bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymer Physics Of High Temperature Polymers For Second Order Nonlinear Optics
Authors: Stacey Fu C. Y. , Prdddy Duane B. , Lyle Greg D. , Mcgrath James E. , Lackritz Hilary S. 
Published: March 2011

ABSTRACTA new class of high temperature polymeric materials capable of second order nonlinear optical effects has been developed and characterized. These polymers, Bisphenol A-poly (arylene ether) phosphine oxides (Bis A-PEPO), F6 Bis A-PEPO, phenolphthalein•PEPO (PP-PEPO), and phenolphthaIein-anilide•PEPO (PP-PEPO), doped with nonlinear optical chromophores are being examined using second harmonic generation. Corona poling is used to orient the chromophores into the noncentrosymmetric structure required to obtain the second harmonic signal. These high glass transition temperature (>200°C) polymers have strong hydrogen bonding sites that can interact with the chromophores. This work describes the basic polymer physics including local Mobility, chromophore/polymer interactions, and polymer steric effects that control the thermal and temporal stability of chromophore orientation in these guest-host polymeric systems.
Novel Organic Sol-Gel Materials For Second-Order Nonlinear Optics
Authors: Jeng R. J. , Hsiue G. H. , Chen J. I. , Marturunkakul S. , Li L. , Jiang X. L. , Masse C. , Kumar J. , Tripathy S. K. 
Published: March 2011

ABSTRACTA new class of organic sol-gel second-order nonlinear optical (NLO) Materials based on hexa (Methoxymethyl) Melamine has been investigated. NLO active chromophores, 4- (4′-nitrophenylazo) aniline and 4-amino-4′-nitrobiphenyl, were incorporated into the Melamine Matrices. Samples exhibit second-order optical nonlinearity after poling and curing at 220 °C for 30 Min. The synthesis, preparation, and characterization of these materials are reported.
Laser-Induced Pretransitional Ordering And Nonlinear Optical Properties Of Rigid-Rod Polymer Suspensions
Authors: Vugmeister Boris E. , Malcuit Michelle S. , Kralik John C. , Stevens Colleen 
Published: March 2011

ABSTRACTWe investigate the pretransitional behavior in laser-induced alignment of rigid rod-like polytetraflouroethylene (PTFE) suspensions. Using a laser-induced birefringence experiment, we measure both the orientational order parameter and the orientational relaxation time. We find that both increase as the volume fraction of colloidal particles approaches the critical value for the isotropic-nematic phase transition. Experimental results are compared with theory which takes into account the possibility of a first-order phase transition induced by a laser electric field.
Negative Third Order Optical Susceptibilities of Squaraines
Authors: Shi R. F. , Zhou Q. L. , Garito A. F. 
Published: March 2011

ABSTRACTQuantum Many-electron calculations based on Multiple-excited configuration interaction have been implemented on squaraine Molecules. It is found that certain squaraines possess negative third order optical susceptibilities (γ) even in the zero frequency limit. Our calculations agree well with the experimental results obtained by Dirk and co-workers[1] for anilinium squarylium (BSQ) in terms of the sign and Magnitude. High-lying two-photon states in squaraines are found to be always critically important. The sign of γ is found to depend on the electron donating ability of the two side groups in squaraines.
Demonstration of Dispersive Optical Bistability With a Third Order Nonlinear Optically Active Polymer
Authors: Druy Mark A. , He Guang S. , Casstevens Martin K. , Burzynski Ryszard 
Published: March 2011

ABSTRACTDispersive optical bistability in a Fabry-Perot (F-P) cavity with a third order nonlinear optical polymer was demonstrated. This effort involved the development of several nonlinear optical polyimides and an evaluation of their linear optical and nonlinear optical properties. These Materials were processed into waveguiding films having good homogeniety and optical properties. Several of these films were shown to have desirable third order nonlinearities, while exhibiting good mechanical and environmental stability. Characterization of these materials involved the measurement of their absorption profiles, film thicknesses, optical waveguide propagation constants and nonlinear optical susceptibilities. Based on the measured results, a specific polyimide was chosen and used to demonstrate an all-optical instrinsic bistable device operating at a wavelength of 1.06 μ. Using ∼ 100 ps input pulse widths at 1.06 μ, dispersive optical bistability originating from the induced refractive index change, δn, due to an electronic nonlinearity of the polyimide was observed.
Novel Polydiacetylenes as Materials for Second and Third Order Nonlinear Optics.
Authors: Kim W. H. , Masse C. E. , Bihari B. , Kumar J. , Tripathy S. K. 
Published: March 2011

ABSTRACTThe objective of this investigation was to develop stable nonlinear optical (NLO) Materials which possess both second and third order NLO properties. These Materials were envisioned as having a polydiacetylene (PDA) backbone with a second order active NLO chromophoric substituent consisting of a donor group, a π-conjugated bridge, and an acceptor group. The choice of a PDA backbone in this investigation was twofold. In terms of third order NLO properties, the extensive π-conjugation of the PDA backbone leads to large ultrafast third order effects. In terms of second order NLO properties, the high thermal stability and rigidity of the PDA Matrix in a perfect polymeric single crystal is expected to prevent the randomization of the NLO chromophores in the noncentrosymmetric environment. This paper focuses on the synthesis and NLO properties of the unsymmetrical diacetylene Monomers, ((9-Butoxy carbonyl) Methyl urethanyl) -l- (4-urethanyl-4'-nitrobiphenyl) -nona-2,4-diyne, and ((9-Butoxy carbonyl) Methyl urethanyl) -l- (4-urethanyl-4'-nitroazobenzene) -nona-2,4-diyne. The high entropy flexible urethanyl side group was chosen to satisfy the monomer packing requirements for polymerization and enhance the solubility of the PDAs.
Temperature Dependence of the Exciton-Exciton Annihilation Rate Constant in Poly (Di-N-Hexylsilane)
Authors: Kepler R. G. , Soos Z. G. 
Published: March 2011

ABSTRACTFluorescence depolarization studies of polysilane chains in solution have shown that energy transfer along the polymer chains occurs for only a very short time relative to the excited state lifetime and only over short distances before the excited states become trapped in long, low-energy segments. However, in solid films we have shown in previous work that excitons are highly Mobile throughout their 600 ps lifetime at room temperature, presumably because energy transfer among neighboring, parallel chain segments becomes possible. In this paper we report that the exciton-exciton annihilation rate constant decreases by only a factor of five between room temperature and 12 K, showing that the excitons do not become trapped even at low temperatures.
Observation of Excitonic n-Strings In A Quasi-one-Deviensional Charge-Transfer Crystal
Authors: Peyghambarian N. , Meissner K. , Fluegel B. , Mazumdar S. , Guo F. , Kuwata-Gonokami M. , Sato Y. , Ema K. , Shimano R. , Tokihiro T. , Ezaki H. , Hanamura E. 
Published: March 2011

ABSTRACTCollective excitations, such as plasmons, rotons, electron-hole liquid, and excitonic Molecules, have been extensively studied in condensed Matter.1 Wannier excitons in inorganic semiconductors are bound by the exchange interactions between two electrons of the exciton, and the bound state of More than two excitons is not possible. We demonstrate here a new type of collective excitations,2 bound states of Multiple charge-transfer (CT) excitons. Coulomb interactions in one dimension are shown to bind a train of several (More than two) CT excitons. Experimental evidence for these new type of elementary excitations is reported in a quasi-one-dimensional CT crystal of anthracene PMDA. High density excitation by femtosecond light pulses generates Multi-exciton chains, which we refer to as excitonic n-strings with n = 1, 2, 3, etc., along the stack axis of the crystal. Both the n = 2 excitonic string (biexciton) and the n = 3 string (tri-exciton) are observed. This report provides evidence for an n > 2 exciton chain in this system.2 The stability of the n-string exciton is supported by our theoretical calculations based on the extended Hubbard Hamiltonian in one dimension.
Novel Oxidative Nucleophilic Chemistry Enroute to The Synthesis of C60 Fullerols
Authors: Chiang Long Y. , Wang Lee Y. , Swirczewski John W. 
Published: March 2011

ABSTRACTWe have demonstrated a novel cyclosulfation chemistry for the functionalization of C60 Molecules and a new route to the synthesis of fullerol. The cyclosulfation reaction of C60 was performed in neat fuming sulfuric acid at 55–60 °C under N2. Hydrolysis of these derivatives in the presence of water at 85–90 °C or in aqueous NaOH solution at ambient temperature gave the corresponding polyhydroxylated fullerenes (fullerols) in high yield. Various spectroscopie methods were used to resolve the chemical structure of fullerol. An average of 10 to 12 hydroxyl addends was found in fullerols that can be correlated to the structure of polycyclosulfated fullerene precursors containing 5 to 6 cyclosulfate units. The cyclosulfation chemistry is, presumably, initiated by an one-electron oxidation reaction on C60 Molecules, followed by the attack of nucleophilic anionie sulfate species onto the resulting cationic C60 radical intermediates. Further electron oxidation and intramolecular cyclization of the resulting hydrogen sulfated C60 yielded the desired polycyclosulfated C60 products.
Diacetylene Containing Polyesters and Segmented Polyurethanes with Body Temperature Sensitive Thermochromic Transitions
Authors: Zemach Ken D. , Rubner M. F. 
Published: March 2011

ABSTRACTSeveral diacetylene containing polyesters with thermochromic transitions at or around room temperature have been synthesized. Some of these polymers have been shown to be highly sensitive to body temperature, giving rise to either reversible or irreversible thermochromic changes, depending upon both the molecular structure and the processing conditions. By changing the structure and processing conditions, the thermochromic transition can be moved over a wide range of temperatures. Segmented polyurethanes using these diacetylene functionalized polyesters as soft segments and containing diacetylene groups in the hard segments have also been produced. Through a selective polymerization process, it is possible to selectively cross-polymerize the hard segment diacetylene groups or cross-polymerize both the hard and soft segments thereby making it possible to examine the effects of hard and soft segment crosslinking on mechanical properties.
Dielectric and Absorbate Effects on the Optical Properties of Phosphazenes
Authors: Ferris KIM F. , Samuels W. D. , Morita Y. , Exarhos G. J. 
Published: March 2011

ABSTRACTThe optical response of polyphosphazenes can be directly related to the π (out-of-plane) and π′ (in-plane) bonding interactions intrinsic to the electronic structure of these Materials. Altering this structure either by hydrogen bonding or absórbate effects, affects both the linear and nonlinear optical susceptibilities. In this paper, we have performed electronic structure calculations on the cyclic Molecules, P3N3 (NHCH3)6, P3N3(SCH3)6, P3N3 (OCH3)6 and P4N4 (NHCH3)8 as model systems for the polymer. Charge distribution arguments are discussed to explain the influence of a polarizing electric field on the π bonding systems, and are used to suggest methods to enhance their nonlinearities.
Dielectrically Confined Excitons and Polaritons in Natural Superlattices -Perovskite Lead Iodide Semiconductors
Authors: Gippius N. A. , Muljarov E. A. , Tikhodeev S. G. , Ishihara T. , KELDYSH L. V. 
Published: March 2011

ABSTRACTA large class of new layered semiconductors — lead iodide compounds — is of great interest because of possible optoelectronic applications due to pronounced excitonic effects. These compounds may be regarded as naturally grown semiconductor/insulator superlat-tices, with perovskite lead iodide (semiconductor) layers sandwiched by alkylammonium (insulator) layers. Exciton binding energies and oscillator strength in these structures are enhanced due to the so-called “dielectric confinement” caused by large difference between dielectric constants of adjoining layers. The binding energies, wave functions,& diamagnetic coefficient of excitons in these naturally grown superlattices are calculated with allowance for the image potential and the superlattice structure of the compounds. The localization of excitons in lead iodide layers causes also a strong dependence of a polariton spike in reflection spectra on the polarization of electromagnetic wave. The results obtained are in agreement with the experimental data.
Negative Magnetoresistance in Activated Carbon Fibers Heat-Treated Above 2000°C
Authors: Fung A. W. P. , Wang Z. H. , Dresselhaus M. S. , Dresselhaus G. , Endo M. 
Published: March 2011

ABSTRACTActivated carbon fibers (ACFs) were heat-treated at temperatures above 2000°C to study both the effect of heat treatment on the order development in ACFs and the effect of granularity on the transport properties of granular materials in general. The electrical conductivity σ(T) and Magnetoresistance (MR) were measured as a function of temperature for ACFs Made of two different precursors and heat-treated at different temperatures. While the field dependence of the observed negative MR could be fit to the two-dimensional weak localization (2D WL) theory at each measurement temperature, σ(T) showed only a weak temperature dependence, inconsistent with the ln (T) dependence predicted by the same theory. Even More interesting is the observation of a negative MR, which is a quantum-Mechanical phenomenon, near room temperature. It is thought that the grain boundaries might be responsible for such deviations from the standard 2D WL theory.
Optimization of Conducting Polymer Synthesis for Battery Applications
Authors: Otero T. F. , Santamaria C. , Rodriguez J. 
Published: March 2011

ABSTRACTThe evolution of the capacity to store electrical charges of electrogenerated polypyrrole and polythiophene films, as a function of the parameters of synthesis (electrical potential, solvent, Monomer concentration and temperature) was analyzed. The polymer production was followed by “ex situ” ultramicrogravimetry. The stored charge in each film was controlled by voltammetry and chronoamperometry, in the background electrolyte (in absence of Monomer). The charge storage ability was calculated from the ratio between stored charge and polymer mass adhered to the electrode. The charge storage ability of an electrogenerated film decreases several times when one of the parameters of synthesis: potential of polymerization, temperature, concentration of monomer or donor number of the solvent, increase. The change on the polymer property when the conditions of synthesis shift, points to a mixed polymerization-degradation process during polymer growth. The knowledge of those variations allows to optimize the conditions of synthesis to generate conducting polymers for specific batteries applications.
Electronic Deep Levels in Laser – Crystallized Silicon Thin-Film MOS Capacitors on Fused Silica
Authors: Johnson N. M. , Moyer M. D. 
Published: March 2011

ABSTRACTResidual electronic deep levels in fully – processed, cw laser – crystallized silicon thin films on fused silica were measured by transient capacitance spectroscopy, supplemented with capacitance – voltage techniques. The test devices were metal – oxide – silicon thin – film capacitors with p – type conductivity. The hole emission spectra are dominated by a continuous distribution of deep levels in the lower half of the silicon band gap which are associated with the Si – SiO2 interface; the spectra also display the effects of surface generation. The interface – state density near midgap is estimated to be 6×1010 eV−1 cm−2, and there are no detectable bulk deep levels with densities > 1×1014 cm−3.
Offset-Gate Structures for Increased Breakdown Voltages in Silicon-On-Insulator Transistors
Authors: Drowley C. I. , Kamins T. I. 
Published: March 2011

ABSTRACTAn offset-gate structure was used to fabricate p-channel MOS transistors in laser-recrystallized silicon-on-insulator (SOI) films. The breakdown voltage increased from about -18 V with a conventional gate structure to about -38 V with the offset gate and was then limited by bulk breakdown in the film, rather than by the high fields near the gate drain overlap region. Simulations indicate that breakdown voltages of about -60 V can be achieved in the structure used, provided that the back-surface fixed-charge density is limited to 1×10″ cm−2.
A 3-D Integration Strategy in VLSI
Authors: Malhi Satwinder D. S. 
Published: March 2011

ABSTRACTNearly two decades of work in fabricating active devices in small grain LPCVD polysilicon by various workers has shown that the material is generally suitable for junction diodes and MOSFETs [1–10]. Recently, there has been a considerable activity in the domain of beam recrystallization of polysilicon. One of the goals of this effort is 3-D integration for VLSI. These recrystallization techniques require several years of industrywide effort before they become acceptable tools in IC manufacturing. However, there exists a great demand today, especially in large memories, for an SOI MOSFET that can be integrated in existing bulk silicon based technologies.Fortunately, acceptable MOSFETs can be manufactured in small grain poly-silicon without resorting to beam recrystallization [11–13]. One consistent problem with small grain polysilicon MOSFETs has been a high threshold voltage, which makes these devices unacceptable for standard IC applications that require 5V operation. It has been shown that this characteristic can be remedied by proper device design [11–13]. In particular, thin gate insulator, accumulation mode behaviour, and some form of grain boundary passivation, used alone or in a combination, are effective means of reducing threshold voltage.The other problem of the polysilicon devices has been high leakage current. This is a result of defects in polysilicon. It has been shown that grain boundary hydrogenation drastically reduces the leakage current by passivating these defects [11–13]. As a result, it is possible to manufacture MOSFETs, in small grain LPCVD polysilicon, with on to off current ratio of seven orders of magnitude.With improved device design, it has been possible to build short channel p-channel and n-channel MOSFETs with arbitrary threshold voltage and leakage current of the order of 1 pA/μm channel width. The channel mobility is about 10 cm2/V sec. The on to off current ratio is about seven orders of magnitude. Despite the low mobility, these devices are useful for a variety of high density memory applications.Since no nonstandard materials, tools and processes are required in the fabrication of these devices, manufacturable 3-D integration processes are presently possible with such devices. Besides permitting useful products today, this strategy allows construction of a design and manu-facturing infrastructure that will facilitate infusion of future 3-D concepts in bulk silicon technologies.We have used p-channel devices built in small grain LPCVD polysilicon to develop a 2 μm stacked CMOS process. We have fabricated 64K static RAMs with this process. The cell size is 307 sq.μm and chip size is 55000 sq. mils. The access time is 120 ns. This provides a demonstration of our strategy.
Amorpiious Silicon Thin Film Transistor and its Applications to Large-Area Electironics
Authors: Tuan H. C. 
Published: March 2011

ABSTRACTIn this paper, the amorphous silicon thin film transistor (a-Si:HTFT) technology is reviewed. Its applications to both one- and two-dimensional large-area devices are described. The issues related to the fabrication of TFT arrays on large-area substrates are also discussed.
Vertical-Type a-Si:H Field-Effect Transistors
Authors: Uchida Yasutaka , Matsumura Masakiyo 
Published: March 2011

ABSTRACTVertical-type a-Si:H Field Effect Transistors with 1 μm channel length have been investigated. A simple analysis of the FET characteristics indicates that the reduction of the channel length is an effective method to improve the FET characteristics at least up to the channel length of 1 μm. Experimental results showed that the on-resistance is approximately propotional to the channel length and that on off current ratio of the vertical-type FET with 1 μm channel length was more than 104.
Characteristics of Amorphous Silicon Based Alloy Field Effect Transistors
Authors: Shur M. , Hack M. , Hyun C. 
Published: March 2011

ABSTRACTWe have developed a new theory to describe the current-voltage characteristics of amorphous silicon based alloy field effect transistors. We show that the transition from below to above threshold operation occurs when the Fermi level in the accumulation region moves from the deep to tail localized states in the energy gap and that the field effect mobility is dependent on gate voltage. We also propose a new technique to determine the flat-band voltage from the I-V characteristics in the below threshold regime.
Biologically Derived Nanometer-Scale Patterning on Chemically Modified Silicon Surfaces
Authors: Holland Bradford W. , Douglas Kenneth , Clark Noel A. 
Published: March 2011

ABSTRACTIn recent experiments we have patterned smooth HOPG surfaces with periodic arrays of nanometer dimension holes on a 20nm lattice using two-dimensional (2-D) protein crystals as templates. The bacterial cell wall crystals were deposited on HOPG substrate and overcoated at oblique incidence with an ultrathin (3.5 nmn) TiO2 film. Fast atom beam (FAB) milling patterns the TiO2 film into a screen having the protein lattice periodicity and the screen then acts as a mask for the pattern transfer to the HOPG substrate. This method provides an inexpensive, “benchtop,” intrinsically parallel technique for the periodic nanostructuring of surfaces. Here we extend it to the patterning of silicon single crystal surfaces. We will describe the use of silane coupling agents to enable protein adhesion with the cytoplasmic side up, as is preferable for the patterning. We will show AFM images of the T1O2 -protein-silicon composite surface at various stages of the fabrication process.
Bioactive Silk-Like Protein Polymer Films on Silicon Devices
Authors: Anderson J. Philip , Nilsson Susanne C. , Rajachar Rupak M. , Logan Randy , Weissman Neil A. , Martin David C. 
Published: March 2011

ABSTRACTCoatings of genetically engineered protein polymers based on the crystalline segment of B. Mori silk fibroinand cell binding domains from extracellular matrix proteins (ProNectin™ by Protein Polymer Technologies, Inc.) were applied to bare silicon wafers used to mimic microcircuit devices. These silicon devices have applications in the stimulation and monitoring of central nervous system activity but need bioactive coatings for integration into nervous tissue. Gel point coating technology was developed by preparing solutions at the onset of phase separation in protein polymer/formic acid/ ethanol systems. Dipping silicon wafer substrates into such solutions produced homogeneous thin protein polymer coatings. Quench coating techniques that create rough surfaces in a controlled manner were explored by driving protein polymer solutions through different regions of the protein polymer/formic acid/methanol system before drying. Atomic force microscopy was used to characterize the protein films.