This paper reports the fabrication and characterization of polyimide branching waveguides for on-chip optical signal distribution in GaAs-based optoelectronic integrated circuits (OEICs). Low-loss polyimide s-bends and splitters with good splitting ratios and angles considerably larger than similar structures made from inorganic (e.g. LiNbO3) and semiconductor (e.g. GaAs, InP) materials, have been successfully fabricated and tested. The effects of the radius of curvature, splitter angle and cladding materials on the optical losses are discussed.

Manganese bis(hexafluoroacetylacetonate), Mn(hfac)2, reacts with a series of bisnitroxide radicals, 5- R- 1,3- bis(N- oxy- tert- butylamino)benzene 1R (R = H, Cl, and Br), to give 1:1 polymeric complexes of formula [Mn(hfac)2·1R]n. The X- ray crystal structure of the 1H complex reveals that it crystallizes in the monoclinic system, space group P21/n, with a= 9.212(3) Å, b= 16.620(3) Å, c= 20.088(2) Å, β= 98.46(1)°, V= 3042(1)Å3, and Z= 4. The manganese(II) ion and 1H molecule makes onedimensional chains by ligation of the latter serving as a bis(monodentate) ligand to the former. The crystals of the 1H complex undergo transition to a metamagnet at 5.5 K. Similar 1cl and 1Br complexes behave as ferrimagnets with transition temperatures of 5.2 and 5.0 K, respectively.

In the past decade a new class of magnets possessing spins on organic species have been discovered and studied. These magnets can be fabricated at room temperature and may enable useful devices and/or processes. Herein we discuss several of the mechanisms that can enable the stabilization of magnetic ordering and also provide examples of molecule-based magnets.

Precise measurements of low-field magnetization of TDAE-C60 (TDAE; tetrakis(dimethylamino)ethylene) by SQUID magnetometer revealed a clear “remanence” or “irreversibility”, i.e. difference in the temperature dependence between zero-field cooled (ZFC) and field cooled (FC) conditions below the freezing temperature Tf around 10 K. Also, an extremely slow relaxation phenomena of magnetization was observed. These “glassy” characteristics are reminiscent of a “spin-glass” with Tf at about 10 K as the nature of the magnetic ground state of TDAE-C60.

A technique for producing surface-induced liquid crystal nematic alignment is presented. The alignment film is a simple, inexpensive polyamide-imide, which is treated with linearly polarized short wavelength ultraviolet radiation (λ = 254 nm). The alignment performance of UV-aligned layers is shown by optical transmission of the liquid crystal cells to be comparable to that of brushed layers. Strong alignment is produced within minutes of UV exposure and is maintained with long exposures.

Infrared Polymer Dispersed Liquid Crystals (PDLCs) - polymethylmethacrylate host and E7 eutectic liquid crystal mixture - are formed through an adaptation of the thermally induced phase separation process, enabling facile creation of large liquid crystal droplet formation in the polymer host outside of the normal thermodynamic limits. The PDLCs were characterized electro-optically and microscopically. The effects of the processing parameters on the droplet morphology and switching efficiency are analyzed and presented for these systems. Droplet sizes up to 15 &m have been observed with efficient switching characteristics in the 3 - 5 μm range.

This research focuses on the synthesis, processing, and characterization of novel high performance piezoelectric polymers. A series of polyimides containing pendant, polar trifluoro (-CF 3) and nitrile (-CN) groups have been synthesized, electroded and poled. Measurements of the piezoelectric sensor response are presented to demonstrate the relationship between dipole concentration and the level of piezoelectricity for these materials. An understanding of the effect of dipole concentration on piezoelectric properties will enable the molecular design of polymers possessing distinct improvements over state of the art piezoelectric polymers including enhanced polarizability, polarization stability at elevated temperatures, and increased mechanical integrity.

With excellent processibility on silicon integrated circuits and thermodynamically stable polar order, ferroelectric liquid crystals (FLCs) show great potential as components of fast integrated electro-optic modulators. In order to realize this potential, however, an increase in the magnitude of the electronic secona order nonlinear susceptibility χ(2) is required. This has been problematical since functional arrays with large molecular second order susceptibility β orient with improper supermolecular stereocontrol (i.e. with the charge transfer axis normal to the polar axis) when incorporated into traditional FLC structures. Herein we present examples of a new LC structural class designed to achieve the proper supermolecular structure for large χ(2) in FLCs. The observed sign and magnitude of the ferroelectric polarization of the new mesogens extrapolated from smectic C* mixtures is fully consistent with the desired supermolecular structure.

Switchable diffraction grating with 80 “idependently drived transparent stripe electrodes with spatial resolution 40 l/mm based on ferroelectric liquid crystal is presented. The switching of the diffraction angle till frequency 1kHz is demonstrated using the computer choise of assemblies of electrodes.

A family of electrically conductive polymers based on 3,4-ethylenedioxythiophene (EDOT) and its derivatives will be discussed as electrochromic and redox electroactive materials. Poly(alkylethylenedioxythiophenes), derivatized with octyl and tetradecyl pendant chains, exhibit significantly faster redox switching characteristics than the unsubstituted parent polymer. Bis(2-(3,4-ethylenedioxy)thienyl)arylene (BEDOT-Ar) and vinylene monomers electropolymerize at low potentials avoiding degradative side reactions. We outline the properties of EDOT polymers which exhibit low band gaps allowing for the formation of conductive complexes with a high degree of visible light transmission and show their electrochromic properties. The BEDOT-vinylene polymer, for example, has a band gap of 1.4 eV. A relatively high degree of electrochromic contrast is found at 600 nm as the polymers switch between insulating deep purple absorptive and conductive light blue states. Solid-state dual polymer electrochromic devices have been constructed using a combination of complementary anodically and cathodically coloring polymers based on the EDOT core.

We describe the factors affecting the electron transfer process between the different components of a self-assembled mixed monolayer. The system is comprised of mixed monolayers containing aminoalkanethiols (AMATs) and ferrocenylalkanethiols (FATs) of variable chain lengths. We study the effects of different ratio of the two mixed monolayer components on the permeability of the monolayer towards a Ru(NH3)6C13 redox probe. In order to study the electrical communication between the enzyme and the mediator molecules, the enzyme glucose oxidase (GOx) was attached to the AMAT sites to create a biosensor device. The relative efficiency of a biosensor of each chain-length combination of FAT and AMAT was examined. In light of this comparison, we consider the critical factors for efficient electron transfer between the ferrocene mediator and the GOx redox active site immobilized as part of the surface-confined system. We find that the biosensor response is greatest when the enzyme and the FATs are attached to the surface with different alkane chain lengths. We also find strong evidence for the existence of domains of FAT and AMAT in the mixed monolayer system.

Thin films of organic nonlinear optical materials have become of increasing interest for potential electro-optic and nonlinear optical applications. Organic molecular layer deposition (OMLD) consists of an alternating evaporation of suitable difunctional monomers under UHV conditions and allows self-terminating monolayer growth and in-situ polymerization of periodic structures. Film stability is increased due to chemical bonding between the alternating layers. Moreover, in contrast to epitaxial growth techniques, the choice of interesting inorganic substrates is not limited by lattice-matching conditions. We have investigated the xperimental requirements for OMLD in detail, with pyromellitic acid dianhydride (PAD), terephthalic acid dichloride (TOC), and 4,4′-diamino-diphenylether (DDE) as prototype precursors. After optimization of material fluxes and growth temperatures, covalently bonded monolayers were formed via a self-terminating surface reaction while excessive material was desorbed.

The layer-by-layer self-assembly of a number of different functional dye molecules has been accomplished via the alternate spontaneous adsorption of polyelectrolytes and ionic dyes from dilute solutions. Multilayer thin films containing such functional dyes as pH indicator dyes, infrared absorbing dyes, porphyrin dyes and various fluorescent dyes have been successfully fabricated and their electrical and opt, 2al properties examined. Multilayers containing a newly synthesized ionic ruthenium based polypryidyl dye have been utilized to fabricate light emitting thin film devices with high brightness (ca. 100 cd/m2) at voltages in the range of 5–10 volts. These new light emitting thin film devices exhibit excellent stability when compared to devices based on conjugated polymers such PPV. The fabrication and device evaluation of new heterostructure thin films based on this new light emitting dye as well as the properties of other multilayer thin films containing dye molecules are presented.

Described is the solid-phase and solution-phase synthesis of oligo(2-dodecylphenyleneethynylene) s via an iterative divergent/convergent approach. Synthesized were the monomer, dimer, tetramer, octamer and 16-mer of the oligo(2-dodecylphenylene-thynylene)s. The synthetic protocol for the synthesis and attachment of protected thiol-containing end groups is also described which may serve as molecular alligator clips for adhesion to gold surfaces. These oligomers may act as molecular wires in molecular electronic devices.

A number of approaches to the design and synthesis of conducting polymer-based sensory materials are presented. To elicit a selective sensory response synthetic receptors have been integrated into the polymers such that binding of an analyte produces electronic, electrostatic, and/or structural perturbations. A key element is the use of assemblies of many receptors which are “wired in series” by a conjugated polymeric structure. It is demonstrated that this configuration produces an inherent sensitivity gain over single isolated receptor-based sensory molecules.

We have fabricated thin film transistors (TFTs) using ca-sexithienyl (α-6T) as the active material and have investigated the dependence of transistor characteristics on the choice of source/drain contact metal. Using α-6T synthesized from terthiophene and purified by vacuum gradient sublimation, we have fabricated TFTs with material deposited by evaporation onto substrates held at both room and elevated temperature. We have studied devices fabricated by depositing the active material onto previously patterned source/drain contacts and also by depositing the source/drain contacts after the active layer deposition, in both cases with the gate contact and dielectric underneath the active material. For both device types we find a clear dependence on the choice of source/drain contact metal with correlation to the metal work function. For our devices the best performance is obtained using metals with largest work function (Pd, Pt, or Au), intermediate performance is obtained using a metal with somewhat smaller work function (Cr), and significantly degraded performance is obtained using a metal with relatively small work function (Al). Despite the apparent correlation to the metal work function, we cannot yet rule out oxidation or other chemical effects with the more reactive metals. We have also examined doping of the α-6T layer as a possible route to improved contacts and find that FeCI3 can be used to shift the threshold voltage of α-6T TFTs by more than 50 V.

We provide experimental evidence of a transition from thermally activated hopping of small polarons to band transport of delocalized polarons in polycrystalline oligothiophene fieldeffect transistors. We demonstrate that these transport mechanisms are intrinsic, i.e. governed by material-specific parameters such as the electronic overlap integral and the polaron binding energy. At high temperatures the field-effect mobility decreases with decreasing temperature and the transport mechanism is thermally activated hopping. Below a critical temperature Tτ, the field-effect mobility abruptly increases by more than two orders of magnitude and the transport becomes band-like. This behavior is consistent with the theory T. Holstein developed in 1959 for small polaron transport.

We report measurements made on the photovoltaic effect in devices fabricated with thin films of α-sexithienyl (αT6) as the active layer. aT6 was sublimed onto glass/ITO substrates (as the positive contact), and the substrate temperature was varied between room temperature and 156°C during sublimation to control the film morphology. As the substrate temperature increases, the average size of the αT6 grains increases, from ˜200nm at 22° C to ˜1500nm at 150°C, and order within the grains increases. Aluminium metal was evaporated onto the αT6 as the top (negative) contact.

The dark current-voltage (I-V) curve is strongly rectifying, whereas under illumination it becomes almost symmetrical about ˜0.7V on the voltage axis, which represents the maximum open-circuit voltage. This behaviour indicates that the efficiency of charge separation is strongly bias dependent, and that charges are separated by the bulk field rather than at, for example, a Schottky barrier. The spectral response of the photocurrent is independent of the film morphology, which is surprising since the environment in which excitons recombine radiatively in αT6 is known to depend on the morphology of the film. The spectral response is consistent with previous measurements on photoconductivity, indicating that the efficiency of charge separation increases with increasing photon energy. There is also a significant photocurrent at energies well below the absorption edge of αT6, suggesting an exponential distribution of defect states extending at least 0.6eV into the optical gap, which may be a distribution of X-traps below the absorption edge. As the substrate temperature during growth increases from 28C to 150C the efficiency of charge separation decreases by an order of magnitude, suggesting that exciton dissocation is assisted by traps or defects which are present in smaller numbers in the more ordered films.

A new type of dendritic molecules containing p-phenylene repeat units has been synthesized. Preliminary results on linear and nonlinear optical properties are discussed.

Thin films of electroconductive poly[pyrrole-co-3−(1−pyrrolyl)propionic acid] were prepared by electropolymerization onto 3-aminopropyltrimethoxysilane modified and 3−(1−pyrrolyl)propionic acid derivatized interdigitated microsensor electrode (IME) arrays. The ω−(1−pyrrolyl) moiety on the surface of the device provides for specific adhesion of the polymer film to the device and the (N-pyrrolyl)propionic acid moiety on the polymer backbone provides for covalent attachment of bioactive molecules, such as biotin and urease, to the polymer surface. The immobilized, bioactive urease produces an ON/OFF conductimetric response traceable to analyte concentration.