schmidt , Christoph Schmitz, Mukundan Thelakkat, Makromolekulare Chemie I, Universitat Bayreuth, GERMANY. 

Electroluminescence displays based on organic materials are presently in a stage of materials screening and optimization of device structure and performance. The concept of combinatorial methods has been successfully applied to various fields such as peptide-chemistry and development and optimization of catalysts for polyolefines. Recently this method has also been applied in the synthesis of new inorganic photoluminescense- [1] and semiconducting materials [2]. In this contribution we present the applicability of this method for the optimization of different parameters in OLEDs such as layer-thickness, the simultaneous variation of layer thickness and device configuration and composition of different layers in multi-layer devices. To achieve these goals we developed an apparatus consisting of a movable mask sliding carriage and a turnable substrate holder. This set-up is placed into a vacuum deposition chamber and various combinations of device configurations have been realized. To analyze the specific data and the libraries current-voltage-electroluminescence measurements were carried out. In this way the correlated layer thicknesses of a typical device: ITO/TPD/Alq3/Al can be optimized in one experiment. Experiments were carried out with several newly developed hole transporting materials. In order to screen different materials for their potential application in OLEDs, binary mask techniques were utilized. With these techniques it is possible to create well defined areas of different materials and compositions. Results will be presented on various combinations of hole transporting, emitting and hole blocking/electron transporting materials. 

11:00 AM CC1.6 
COMBINATORIAL SUPERLATTICE SYNTHESIS BY USING LASER MBE COMBINED WITH SCANNING RHEED AND MASK SYSTEM. T. Ohnishi ¹, H. Koinuma^1,2, C. Stauter², M. Lippmaa¹, S. Ohashi¹, M. Kawasaki³; ¹Ceramics Materials and Structures Lab.,Tokyo Inst. of Tech., Yokohama, JAPAN; ²CREST-JST; ³Dept. of Innovative and Engineering Materials, Tokyo Inst. of Tech., Yokohama, JAPAN. 

Recently, combinatorial approach in material science has attracted much attention, since its rapid synthesis of large number of libraries can accelerate the discovery and optimization of useful ceramics materials. However, its application has primarily been focused on library synthesis by using sintering for reaction and composition such as stoichiometry and doping element as a variable parameter. We report here the epitaxial growth of heterostructures combined with combinatorial synthesis of thin film libraries. Sequential deposition of atomically regulated layers on areas defined by masks allowed us to form a series of superlattices with different characteristics (i.e. composition, periodicity and layer thickness) on a same substrate. Laser molecular beam epitaxy (laser MBE) was employed as a deposition technique to use reflection high energy electron diffraction (RHEED) for in-situ monitoring of surface reaction. In order to monitor the lattice structure of growing films as well as to control the film thickness at many regions simultaneously during the deposition process, high energy electron beam was scanned on the regions defined by masks. By this combinatorial laser MBE, we have fabricated a few perovskite superlattices. Results are presented on the precision of structural control and discussed in relation to the properties of superlattices. 

11:15 AM CC1.7 
COMBINATORIAL MICROLAB INVESTIGATION OF COPPER-CORROSION MECHANISMS. J.C. Barbour , J.W. Braithwaite, J.P. Sullivan, W.G. Breiland, N. Missert, and J.S. Nelson, Sandia National Laboratories, Albuquerque, NM. 

Combinatorial analysis was combined with microscopic experimentation (the Combinatorial Microlab) in order to determine mechanisms for copper corrosion. Corrosion studies are inherently difficult because of complex interactions between materials and environment, forming a multidimensional phase space of corrosion variables. The Combinatorial Microlab was specifically developed to address the mechanism of Cu sulfidation, which is an important reliability issue for electronic components. This approach differs from convention by focusing on microscopic length scales, the relevant scale for corrosion. During accelerated aging, copper is exposed to a variety of corrosive environments containing sulfidizing species that cause corrosion. A matrix experiment was done to determine independent and synergistic effects of initial Cu oxide thickness and point defect density. The Cu₂O was controlled by oxidizing Cu in an electron cyclotron resonance (ECR) O₂plasma, and the point defect density was modified by Cu ion irradiation. The matrix was exposed to 600 ppb H₂S in 75relative humidity air atmosphere. This combination revealed the importance of oxide quality in passivating Cu and prevention of the sulfidizing reaction. A native oxide and a defect-laden ECR oxide both react at 20C to form a thick Cu₂S layer after exposure to H₂S, while different thicknesses of as-grown ECR oxide stop the formation of Cu₂S. The ECR oxide growth rate will be presented as a function of temperature and plasma-ion energy. Combinatorial experiments (arrays of microlabs) are also being used to characterize the direct and synergistic effects of the following variables: Cu morphology and metallurgy (alloying), environment (humidity, temperature, sulfide concentration), and functionality (e.g., electric-current conduction). Novel diagnostics will include: in-situ electrical conductivity and light scattering to monitor real-time evolution of corrosion reactions. Experimental results will be compared to models of the Cu corrosion process. 

11:30 AM CC1.8 
AUTOMATED COMBINATORIAL ZEOLITE SYNTHESIS. David Gardner , Nicole Hilbrandt, Phillip Fanwick and Thomas Bein, Department of Chemistry, Purdue University, West Lafayette, IN. 

The application of combinatorial approaches to the hydrothermal synthesis of zeolites depends on the development of methodologies for rapid synthesis under harsh conditions and for appropriate structural screening protocols. In order to achieve this goal, a new methodology based on automatic dispensing of reagents into autoclave blocks (ìmulticlavesî) was developed. We demonstrate that a complete experiment (from mixing of reagents to x-ray structural analysis) can be performed without manipulation of any of the individual samples. A costum-built robot allows us to dispense and mix multiple liquids simultaneously into specially designed Teflon multiclaves. The multiclaves are then transferred to steel chambers that allow us to heat the reaction mixtures to at least 170C. The samples can be repeatedly washed and then completely transferred onto sample holders using centrifugation. The products can then be analyzed while on the sample holder using transmission x-ray diffraction. 
Several synthetic examples illustrating this methodology will be discussed, including a scan of crystallization fields in the sodium aluminosilicate parameter space. For example, using colloidal silica, a sodium aluminate solution, and a sodium hydroxide solution, zeolites SOD, FAU and LTA were synthesized in 24 h at 110C. 

11:45 AM CC1.9 
SYNTHESIS OF MICROPOROUS ALUMINOPHOSPHATE PHASES USING COMBINATORIAL METHODS. Kwangwook Choi , David Gardner and Thomas Bein, Department of Chemistry, Purdue University, West Lafayette, IN. 

The optimization of existing hydrothermal synthesis procedures for microporous materials and the discovery of new phases depend on effective processing and structural screening methodologies. We have developed a combinatorial approach based on reagent injection into multireactor blocks (ìmulticlavesî) and parallel processing followed by automated x-ray diffraction analysis. In this contribution, we present the synthesis of several aluminophosphate phases applying combinatorial strategies. In particular, it was of interest to study the influence of organometallic and organic structure directing agents (ìtemplatesî) on the resulting aluminophosphate phases. For example, aluminum and phosphate sources were mixed with water followed by a solution of the template, including ferrocenium and cobalticinium salts and quinuclidine, to form the starting gel. In a representative synthesis, the molar ratios of Al2O3/P2O5/water/templates in the starting gels were 1/1/160/0.5-1. The gels were shaken overnight, followed by hydrothermal synthesis. The resulting phases include AWW with both ferrocenium and cobalticinium templates, and AST with quinuclidine. Crystallization fields of these and other phases as well as the effects of template structure, solvents, framework precursors, and temperature on the resulting aluminophosphate phases will be discussed. 

SESSION CC2: HIGH-THROUGHPUT SCREENING AND NOVEL SENSORS 
Chair: Tom Lee 
Monday Afternoon, November 30, 1998 
Fairfax A/B (S)

1:30 PM *CC2.1 
USING COMBINATORIAL APPROACHES IN SENSORS. David R. Walt , Todd Dickinson, Karri Michael, Keith Albert, Jane Ferguson, Frank Steemers, Tufts University, Chemistry Department, Medford, MA. 

Optical sensors have been designed that draw heavily from the field of combinatorial chemistry. In one approach, receptor libraries with built-in optical transduction have been created that can be screened for analyte binding. The resulting receptors can then be used in sensors and sensor arrays. Another approach takes the combinatorial paradigm and applies it to the design of a sensor system based on principles of the olfactory system. The resulting sensor array employs highly cross-reactive sensors combined with computational networks to create a broad-band detection system. In another format, encoded sensor libraries are used to generate high-density arrays. Finally, a combinatorial approach has been taken to identify polymers with desired sensing properties. Screening of these polymers is accomplished by evaluating their responses to target analytes when employed in a sensor format. 

2:00 PM CC2.2 
COLLOIDAL ARRAYS: NOVEL DEVICES AND TAGGING METHODS IN COMBINATORIAL CHEMISTRY. Matt Trau , Dept of Chemistry, University of Queensland, Brisbane, AUSTRALIA. 

The advent of combinatorial chemistry has brought about many challenges to the materials scientist. The development of inexpensive rapid-throughput assays has taken on a priority. We will describe novel field-induced colloidal assembly procedures which allow rapid and inexpensive construction of microscopically arrayed combinatorial chemistry libraries. The technique utilizes solid phase colloidal resins as the primary elements in the array. The original technique was first reported by Trau, Saville and Aksay in 1996.* The library arrays currently produced typically contain one million or more easily addressable elements, assembled in a massively paralleled fashion. A novel technique for rapidly encoding and decoding colloidal particles (individual elements) within the array will also be discussed. 

2:15 PM *CC2.3 
A COMBINATORIAL APPROACH TO CHEMICAL SENSING USING CARBON BLACK-POLYMER COMPOSITE CHEMIRESISTORS. Adam J. Matzger , Carolyn Lawrence, Robert H. Grubbs, Nathan S. Lewis, California Institute of Technology, Division of Chemistry and Chemical Engineering, Pasadena, CA. 

A vapor sensor has been constructed of an array of carbon black-polymer composites. Each composite detector gives a unique differential resistance response upon exposure to vapor analytes due to the varying sorption properties of the polymer insulator. Fabricating a sensor array with a set of copolymers, of varying monomer ratios, has shown that responses between the different composites display a relationship which is not simply related to the fraction of each monomer. This suggests that many uniquely responding detectors can be combinatorially constructed from a minimal starting library of monomers. An alternate approach to generating sensor diversity takes advantage of the effect of added plasticizers on the sorption properties of polymers. This strategy has allowed for the construction of a library of sensors utilizing commercial polymers and additives which have provided improved resolution in organic vapor sensing when compared to the pure polymers. 

3:15 PM *CC2.4 
COMBINATORIAL CHEMISTRY: NEW TECHNOLOGIES FOR DRUG DISCOVERY. Mark A. Gallop , Affymax Research Institute, Palo Alto, CA. 

Combinatorial chemistry encompasses a variety of technologies and synthetic strategies in which potentially large numbers of products may be prepared simultaneously by combining a set or sets of chemical building blocks (or monomers) in just a few synthetic steps. The term is often used to describe the preparation of many compounds as discrete products of chemical reactions run in parallel, as well as the preparation of compound mixtures through combination of multiple reacting partners in the same reaction vessel. The earliest combinatorial experiments dating from the mid-1980's used peptide chemistry to study the molecular recognition properties of antibodies. Over the past five years pharmaceutical companies have enthusiastically embraced combinatorial synthesis for its ability to produce large collections (or libraries) of molecules to augment their existing sources of molecular diversity, and to fully exploit their capacity to capture millions of biological assay data points annually using high-throughput robotic screening instrumentation. 
 The rapid, recent advances made in combinatorial chemistry are intimately linked with a surge of interest in solid-phase organic synthesis. Although not obligatory in the practice of combinatorial synthesis, the use of solid-phase methods offers some compelling advantages when attempting multi-step combinatorial reaction sequences, and additionally has led the development of a number of clever approaches for manipulation and structural characterization of individual members of complex library mixtures. 
This talk will introduce some of the important strategies and techniques of combinatorial synthesis and feature application of these tools to the discovery of biologically active compounds from combinatorial libraries. 

3:45 PM CC2.5 
DEVELOPMENT OF A MULTI-ANALYTE SENSOR ARRAY COMPOSED OF RECEPTOR-TAGGED POLYMERIC MICROSPHERES LOCALIZED IN MICROMACHINED CAVITIES. Steve M. Savoy,^a John J. Lavigne,^a J. Bridget Clevenger,^a J. SeungJin Yoo,^bJohn T. McDevitt ,^a Eric V. Anslyn,^a Jason B. Shear,^a Dean P. Neikirk,^b a Department of Chemistry and Biochemistry and ^bDepartment of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX. 

The development of a sensor array composed of individually addressable polystyrene-polyethylene glycol composite microspheres has been demonstrated. The microspheres are selectively arranged in micromachined cavities localized on silicon wafers which have the rear face terminated with a Si₃N₄-SiO₂-Si₃N₄ transparent membrane. The membrane acts as a window and enables studies of the optical properties of sensing elements upon their exposure to analyte species. Sensing occurs via colorimetric changes to receptor molecules which are covalently attached to amine termination sites on the polymeric microspheres. The unique combination of carefully chosen ''reporter'' molecules with water permeable microspheres provides a means for the simultaneous detection of a variety of analytes. The fabrication of the sensor structure and the colorimetric responses measured using a chargecoupled device (CCD) for pH, Ca⁺², Ce⁺³, and sugar are reported. In addition, the response time of selected indicatorbound microsphere elements is described. 

4:00 PM *CC2.6 
SYCHROTRON X-RAY MICROBEAM DIAGNOSTICS OF COMBINATORIAL SYNTHESIS. E.D. Issacs, M.A. Marcus, Bell Laboratories, Murray Hill, NJ; M. Kao, G.S. Cargill III, Dept of Chemical Engineering, Columbia University, New York, NY; G. Aeppli , NEC Research Inst., Princeton, NJ; X.-D. Xiang, X. Sun, P. Schultz, Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, CA; R. Haushalter, Symyx Technologies, Sunnyvale, CA. 

X-ray microbeam techniques (spot size  3 x 20 m²) have been applied to characterize the composition and structure of rare earth activated Gd(la,Sr)AlO₃ phosphor thin films grown by combinatorial synthesis. Using x-ray fluorescence, x-ray diffraction and near-edge x-ray absorption spectroscopy we measure the composition, crystallographic structure and valence state of the rare earth activator atom EU. These measurements represent the first direct application of x-ray techniques to solid-state materials prepared by combinatorial synthesis and demonstrate the power of x-ray microbeam analysis to non-destructively characterize as-grown combinatorial libraries. 

4:30 PM CC2.7 
ENZYMATICALLY-GENERATED POLYPHENOLS AS ARRAY-BASED SENSING MATERIALS FOR METALS. Xiaoqiu Wu ^1,*, Jungbae Kim^1,*, Jonathan Dordick^1,2 1Department of Chemical and Biochemical Engineering, and Center for Biocatalysis and Bioprocessing University of Iowa, Iowa City, IA; ²Division of Medicinal and Natural Products Chemistry, College of Pharmacy University of Iowa, Iowa City, IA. 

Phenolic polymers containing fluorescent reporter molecules were prepared via soybean hull peroxidase (SBP) catalysis, and used as metal-based sensor components. Specifically, we generated a variety of phenolic homopolymers containing p-cresol, p-phenylphenol, or p-methoxyphenol and containing one of two fluorophores, fluorescein and calcein. The fluorescence of the resulting polyphenol were dependent on the presence of metal ions including Cu²⁺, Fe²⁺, Zn²⁺, Mn²⁺, and Fe³⁺. The fluorescence response was dependent upon both the metal ion and the phenolic monomer used in polyphenol synthesis, indicating that significant control over the selectivity and sensitivity of metal sensing can be achieved by varying the components that comprise the phenolic polymer. In some cases, metal ion concentrations as low as 10 M can be analyzed. The broad reactivity of SBP towards phenolic monomers enables the use of a wide array of structures and chemistries that can assist in metal ion detection. Similar combinatorial approaches to enzyme-catalyzed polyphenol synthesis are currently under investigation and are expected to provide a large and diverse array of sensing materials. 

4:45 PM CC2.8 
CHEMICALLY AND SPATIALLY RESOLVED IDENTIFICATION OF MOLECULES DESORBED FROM FUNCTIONALIZED POLYMERIC MICROSPHERES AND SILICON MICROVIAL ARRAYS: A TOF-SIMS IMAGING INVESTIGATION. Robert M. Braun , Nicholas Winograd, Penn State Univ, Dept of Chemistry, University Park, PA. 

Combinatorial synthesis offers enormous potential in the drug discovery arena by enabling molecular libraries to be created with diversities in excess of 1e6 members. Moreover, the solid phase applications of this powerful synthetic technique have generated a great deal of excitement within the pharmaceutical and materials science industries. The use of polymeric micro-spheres and processed Si wafers (microvials) demands the incorporation of new bioassay and chemical processing protocols in order to expedite the discovery of unique chemical structures. Here we show that it is possible to identify the molecules desorbed from individual micro-spheres or from Si microvials (ca. 40 micron), as well as to characterize large arrays within a single ToF-SIMS image. This advance far exceeds the assaying speed of competing mass spectral techniques such as MALDI and electrospray ionization. 

SESSION CC3/FF4: JOINT SESSION: 
COMBINATORIAL METHODS IN CATALYSIS I 
Chairs: Ralph Nielsen and Patricia Watson 
Tuesday Morning, December 1, 1998 
Hampton A/B (S)

8:30 AM *CC3.1/FF4.1 
SYNTHESIS AND SCREENING STRATEGIES FOR THE DISCOVERY OF NEW OLEFIN POLYMERIZATION CATALYSTS. Thomas Boussie, Timothy Powers, Howard Turner, Vince Murphy . Symyx Technologies, Santa Clara CA.

Abstract not available.