Most conducting polymers used for light-emitting devices have a small electron affinity, creating a high barrier for electron injection resulting in low injection efficiency. To improve injection characteristics, we fabricated and investigated multi-layer contacts with a tunneltransparent dielectric layer of nanometer thickness. Polymer layers were prepared by spin coating, and dielectric and metallic contact layers subsequently grown by vacuum deposition. Samples with such multi-layer cathodes demonstrated a current-voltage characteristic with negative differential resistance. At larger applied voltage, electroluminescence was observed with an efficiency larger than for a simple cathode of the same metal. We have developed a model to describe double injection through multi-layer contacts which explains these salient observed features. The increase in injection efficiency is caused by the voltage drop at the dielectric layer, shifting the metal Fermi level relative to the polymer molecular orbitals responsible for carrier transport. The negative differential resistance is explained by the strong dependence of dielectric tunnel transparency on voltage, a dependence which is qualitatively different for electrons and holes. Further flexibility in the functional characteristics of the injecting contacts is achieved through the use of an additional thin metallic layer playing the role of a base electrode, similar to hot-electron transistors with metallic base.

Surface passivation for the devices is very important for ensuring the DC and RF performances as well as the reliability in pseudomorphic high electron mobility transistors (PHEMT's). We performed the comparative study on the DC, RF and noise characteristics of the 0.1 μm gate length PHEMT's passivated by low dielectric constant benzo-cyclo-butene (BCB) layers with those passivated by the conventional Si3N4 or the. The noise performance of the BCB passivation for the PHEMT's was much superior to that of the Si3N4, whereas the DC and other RF properties were not significantly affected by the passivation materials.

In this paper, we present the syntheses of nano particles of organic / inorganic hybrid for coating on metal or glass surfaces. The organic component is a π-conjugated polymer, polyaniline. The inorganic component is a metal oxide, e.g., cerium oxide. Since the organic component is a water-dispersible polymeric complex of polyaniline and poly(acrylic acid), the hybrid particles are also dispersed in water. The synthesis of the organic / inorganic composite is described. The water dispersible hybrid material was coated on aluminum and glass substrates using a molecular layer-by-layer coating process.

We have developed a current flow analysis system for Field Effect Transistors (FET) using a conductive cantilever of a probe microscope. Using this analysis system, nanoscale current images were observed on a pentacene active layer grown on a bottom electrode in ordinary FETs. When gold (Au) was employed as a bottom electrode, we found the special region around the electrode edge. The current flow hardly occurred in this region. On the other hand, using a conductive polymer (PEDOT) bottom electrode, such a region was not observed. From the detailed observation around the electrode edge, we concluded that the special region would be caused by diffusion of Au particles that evoked heterogeneous pentacene growth, and then the heterogeneity worked as a contact resistance.

Ferroelectric polymer thin films have been investigated for applications such as sensors, MEMS, and memory devices, just name a few. In these thin film devices, it is anticipated that the interface effect will play an important role in determining the device performance. In this paper, we present the results of a recent study on the influence of metal electrodes on ferroelectric switching behavior of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) polymer thin films. The results show that the influence of metal electrodes on the polarization response can be divided into two effects, the bulk effect and interface effect. The bulk effect manifests itself as the built-in bias field when metal electrodes with different work functions were used on the two surfaces of the P(VDF-TrFE) film. The interface effect is more complicated but is directly related to the metal work function. For a metal I/insulator (ferroelectric film)/metal II (MIM) sandwich structure in which the metal I and metal II possess different work functions, the low frequency polarization hysteresis loop shows asymmetric response (different switching fields). The polarization switching time also depends on whether the applied voltage is in parallel or anti-parallel to the built-in bias field. In the fast polarization switching process, it was observed that the interface effect plays a dominating role and the switching time is mainly limited by the charge injection from metal electrodes to the polymer film. For metal electrodes with higher work function, higher injection currents and hence faster polarization switching were observed. The results from I-V studies also show that the charge injection process is a Schottky type and the barrier height estimated from the temperature dependence of the I-V curves is consistent with the metal work functions used.

The aromatic hydrocarbon pentacene is currently under investigation for use as the active layer in electronic devices such as thin film field effect transistors. We have used X-Ray Diffraction (XRD), Electron Diffraction (ED), Low Voltage Electron Microscopy (LVEM), High Resolution Electron Microscopy (HREM) and molecular modeling to investigate the thin film phase of pentacene. We will report the orthorhombic symmetry and lattice parameters of the thin film phase measured experimentally from these techniques. The structure of extended defects such as dislocations and grain boundaries will influence the electrical and mechanical characteristics of the films. Here we show a direct image of an edge dislocation in the thin film phase and discuss the way in which the lattice accommodates the defect.

High frequency contact mechanics experiments were carried with a quartz crystal resonator, the surface of which was coated with a polystyrene film. The experiment is based on the ring-down of the resonator after the electrical excitation has been stopped. When a tip touches the quartz surface, the shear motion of the quartz is perturbed, which can be used to study force-displacement and force-speed relations in the contact zone. A nonlinear spring constant κl(x) and a nonlinear friction coefficient ξl(ẋ) are explicitly derived. When a ceramic sphere touches a polymer film the friction force depends more than linearly on lateral speed. This contrasts to metal-metal contacts or contacts between ceramic surfaces, where the friction force depends either linearly of sub-linearly on speed.

The pre-treatment of aluminium surfaces prior to adhesive bonding and coating processes is of major technological significance. However, the two major commercial pre-treatments, chromic acid and phosphoric acid anodising, both make use of Cr(VI) containing solutions with the attendant problems of waste disposal. The disposal of this harmful solution poses severe environmental problems. Therefore, other environmentally friendly alternatives are being investigated, one of the most popular candidates is the use of one-step pretreatment processes based on organosilane adhesion promoters.

This study examines a model system made from polished aluminium sheet treated with an organosilane; γ-glcidoxypropyltrimethoxysilane (GPS). The interface was characterised by TEM carried out on microtomed sections. The information gained from imaging and Electron Energy Loss Spectroscopy (EELS) analysis revealed a layer of oxide, approximately 70 nm thick. Silicon was found to have been incorporated within this oxide layer. Thus it is suggested that during the curing of the GPS, at elevated temperature, growth of aluminium oxide takes place which gives rise to an Al/O/Si phase.

Copper nuclei was grown on a PET surface in the copper sulfate water solution ambience with only one shot of ArF laser.· General electronic circuit printed boards have been made by sticking the copper foils with adhesive agents after having made the foil surface rough. Consequently, even the printed board of low conductivity might generate a high frequency noise due to the difference between the copper foils and adhesive agents. If atoms composing plastics and metal could be combined by a chemical method instead of the conventional physical methods, a hybrid material made of both plastics and metal would be produced.

We have reported for the substitution of copper atoms on an all-aromatic-polyimide surface by a single shot of ArF laser irradiation In this study, with one single shot of ArF laser, we succeeded in growing the Cu nuclei on the PET film whose ultraviolet absorption is lower than all-aromatic-polyimide. The sample surface was photo-oxidized with the Xe2 excimer lamp in pre-treatment. A fused silica glass was placed on the sample surface, and the sulfate water solution was poured into the gap between the glass and the sample to form a thin liquid layer. Then, the sample was vertically irradiated once by the circuit patterned ArF laser light with the laser fluence of 28mJ/cm2. The photo-dissociated copper atom formed the C-O-Cu bond with active oxygen to sub stitute on the PET surface. The modified sample was, then, immersed in the electro less plating solution at 60 degrees Celsius for 15 minutes; the copper thin film of about 24mm was grown on the modified surface.

We have used photoelectron spectroscopy to study possible modifications in the electronic valence band structures of thin films of C60 due to their deposition on single crystal silicon and polycrystalline copper. The C60 thin films were deposited by thermal evaporation under high vacuum and further characterized by using Raman spectroscopy. We observe significant differences in the valence band structures of C60 thin films deposited on these substrates and attribute them to interactions at the interface.

An equivalent circuit model of electrical conduction in polymer-filler particulate composites was developed in this study. The equivalent circuit was constructed for an individual composite particle with a sub-monolayer of conductive filler, where the filler particles play the role of circuit nodes, and inter-particle contacts are represented by resistors between the nodes. The mathematical representation of the equivalent circuit in the form of a linear system of equations for nodal potentials was solved numerically with Matlab software to calculate conductance of the composite as a function of the amount of conductive filler, filled fraction of the monolayer, filler-to-matrix size ratio and the degree of structuredness (non-randomness) of the filler material. Additionally, percolation concentrations and statistical distributions of composite conductance were calculated as functions of the filler-to-matrix size ratio.

In this paper we have identified a dominant degradation mechanism of blue light emitting polyfluorene (PF) type polymers, which turns the desired blue emission colour of these polymers into an undesired blue-green emission. As shown low energy emission band at 2.2–2.3 eV can be identified as the emission from exciton and/or charge trapping keto defect sites (9-fluorenone sites), which in fact can be regarded as emission of a guest (defect) accidentally incorporated into the π-conjugated PF backbone. We present spectroscopic evidence for the formation of keto defect sites in 9-monoalkylated polyfluorenes (PF-a) which are identified as the source of the strong low energy emission band. Furthermore we show that the keto defects can be generated directly during polymer synthesis as show for the PF-a or can be formed as main channel of an (photo- or electro-) oxidative degradation process as show for the 9-bisalkylated PF.

The potential profiles along the channel of Al/Poly(3-hexylthiophene), PHT film/Au diode from Al to Au electrodes have been measured directly using nanomanipulator with potential probing tips. The steep potential cliff is observed at the interface of Al/PHT, indicating the existence of depletion layer with higher resistance than that of bulk region. For the forward bias, the resistance at the depletion layer decreased significantly and the potential gradient in the PHT bulk region is observed above the onset bias of 1 V. It is found that the contact resistance of PHT/Au is unexpectedly large in spite of the ohmic behavior and also for Al/PHT at forward bias. The effect of light on the depletion layer will be also mentioned. It is stressed that the contact resistances of PHT and metals are significantly important to improve the performance of organic electronics devices.

In order to boost the performance of next-generation silicon integrated circuits, polymers with lower dielectric constant compared to silicon dioxide are required as interlayer dielectrics (ILDs). Ion penetration from surrounding interconnect metal (typically copper or aluminum) or from barrier materials (e.g., tantalum or tantalum nitride) under thermal and electrical stresses can lead to premature failure of the polymers. Hence, ion penetration was studied in hybrid organosiloxane polymer (HOSP) using bias-temperature stressing. Metal/polymer interface chemistry, particularly the presence of interfacial oxygen, was found to play a key role in aiding metal ionization, and subsequent mobile ion penetration into dielectrics.

Thin films of Ultra-Low K materials such as Xerogel (K=1.76) and MSQ (K=2.2) were implanted with argon, neon, nitrogen, carbon and helium with 2 × 1015 cm−2 and 1 × 1016 cm−2 dose at energies varying from 20 to 50 keV at room temperature. In this work we showed that the surface hardness of the porous films is improved five times as compared to the as-deposited porous films sacrificing the dielectric constant up to 15% after implantation (e.g., from 1.76 to 2.0). The hardness persists after 450 °C annealing. It is also shown that implantation can prevent the penetration of chemical gases such as CVD precursors in the Ultra-Low K dielectrics during a CVD process.

Thin films of polyaniline (PANi) have been in-situ deposited onto fused silica plates modified with ruthenium porphyrin and polypyridyl complexes coordinated to self-assembled monolayers of pyridyl-terminated alkylsilanes. Based on UV-vis and AFM studies, PANi exhibits a slower deposition rate and an earlier onset of secondary nucleation on the metal complex-modified interfaces. Electrical conductivity of the HCl-doped emeraldine salt form of PANi is increased to as high as 40 S/cm, relative to <1 S/cm on bare silica, measured under the same conditions and in the absence of any external modification to the polymer films. These changes are attributed to favorable π interactions between the aromatic surface species and the conjugated polymer that lead to a more expanded coil conformation for PANi.

An increasing range of high-K dielectric is becoming available and it is very worth considering incorporating them into polymer TFTs. One of the benefits is that if metal gates are used then aqueous anodisation provides a very simple approach that is compatible with solution based processing. The details of this process are described. High-K dielectrics reduce threshold voltage and, therefore, increase switching speed. Of particular importance is the problem of bias instability. All the results involve the fractionation and controlled doping of poly-3-hexylthiophene.

We have reported recently a novel method for cross-linking conjugated polymers involving a “precursor polymer” route, where the electrochemical method can be used to prepare ultrathin films on conducting metal and metal oxide surfaces. In this paper, we present the design, synthesis, protocol, and recent results in the application of these thin film materials. An emphasis will be given on how these films are characterized in-situ by a combined surface plasmon spectroscopy (SPS) and electrochemical approach. As a methodology, the concept can be extended to new methods of electrodeposition, patterning, and grafting of conjugated polymers on electrochemically addressable metal surfaces. Compared to spin-cast or electropolymerized monomer films, they are very robust both thermally and mechanically. Other applications of these films to sensors, dielectric materials, non-lithographic patterning, etc. are currently being investigated.

There has been much recent interest in polysaccharide coatings for biotechnology applications. We obtained highly wettable dextran coatings applied to flat silicon wafer surfaces through a two-step process: in the first step, the silicon is aminated by the deposition of a self-assembled monolayer of 3-aminopropyltriethoxysilane (APTES); in the second step, polydisperse and low dispersity dextrans with molecular weights ranging from 1 kDa to 100 kDa are covalently grafted along the backbone to the surface amino groups to achieve strong interfacial anchoring. The effect of dextran concentration on film thickness and contact angle is investigated. Atomic force microscopy (AFM) has been employed to characterize surface roughness and coverage of the dextrans as well as the APTES monolayers. The synthetic surfaces were also tested for gas bubble adhesion properties.

Field-effect transistors (FET's) have been directly written onto glass and Si substrates. The FET';s use the regioregular conjugated polymer poly(hexylthiophene) as the active semiconductor, with a formed polyurethane insulator layer and drain, source, and gate electrodes written in Ag. The FET's were fabricated solely by direct writing techniques. The low processing temperatures, the elimination of photolithography, and the flexibility of the direct writing process make this technology especially attractive for low-frequency applications.