bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and Physical Properties of Self-Orienting Head-To-Tail Polythiophenes.
Authors: McCullough Richard D. , Williams Shawn P. , Jayaraman Manikandan , Reddinger Jerry , Miller Lynnette , Tristram-Nagle Stephanie
Published: March 2011

Designed synthesis and architectural assembly of head-to-tail polythiophene derivatives provide the ability to control π orbital topology and orbital interactions in conjugated polymers. The preparation of polythiophene derivatives with essentially 100% head-to tail (HT) couplings leads to defect free polythiophenes. These new HT polythiophenes can undergo macromolecular self-assembly to give self-oriented conducting polymers. Study of these materials has led to new insights on structure-property relationships in this class of Materials. In addition, these results show that the molecular orbital overlap, the band dimensionality, and the solid state structure are quite sensitive to the nature of the side chains attached to the polymer's backbone. In addition, we have now synthesized the first heteroatom functionalized HT polythiophenes. These polythiophene derivatives can bind cations, and ion recognition can be used to tune conjugation lengths and properties in polythiophenes. Also presented are a class of random HT coupled 3-alkylthiophenes whose optical and electrochemical properties and possibly electronic properties can be altered by recipe.
A New Dithiophene Fused p-Phenylene Vinylene Conducting Polymer. Synthesis and Study
Authors: Pomerantz Martin , Wang Jiping , Seong Seeyearl , Starkey Kyle P. , Nguyen Long , Marynick Dennis S.
Published: March 2011

A new conducting polymer, poly (benzo[1,2-b:4,5-b′]dithiophene-4,8-diyl vinylene) (1), has been prepared by pyrolysis of a precursor polymer 2, which, in turn, was prepared by a multistep synthetic sequence (Scheme 1). The polymer has a UV-vis spectral maximum at 501 nm (2.48 eV), band-gap (band edge) of 1.92 eV and with FeC?3 doping a conductivity of 15 S cm1. Quantum Mechanical calculations using PRDDO, ab-initio and modified extended Hiickel Methodology on the Monomers, trimers and polymers, both aromatic and quinoid, provided structures and an absorption maximum band-gap which is consistent with either a planar aromatic polymer or a polymer which has both aromatic and quinoid units.
Soluble Conducting Polythiophenes for Charge Dissipation in Electron Beam Lithography
Authors: Huang Wu-Song
Published: March 2011

In electron beam lithography, charging on photoresist usually causes image distortion and placement error. To dissipate the charge, a conductive polymeric layer can be introduced either over or under the photoresist coating. In this paper, we will discuss the approach of using toluene and xylene soluble polyalkylthiophcne in combination with photoacid generator as a discharge underlayer or interlayer beneath photoresist to dissipate the accumulated charge during li-bcam exposure. We will also discuss the use of water soluble acid or ammonium salt form of poly 3- (cthanesulfonate) thiophene as discharge. toplayer. During the resist image developing process, the toplayer will be removed by aqueous base. Therefore, it is advantageous to use discharge toplayer due to its simplicity. In this study, the salt and acid form of poly 3- (ethanesulfonate) thiophene was synthesized through chemical polymerization of the corresponding methanesulfonate ester. It exhibits the same properties as that of electrochemically synthesized polymer reported in the literature.
Characterization And Photoconductive Properties Of Highly Oriented Thin Films Of Oxotitanium Phthalocyanine Prepared By Vacuum Deposition Technique
Authors: Yonehara Hisatomo , Pac Chyongjin
Published: March 2011

Thin films of oxotitanium phthalocyanine were grown on optical flat PYREX glass substrates at 0.05 – 1.5 nm/s under 2×l0-4Pa. The films were analyzed by X-ray diffraction patterns (XRD) and polarized absorption spectra to reveal a preferred molecular orientation in the films evaporated at 0.05 nm/s, but amorphous nature of the films prepared at higher deposition rates. All the films were changed in the crystallinity to α-form Microcrystals upon exposure to vapor of methylene chloride or tetrahydrofuran. XRD analysis of the vapor-treated films at 0.05 nm/s showed only an intense peak at 2θ = 7.50°, demonstrating that the (010) face of the α-form crystal is highly oriented perpendicularly to the substrate surface. The Molecular orientation was again demonstrated by polarized absorption spectra. The photoconductive behavior of the films was found to depend on the deposition rates as well as on the vapor treatment.
Influence of Anisotropic Scattering Along the 2D-Fermi Surface on Transport Properties in an Asymmetric-Donor-Based Molecular Crystal
Authors: Fortune Nathanael A. , Murata K. , Papavassjuou G. C. , Lagouvardos D. J. , Zambounis J. S.
Published: March 2011

We report our results for the temperature dependence of the Hall coefficient and in-plane resistivity for the asymmetric-donor-based quasi-2D Molecular crystal τ- (P-S,S-DMEDT-TTF)2 (AuBr2)1(AuBr2)y (y≈0.75). Using a recent “geometrical representation” of the weak-field 2D Hall conductivity developed by N.P. Ong [Phys. Rev. B 43, 193 (1991)], we model the temperature dependence of these electronic transport properties in terms of the temperature dependence of the scattering path length and its anisotropy along the 2D Fermi surface.
Fermi Surface and Magnetoresistance in an Organic Metal β″ -(BEDT-TTF)2AuBr2
Authors: Uji S. , Aoki H. , Tokumoto M. , Ugawa A. , YakushP K.
Published: March 2011

The Shubnikov-de Haas (SdH) and Magnetoresistance Measurements have been performed in an organic Metal β″ (BEDT-TTF)2AuBr2. Absence of saturation in the magnetoresistance up to 13T suggests that this salt is a compensated Metal. The SdH oscillations are consistently understood by assuming that three cylindrical Fermi surfaces are present. The frequencies of the SdH oscillations corresponding to the Fermi surfaces are determined to be 41.5 T, 139 T, and 181 T for H//b*-axis. An anomalous maximum in the resistance is found at about 9.5 K for H//b*-axis although no anomaly is observed for H//plane.
Synthesis, Layer Assembly, And Fluorescence Dynamics Of Poly (Phenylenevinylene) Oligomer Phosphonates
Authors: Katz H. E. , Shane S. F. , Wilson W. L. , Schilling M. L. , Ungashe S. B.
Published: March 2011

The title oligomers have been incorporated in Zr-based layers on quartz substrates. Absorbance and emission spectra and fluorescence decays have been measured on these films and compared with data from solutions, powders, and PPV. The samples may be divided into those with “liquid-like” behavior and “solid-like” behavior; the latter is characterized by blue-shifted absorbance, red-shifted emission, and more complex decay dynamics than the former. By these criteria, the layers and PPV itself are decidedly “solid-like’.
Light-Emitting Diodes Using Semiconducting Oligothiophenes
Authors: Uchiyama K. , Akimichi H. , Hotta S. , Noge H. , Sakaki H.
Published: March 2011

The light-emitting diodes (LEDs) using semiconducting oligothiophenes, dimethylquater-thiophene (DMQtT, tetramer), dimethylquinquethiophene (DMQqT, pentamer) and dimethyl-sexithiophene (DMSxT, hexamer), have been investigated. These oligomers were deposited on ITO-coated glass in ultra high vacuum and an aluminum electrode was subsequently vacuum-deposited on top of the oligomers. These structures have the diode configuration with Schottky barrier between the oligomers and aluminum.

The LED using DMSxT shows good rectifying feature with the rectifying ratio of 1500 at ±10V.Red-orange emission is clearly observed above 4V bias. In this LED, DMSxT acts not only as an emitting layer but also as a hole transport layer. We have also fabricated and studied alternate layered structures of DMSxT/DMQtT and DMSxT/DMQqT as the emitting layer. In these configurations, the carrier recombination can be modulated because both DMQtT and DMQqT have energy gaps wider than that of DMSxT.The quantum efficiencies (photons emitted per carriers injected) of the LEDs using DMSxT/DMQtT and DMSxT/DMQqT are about one hundred times and one thousand times larger than that of the LED solely based on DMSxT, respectively. These results indicate that the layered structures are advantageous in increasing quantum efficiency of the emission.
New Developments in Second-Order Nonlinear Optical Polymeric Materials
Authors: Tripathy S. K. , Kim W. H. , Bihari B. , Cheong D. W. , Kumar J.
Published: March 2011

Second harmonic generation from the spin coated films of an asymmetrically substituted polydiacetylene, namely poly ((8-butoxy carbonyl) Methyl urethanyl) l- (5-pyrimidyl) -octa-l,3-diyne (BPOD) is reported for the first time. The Macromolecules assemble to produce the organization responsible for SHG without recourse to poling. d33 of the spin coated film (0.19–0.31 μm thickness) are between 0.78–0.88 pm/V without absorption correction and 3.32–5.57 pm/V after correction. Angular and polarization dependence study of the second harmonic response suggests that the film has in-plane isotropy as a whole and the net dipole is nearly perpendicular to the film surface. Spontaneous orientation of the polymer chains during the film formation seems to be responsible for the noncentrosymmetric alignment of the polymer. SHG from the Langmuir Blodgett films are also reported.
Control of the Mesoscopic Organization of Conjugated Thiophene Oligomers, Induced by Self-Assembly Properties
Authors: Garnier Francis , Yassar A. , Hajlaoui R. , Horowitz G. , Deloffre F.
Published: March 2011

Conjugated oligomers form a fascinating class of molecular semiconductors, which open the perspective of control of electronic and structural properties through the variation of their chemical structure. For analysing the correlation between charge transport and structural properties, sexithiophene, 6T, was substituted by hexyl groups, both on the terminal α positions (α,ωDH6T) and as pendant groups in β position (β,β′DH6T). Structural characterizations by X-ray diffraction show that vacuum evaporated thin films of 6T and α,ωDH6T consist of layered structure in a monoclinic arrangement, with all-planar Molecules standing on the substrate, and that a much longer range ordering is observed when passing from 6T to α,ωDH6T, evidencing a large increase of molecular organization at the mesoscopic level. Electrical characterizations also indicate a significant enhancement of anisotropy of conductivity, with a ratio of 120 in favor of the conductivity along the stacking axis for α,ωDH6T. The charge carrier mobility, measured on field-effect transistors fabricated from these conjugated oligomers, also shows a large increase by a factor of 25 when passing from 6T to α,ωDH6T, and reaches a value close to 10-1cm2V-1s-1. In contrast, ββ′DH6T presents very low conductivity and mobility. These observations are attributed to the self-assembly properties brought by alkyl groups in α,ω position, and confirm the large potential of molecular engineering of organic semiconductors.
Polyimide/Norganic Composite - Interpenetrating Polymer Network For Stable Second-Order Nonlinear Optics
Authors: Marturunkakul Sutiyao , Chen Jeng-I , Li Lian , Jiang Xin Li , Jeng Ru Jong , Kumar Jayant , Tripathy Sukant K.
Published: March 2011

A new class of IPN system has been prepared and investigated. This IPN system combines the polybismaleinimide network and the NLO-active phenoxysilicon network. The second-order NLO coefficients, d33, values of the samples range from 2.5 to 6.7 pm/V depending on the composition and the processing conditions. The temporal stability of the second-order nonlinearities for these samples at 110 °C varies from 47 to 88 % retention after 274 h.
Nonlinear Optical Properties Of Substituted Stilbazolium-MPS3 Intercalation Compounds
Authors: Lacroix Pascal G. , Clement Rene , Nakatani Keitaro , Ledoux Isabelle , Zyss Joseph
Published: March 2011

We have investigated intercalation into optically transparent MPS3 (M = Mn, Cd) phases as a way towards spontaneous poling of cationic chromophores. Two nano-composite Materials of formula M0.86PS3 (dimethylamino-N-Methyl stilbazolium)0.28 were synthezised, and an efficiency up to 750 times that of urea was recorded in the cadmium intercalate. An additional interest arises from the possibility to associate NLO properties with the magnetization of the host lattice in the case of MnPS3 below 40 K.
The Relationship Between Second-Order Nonlinear Optical Properties And Ground-State Polarization
Authors: Bourhill Grant , Cheng Lap-Tak , Lee Ging , Marder Seth R. , Perry Joseph W. , Perry Matthew J. , Tiemann Bruce G.
Published: March 2011

A review is presented describing our recent work to correlate the first hyperpolarizability, β, of organic materials with the molecular parameter bond length alternation (BLA). Donor-acceptor polyenes displaying a wide BLA range were synthesized. For a particular chromophore, BLA was fine-tuned by varying solvent polarity. The degree of BLA was analyzed by X-ray diffraction, 1H-NMR and electronic absorption spectroscopy. Non-resonant, solvent-dependent, electric field induced second harmonic generation (EFISH) Measurements were performed to probe the variation in the second-order nonlinearity as a function of ground-state polarization. The resulting trend, which is fully consistent with theoretical predictions, identified chromophores possessing optimized positive and negative hyperpolarizabilities. An optimized chromophore was incorporated in a polymer matrix and poled. The resulting electro-optic coefficient was found to be significantly enhanced relative to the longer chromophore Disperse Red 1.
Rational Designs of Multifunctional Polymers-Conjugated Photorefractive Polymers
Authors: Yu Luping , Chan Wai-Kin , Chen Yongming , Peng Zhonghua
Published: March 2011

A novel type of photorefractive polymers, containing a conjugated backbone and a second order NLO chromophore, has been developed. A new polymerization method based on the Stille coupling reaction was explored to synthesize these materials. It was expected that the conjugated backbone would absorb photons in the visible region and play the triple role of charge generator, charge transporter and backbone. Several physical measurements demonstrated this expectation. Two beam coupling experiments clearly indicated an asymmetric optical energy exchange between two beams without applying an external electrical field. This is a conclusive demonstration for photorefractivity. Also, large optical gain of 5.7 cm-1 was observed under zero-field condition, which is comparable to most inorganic photorefractive materials. The versatility of the reaction makes possible the advancement of new polymer structures.
Fabrication of Poled Polymer Dans Waveguides and First Observation of Shg by Counter-Propagating Guided Waves
Authors: Otomo Akira , Stegeman George I. , Bosshard Christian , Mittler-Neher Silvia , Horsthuis Winfried H. G. , Möhlmann Gustaaf R.
Published: March 2011

Plane-parallel poled, low loss, channel waveguides are fabricated with a large poling field (200V/μm) in 4-dimethylamino-4'-nitrostilbene (DANS) side-chain polymers. The parallel poled film leads to efficient nonlinear optical applications for TE guided Modes. We demonstrate surface emitting second harmonic generation due to mixing of counter propagating waves with this film.
Laser–Recrystallized SOI Devices: Promises and Pitfalls
Authors: Kamins T I
Published: March 2011

Recrystallized SOI structures offer possibilities for new classes of devices, as well as improved performance of more conventional circuitry. Single-layer and multilayer circuits are possible. For large–geometry devices unseeded films should be satisfactory, but seeding will be required for high–performance, small–geometry circuits. In addition to the quality of the recrystallized film and the substrate, the properties of the interfaces must be optimized. The characteristics of each potential heat source must be considered when selecting one for a specific SOI structure; different sources will be optimum for different applications. The evolution of SOI device structures can be seen by considering different realizations of CMOS cells. SOI structures can be applied to conventional circuits and also should allow efficient integration of entire systems with closely interacting functions.
NMOS Dynamic Shift Registers in CO2 Laser-Crystallized Silicon Thin-Films on Fused Quartz
Authors: Chiang Anne , Zarzycki Mark H. , Meuli William P. , Johnson Noble M.
Published: March 2011

High-speed NMOS depletion-load ring oscillators and dynamic shift registers have been fabricated from laser-crystallized silicon thin-film transistors (TFT's) on fused quartz. We report on optimization of circuit fabrication process involving ion implantation and high temperature cycles to achieve inverter gains, logic thresholds, and input noise margins appropriate for logic operation. Characteristics of discrete devices are also used to evaluate a process simulator and a device simulator as tools for future designs.
Staggered CMOS: A Novel Three-Dimensional Technology
Authors: Maby E. W. , Antoniadis D. A.
Published: March 2011

We report the fabrication of mutually self-aligned IGFET's in two silicon layers which are separated by a thin dielectric film. The transistors are configured such that the heavily doped source and drain regions of a transistor in one layer also serve as the gate electrodes for transistors in the other layer. One application of this three-dimensional technology is the implementation of a compact four-transistor “staggered” CMOS latch circuit which can be used to form part of a static random-access memory cell.
An Epitaxial Regrowth of Polysilicon to Single Crystal Silicon By H2 Annealing Process
Authors: Hirofuji Yuichi , Nomura Noboru , Kugimiya Koichi
Published: March 2011

Si epitaxial regrowth was realized through the thick interfacial oxide films of up to 2 nm by H2 annealing. The epitaxy took place in an anomorous region when the oxide was reduced to about a half of its initial peak height, indicating that about a half of the interfacial oxide films in areawise was completely reduced. In this region, redis-tribution or diffusion of super-saturated oxygen was also observed.

A schematic model of the epitaxial regrowth by H2 annealing is presented.
N-Channel and P-Channel LPCVD Polysilicon Mosfet's and Effects of Grain Boundary Passivation
Authors: Shichijo H. , Malhi S. D. S. , Chatterjee P. K. , Shah A. H. , Pollack G. P. , Richardson W. H. , Shah R. R. , Douglas M. A. , Lam H. W.
Published: March 2011

MOSFETs built in a thin layer of as-deposited, small-grain LPCVD polysilicon offer an attractive alternative to the beam recrystallized SOI MOSFETs because of its simple process and low cost. The inherently inferior performance of polysilicon MOSFET can be improved by the grain boundary passivation in hydrogen plasma. The device characteristics of n-channel and p-channel polysilicon MOSFETs are compared before and after the hydrogen passivation. Dramatic improve-ment of drive current and curtailment of leakage current has been observed after the passivation. The anomalous leakage current has been observed and is attributed to the soft breakdown of the drain junction.
Laser Recrystallization Technique for Active Matrix LC Display
Authors: Nishimura T , Ishizu A. , Matsumoto T. , Akasaka Y.
Published: March 2011

This paper demonstrates the technological approach to the high performance thin film transistor (TFT) fabricated by using the laser-recrystallization technique on a fused quartz wafer and its application for active matrix type liquid crystal display (LCD) with transmissive mode. Problem to be overcome and still ahead in the recrystallization, TFT performance, and application for LCD are addressed.
Applications of CdSe Thin Film Transistors in Flat Panel Displays
Authors: Luo Fang-Chen
Published: March 2011

CdSe TFT's have been successfully utilized in large-area TFT-addressed liquid crystal and electroluminescent display panels. Display panels up to 5″ × 5″ 250 × 250 elements have been demonstrated. CdSe TFTs have exhibited acceptable electrical characteristics, stability and reproductibility for display applications. In this paper, test results of CdSe TFT's in these areas will be reported.

For the fabrication of CdSe TFT matrix circuits for display applications, several methods such as the one-vacuum-pump-down process using aperture masks, the photolithographic process and the hybrid process have been used. A review and comparison of the results of these processes will be presented.
Material Properties Controlling the Performance of Amorphous Silicon Thin Film Transistors
Authors: Powell M. J.
Published: March 2011

Amorphous silicon thin film transistors have been fabricated with a number of different structures and materials. To date, the best performance is obtained with amorphous silicon - silicon nitride thin film transistors in the inverted staggered electrode structure, where the gate insulator and semiconductor are deposited sequentially by plasma enhanced chemical vapour deposition in the same growth apparatus.

Localised electron states in the amorphous silicon are crucial in determining transistor performance. Conduction band states (Si-Si antibonding σ*) are broadened and localised in the amorphous network, and their energy distribution determines the field effect mobility. The silicon dangling bond defect is the most important deep localised state and their density determines the prethreshold current and hence the threshold voltage. The density of states is influenced by the gate insulator interface and there is probably a decreasing density of states away from this interface. The silicon dangling bond defect in the bulk amorphous silicon nitride also leads to a localised gap state, which is responsible for the observed threshold voltage instability.

Other key material properties include the fixed charge densities associated with primary passivating layers placed on top of the amorphous silicon. The low value of the bulk density of states in the amorphous silicon layer increases the sensitivity of device characteristics to charge at the top interface.
a-Si:H TFT: Potential Suitabilities for Gate and Source-Drain Self-Aligned Structure
Authors: Diem B. , Chenevas-Paule A.
Published: March 2011

Performances of a-Si:H TFT's are partly restricted by the parasitic capacitances due to the source-drain/gate overlapping and the channel length. These capacitances are inherent to the conventional photolithographic process [1] and to the MIS structure.

The use of the self-aligned a-Si:H TFT technology should allow the manufacture of short channel TFT's (L < 5 μm) where the overlapping length becomes negligible, on a large area as well as in high definition matrices. Such transistors could constitute in the near future the solution for high performances matrix arrays as well as their peripheral electronics.
A One-Micrometer Channel Length α-Si Thin-Film Field-Effect Transistor
Authors: Yaniv Z. , Hansell G. , Vijan M. , Cannella V.
Published: March 2011

A new method of fabricating short channel α-Si TFTs has been developed. One-micrometer channel length α-Si thin-film field effect transistors have been fabricated and tested. Threshold voltages as low as 1.9V and field-effect mobilities as high as 1 cm 2/V-sec are reported. These devices were fabricated by techniques compatible with the production of large area liquid crystal displays.
Silicon on Insulator by High Dose Implantation
Authors: Hemment P. L. F.
Published: March 2011

Silicon on insulator structures consisting of a buried dielectric, formed by the implantation of high doses of oxygen ions, have been shown to be suitable substrates for LSI circuits. The substrates are compatible with present silicon processing technologies and are confidently expected to be suitable for VLSI circuits. In this paper the microstructure and physical properties of this SOI material will be described and the dependence of these characteristics upon the implantation conditions and subsequent thermal processing will be discussed. With this information, it is then possible to outline the specification for a high current oxygen implanter.
Dielectric Isolation Using Porous Silicon
Authors: Baumgart H. , Frye R. C. , Phillipp F. , Leamy H. J.
Published: March 2011

The fabrication of silicon-on-insulator structures was examined utilizing epitaxial growth of Si films on porous silicon and subsequent enhanced oxidation of the porous substrate. Porous silicon films have been formed by local anodic dissolution of silicon wafers in HF, while retaining the single crystalline structure. Low temperature liquid phase epitaxy (LPE) from saturated Ga solutions as well as molecular beam epitaxy (MBE) and laser induced epitaxy have been studied. Transmission electron microscopy (TEM) has demonstrated that all three techniques can achieve crystalline Si film growth on porous silicon. Surface smoothness and crystal perfection of the resulting epitaxial layers varies considerably with each technique.
Incoherent Light Recrystallization of Silicon-On-Insulator Films
Authors: Robinson Mc D. , Celler G. K. , Lischner D. J.
Published: March 2011

Energy sources used to convert polycrystalline silicon-on-insulator films to single crystal through melting and recrystallization have included electron beams, lasers, graphite strip heaters, and incoherent light from tungsten halogen and vapor arc lamps. This review focuses on incoherent light recrystallization of polycrystalline silicon; comparing tungsten filament and vapor arc lamp sources, and linear zone melting vs. uniform illumination. The discussion includes material redistribution, defect formation, and the dynamics of melting.
Lateral Seeding of Silicon-On-Insulator Using an Elliptical Laser Beam: A Comparison of Scanning Methods
Authors: Zorabedian P. , Kamins T. I.
Published: March 2011

Two scanning methods for laterally-seeded recrystallization of striped silicon-on-insulator/seed structures with an elliptical laser beam are discussed. One method requires repeated remelting of the silicon film and is controlled by the temperature of the substrate, which is locally heated by the beam. This method results in very few defects and single-crystal silicon-on-insulator stripes up to 50 μm wide. The second method involves little remelting and is primarily controlled by the lateral offset of the beam with respect to the stripes. Single-crystal silicon-on-insulator stripes up to 40 μm wide have been obtained, with defects consisting primarily of stacking faults and twins, as well as some grain boundaries. These defects show little effect on MOS transistor leakage current.
Structural Properties of Dielectric Layers Following CO2Laser Irradiation of SOI Structures
Authors: Baumgart H. , Arnold E. , Petruzzello J. , McGee T. F. , Frommer M. H.
Published: March 2011

Semi-insulating polycrystalline silicon films have been used as matching layers in micro-zone-melting recrystallization experiments of silicon-on-insulator (SOI) structures. The effect of the laser irradiation on the structural composition and crystallographic properties has been investigated by transmission electron microscopy and Auger electron spectroscopy. CO2laser processing has been shown to lead to redistribution of oxygen and interface segregation of thin oxide and silicon zones.
Line-Source Processing of SOI Structures with Laser and Electron Beam
Authors: Palkuti Leslie J. , pang Chan-Sui
Published: March 2011

Line-shaped laser and electron beams in combination with halogen-lamp substrate heating were used to fabricate single-crystal SOI films. Electron-beam and laser systems were developed to achieve a minimum beam cross section of 10–100 microns and aspect ratios up to 70. Unseeded SOI films were fabricated with a (100) textured single-crystal structure. Seeded films were recrystallized with 20 × 80-micron single crystal islands with no low-angle grain boundaries. A process window of 1 to 10 percent in electron-beam power was measured. Single-crystal films were obtained at a line-scan velocity up to 2 cm/s suggesting a potential throughput of about 100 wafers per hour. The high scan velocity allows for minimizing the high-temperature cycle to under 30 seconds that the wafer is exposed to during recrystallization. This short temperture cycle is compatible with the fabrication of three dimensional devices, since unwanted diffusion and substrate damage are minimized.
The Effect of Organic Macromolecules on the Vateritet to Calcite Transformation
Authors: Spearing Liisa Kuhn , Sarig S. , Fink D. J. , Heuer A. H.
Published: March 2011

Small quantities of acidic macromolecules were added to crystallizing calcium carbonate in an attempt to engineer crystal growth. The additives are simple analogs to those molecules found in close association with the mineral phase in biological ceramics. When 5 or 10 ppm of the four additives (poly-L-glutamate, poly-L-aspartate, polyacrylate and polymaleate) were added to aqueous suspensions of metastable vaterite, the transformation to calcite was markedly retarded, and the morphology of the final crystal product was altered. The two polypeptides were most effective in inhibiting calcite nucleation and growth; they also promoted vaterite aggregation, and caused the formation of large calcite crystals.
Synthesis of Functionalized Targeted Polyamides
Authors: Mungara P. M. , Gonsalves K. E.
Published: March 2011

A synthetic approach to polyamides containing the tyrosine-leucine linkage is presented. The diphenyl phosphoryl azide, (DPPA), coupling technique was utilized to synthesize the monomers. Solution polymerization of monomer I, tyrosylleucyliminohexamethyleneiminoleucyltyrosine, with adipoyl and sebacoyl chlorides gave polymers with intrinsic viscosities of 0.18 dL/g and 0.13 dL/g respectively in 90% formic acid. Interfacial polymerization of the monomer yielded a fibrous crosslinked material which was found to be a poly(amide-ester) by IR spectroscopic analysis.
Wear and Friction of Unio Crassus Shell in Dry Sliding Contact with Steel
Authors: Hirvonen J-P. , Lappalainen R. , Koskinen J. , Likonen J. , Pekkarinen M.
Published: March 2011

Biological materials such as shells possess a useful combination of mechanical properties. For instance, good fracture toughness combined with a relatively high hardness has been reported. The response of these properties to a tribological performance could presumably be very beneficial. Unfortunately no such research has been reported, although this kind of information is invaluable in possible utilization of biomimetic or biological processes in producing of materials.

In this work chemical composition of Unio Crassus shells were characterized using secondary ion mass spectroscopy (SIMS) and Rutherford backscattering spectroscopy (RBS) and the microstructure was determined with X-ray diffraction (XRD) and scanning electron microscopy (SEM). Specimens of 20×10 mm in size with a thickness of a few millimetres were cut and mechanically polished followed by ultrasonic cleaning in deionized water. Wear and friction measurements were performed in a pin-on-disc tester with a hardened steel pin 6 mm in diameter as a counter face. Tests were carried out in a relative humidity of 50 % at room temperature with a sliding speed of 15 mm/s. The measurements indicate a friction coefficient of 0.3 – 0.4 which is reasonable low. Moreover, wear resistance was found to be excellent. The wear resistance of the material was similar to those of the best synthetic diamond-like carbon films. The storage of the specimen at room temperature for 150 days deteriorated the material resulting in much worse tribological properties.
Biomimetic Lithography and Deposition Kinetics of Iron Oxyhydroxide Thin Films
Authors: Rieke Peter C. , tarasevich Barbara J. , Wood Laurie L. , Marsh Brian D. , Song Lin , Fryxell Glen E. , Engelhard Mark H. , Baer Don R. , John Connie M.
Published: March 2011

Heterogeneous nucleation and crystal growth on protein substrates are critical steps in biological hard tissue formation. Self assembled monolayers can be derivatized with various organic functional groups to mimic the “nucleation proteins” for induction of mineral growth. Studies of nucleation and growth on SAMs can provide a better understanding of biomineralization and can also form the basis of a superior thin film deposition process. We demonstrate that micron-scale, electron and ion beam, lithographic techniques can be used to pattern SAMs with functional organic groups that either inhibit or promote mineral deposition. Patterned films of iron oxyhydroxide were deposited on the areas patterned with nucleation sites. Studies of the deposition kinetic of these films show that the surface indeed induces heterogeneous nucleation and that film formation does not occur via absorption of polymers or colloidal material formed homogeneously in solution. The nucleus interfacial free energy was calculated to be 88 mJ/m2 on a SAM surface composed entirely of sulfonate groups.
Injection Molding of ProNectin®F Dispersed in Polystyrene for The Fabrication of Plastic Ware Activated Towards Attachment of Mammalian Cells
Authors: Stedronsky Erwin R. , Cappello Joseph , David Samuel , Donofrio David M. , Mcarthur Tina , Mcgrath Kevin , Panaro Marilyn A. , Putnam Donna , Spencer William , Wallis Owens
Published: March 2011

ProNectin®F is a recombinant engineered protein polymer of de novo design which incorporates the RGD epitope recognized by mammalian cell integrins. It is biologically active as a cell attachment protein, manifests properties of a planar polymeric surfactant, and is extremely resistant to thermal degradation. ProNectin®F was dispersed onto polystyrene powder, fabricated into plastic ware through injection molding, and the plastic ware was shown to have cell attachment activity. This technology represents a new paradigm for the production of plastic ware useful for mammalian cell culture under serum free conditions; and more generally, for the production of molded devices for use in contact with cells in vitro or in vivo.
Selective Attachment of Synthetic DNA to Self-Assembled-Monolayer Functionalized Surfaces
Authors: Chrisey Linda A. , Roberts Paul M. , Benezra Valarie I. , Dressick Walter J. , Dulcey Charles S. , Calvert Jeffrey M.
Published: March 2011

Self-assembled monolayer (SAM) films of organosilanes have been characterized as surfaces for the spatially-controlled, selective attachment of single-stranded synthetic DNA. Geometric patterns of DNA on silica substrates have been created by photochemical modification of the SAMs to produce regions which promote or resist DNA attachment. The attachment of DNA to the modified surfaces was followed using UV spectroscopy, radioassay, ellipsometry, and enzyme-linked colorimetric assay. We have also demonstrated that immobilized DNA is capable of hybridization with a complementary strand under stringent conditions.
Two-Dimensional Protein Crystals (S-Layers): Fundamentals and Application Potential
Authors: Sleytr Uwe B. , Sara M. , Pum D. , Küpcü S. , Messner P.
Published: March 2011

Crystalline cell surface layers (S-layers) represent the outermost cell envelope component in many bacteria. The oblique, square or hexagonal lattices are formed of assemblies of a single protein or glycoprotein species. Isolated S-layer subunits are endowed with the ability to assemble into monomolecular arrays in suspension, on solid surfaces (e.g. metals, polymers, glass, carbon, silicon), at the air/water interface, or on lipid films generated by the Langmuir Blodgett technique. S-layer lattices are isoporous structures with functional groups located on the surface and in the pores in an identical position and orientation. These characteristic features have led to applications of S-layers as (i) ultrafiltration membranes with pores of identical size and morphology and a broad chemical modification potential, (ii) matrices for the controlled and reproducible immobilization of functional macromolecules, as required for affinity and enzyme membranes, affinity microcarriers and biosensors, (iii) carriers for Langmuir-Blodgett films and reconstituted biological membranes, (iv) immobilization matrices and adjuvants for weakly immunogenic antigens and haptens and (v) patterning elements in molecular nanotechnology.
Formation of Two-Dimensional Crystals of Membrane-Anchored and Water-Soluble Proteins
Authors: Engelhardt Harald , Scheybani T. , Von Gustedt W. , Baumeister W.
Published: March 2011

The formation of two-dimensional (2-D) crystals of biological macromolecules is of interest for nanotechnological applications. Protein 2-D crystals may be used as molecular sieves and/or support devices as components of biosensors etc. [1]. Functionally specialized 2-D crystals, containing transport or catalytic proteins, provide a certain function in a highly efficient and vectorial manner. Future developments may allow the design of more complex structures such as multilayers made from different proteins or arrays of functionally linked oligo- or multimeric complexes consisting of multiple protein species [2]. Regular 2-D arrays, either truely crystalline or densely packed molecules, are one of the basic structures taht might be used to construct more sophisticated protein-based devices. 2-D crystals have some interesting features:
Biomolecular Self-Assembly of Quantum-Dot Composites
Authors: Lawton Carl W. , Fiddy Michael A. , Flynn Geoff , Aboughanem Fadi
Published: March 2011

A biomimetic approach utilizing biomolecular self-assembly was used to tailor quantum-dot composites for use as nonlinear optical media. Yeast tRNA was utilized as an ion-exchange/nucleation site within a polymeric matrix (polyacrylamide). Cadmium ion-exchange and subsequent sulfide precipitation resulted in quantum-dot formation. Illumination of samples with an Argon laser (514 nm) utilizing the Z-scan measurement method resulted in χ3 values of +3.7 ×10−6 esu.
Disulfide Bonds in Recombinant Repeat Units From an Aquatic Insect's Silk Protein
Authors: Case Steven T. , Smith Stanley V. , Bratton Melyssa R.
Published: March 2011

rCAS is a recombinant Constant And Subrepeat (rCAS) protein modelled after tandem core repeats found in a 1000-kDa silk protein synthesized by larvae of the midge,Chironomus tentans. rCAS is encoded by a synthetic gene (synCAS) which is expressed in bacteria. Purified rCAS has four cysteine residues that participate in formation of two intramolecular disulfide bonds. Here we report the results of amino acid sequencing and electrospray ionization mass spectroscopic analyses of tryptic fragments of native and reduced rCAS which suggest that these disulfide bonds are heterogeneous. To assist in studying the formation of disulfide bonds in reduced and refolded rCAS, a series of synCAS mutants were constructed with cysteine to alanine substitutions. In comparison to wild-type rCAS and a Cys79→Ala mutant, the refolding of Cys9→Ala appears to be partially inhibited.
Smart Muscle Under Electrochemical Control of Molecular Movement in Polypyrrole Films
Authors: Otero T. F. , Rodriguez J. , Santamaria C.
Published: March 2011

A bilayer device: consisting of a conducting, flexible polypyrrole layer and an adherent, elastic non conducting film was constructed. One end of the bilayer was fixed with a clamp, allowing the electrical contact with polypyrrole. Polypyrrole volume increases and decreases reversibly during electrochemical oxidation and reduction processes in aqueous solutions. Reversible stress gradient across the flexible film promotes reversible angular movements of the free end of the bilayer, around the fixed end. The effect of the anodic and cathodic potential gradients, as well as the effect of the concentration of movable ions on a 180° angular movement, in the electrolytic solution, were studied. Weights of 1000 times the bilayer weight adhered at the bottom of the bilayer were reversibly trailed across 180° by electrochemically controlled oxidation and reduction processes, in a few seconds. As an electric current promotes chemical reactions giving a change of volume and promoting a mechanical energy, the device was named artificial muscle. Similarities and differences between muscles and artificial muscles are discused.
Biological Self-Assembly: A Paradigm for Materials Science
Authors: McGrath Kevin P. , Kaplan David L.
Published: March 2011

Complex organized systems evolved from the prebiotic soup approximately three billion years ago, relying on simple molecules which spontaneously and synergistically combine to accomplish certain tasks. As life evolved, the sophistication of these interactions also increased. Organisms evolved by linking the needed functional groups together in proteins to improve the efficiency of the process, and now rely almost exclusively on protein interactions to accomplish needed tasks. It is for this reason that considerable effort has been expended on understanding how such complexes are formed and how the individual components contribute to overall function. The code for these interactions lies buried in the amino acid sequences of the constituent proteins. Biologists are beginning to unravel the secrets of this code, and see how small changes to individual residues can affect the overall stability and function of the complex.
Preparation of 6-O-Acyl Amylose Derivatives
Authors: Cimecioglu A. L. , Ball D. H. , Kaplan D. L. , Huang S. H.
Published: March 2011

Two new direct approaches for selective 6-O-acylation of amylose under homogeneous conditions were investigated. In the first method, amylose was initially brominated at C-6 using Nbromosuccinimide and triphenylphosphine in N,N-dimethyfformamide containing lithium bromide. The procedure was found to be highly selective and proceeded with no detectable reaction at the secondary positions. Several 6-bromo-6-deoxyamylose derivatives were prepared with different degrees of substitution by changing the molar equivalence of the reactants. In the second stage these were converted into 6-laurate esters by treatment with cesium laurate in dimethylsulfoxide, which proceeded rapidly under mild conditions. In the second method, the feasibility of 6-O-benzoylation in one step using the Mitsunobu reaction was evaluated. Amylose was treated with diethylazodicarboxylate in the presence of triphenylphosphine and benzoic acid in dimethysulfoxide under ambient conditions. While exclusively 6-O-benzoylation resulted up to degree of substitutions of ca. 0.5, at higher values a small amount of esterification at secondary hydroxyl groups also occurred. Products were characterized by 13C NMR, FTIR and elemental analyses.
Computer Simulations of Nonlinear Optical Chromophore Containing Polypeptides
Authors: Pachter Ruth , Fairchild Steven B. , Lupo James A. , Sennett Brian S. , Crane Robert L. , Adams W. Wade
Published: March 2011

In our continuing efforts towards the design of nonlinear (NLO) optical chromophore containing polypeptides we present an integrated computational approach, in which the design of biomolecular materials with defined secondary and tertiary structures is investigated by means of novel predictive tools, while the effects of the nonlinear optical chromophores are studied with molecular dynamics simulations. A neural network that was trained to predict the spatial proximity of Cα atoms that are less than a given threshold apart, is applied. The double-iterated Kalman filter (DIKF) technique is then employed with a constraints set that includes these pairwise atomic distances, and the distances and angles that define the structure as it is known from the protein's sequence. The results for test cases, particularly Crambin and genetically engineered Eglin-C, demonstrate that this integrated approach is useful for structure prediction at an intermediate resolution. Defined structural motifs of NLO chromophore containing polypeptides are investigated by using molecular dynamics techniques, particularly for the design of coil coiled amphiphatic biopolymers.
Preliminary Characterization of Organic Nucleator and Framework Macromolecules in Mollusc Shells
Authors: Humbert Richard , Sarikayat M. , Aksay I. A. , Crabb J. W. , Furlong C. E.
Published: March 2011

The nacreous (mother-of-pearl) sections of molluscan shells are natural laminates of aragonitic calcium carbonate platelets and an organic matrix. The multi-edged platelets are sub-micrometer thick and surrounded on all sides by 10–20 nm-thick organic matrix that contains several proteins and polysaccharides. Our goal is to identify the components and structure of the organic matrix and determine their function in shell formation and organization. We have extracted organic material from red abalone-Haliotis rufescens, and chambered nautilus-Nautilus pompilius. From the soluble portion, we have partially purified two proteins and determined their amino acid compositions.
Osteoblast - Orthopaedic Biomaterial Response
Authors: Zou L. , Walsh W.R. , Keeping H. , Howlett C. R. , Steele J. , Mcfarland C. , Russell M. , Ehrlich M.G.
Published: March 2011

An understanding of bone cell response and extracellular matrix production to a biomaterial is crucial for development of new prosthetic devices. The nature of the cellular-biomaterial surface interface will depend upon a number of factors including substrate properties (surface chemistry, charge, topography) as well as biological cellular concerns (i.e. adsorption of attachment factors to the surface, growth factors). The quality of the matrix and bone-bonding may be influenced by these factors. Recently, a short-term in-vitro cell culture assay has demonstrated the initial attachment and spread of human derived bone cells on metallic (titanium and stainless steel) and polymeric surfaces to be dependent on the adsorption of adhesive attachment factor proteins (fibronectin and vitronectin) to the substratum surface [1]. The morphological appearance of human osteoblasts cultured on titanium and stainless steel with time also demonstrated differences compared to tissue culture plastic [2]. Little data however, is available for the mitogenic and gene expression levels of primary human bone cells cultured on commonly used orthopaedic materials and the response of these cells to growth factors. The present study examined the mitogenic response and steady state mRNA expression levels of primary human bone cells cultured on metallic substrates to provide further insight into the nature of cell-substrate interactions.