Modification/doping

Photoelectrical properties of phthalocyanine powders and their films on a variety of substrates have been the object of numerous investigations. Photoconductivity is affected by the nature of the phthalocyanine substrate as well as its crystal modification, doping agents employed [201], and by the way the... 

Although a great number of compound semiconductor devices make use of epitaxy to form the cote vertical stmcture of the device, ion implantation (qv) is a powerful tool in creating both horizontal and vertical modifications to a device. Ion implantation can be used to dope a semiconductor either fi- or / -type by using appropriate species. Implantation can also be used to render a region semi-insulating or to initiate multilayer intermixing. 

Historically, materials based on doped barium titanate were used to achieve dielectric constants as high as 2,000 to 10,000. The high dielectric constants result from ionic polarization and the stress enhancement of k associated with the fine-grain size of the material. The specific dielectric properties are obtained through compositional modifications, ie, the inclusion of various additives at different doping levels. For example, additions of strontium titanate to barium titanate shift the Curie point, the temperature at which the ferroelectric to paraelectric phase transition occurs and the maximum dielectric constant is typically observed, to lower temperature as shown in Figure 1 (2). 

At the present time, doped ICPs are not normally capable of being processed like normal thermoplastics. Processes usually Involve high-pressure moulding of finely powdered polymers under vacuum or an inert gas. However, modification of some ICPs with, for example, alkyl or alkoxy side groups may produce soluble, and thus more tractable, polymers. 

The structure-property relations of fullerenes, fullerene-derived solids, and carbon nanotubes are reviewed in the context of advanced technologies for carbon-hased materials. The synthesis, structure and electronic properties of fullerene solids are then considered, and modifications to their structure and properties through doping with various charge transfer agents are reviewed. Brief comments are included on potential applications of this unique family of new materials. 

Modifications of the conduction properties of semiconducting carbon nanotubes by B (p-type) and N ( -type) substitutional doping has also been dis-cussed[3l] and, in addition, electronic modifications by filling the capillaries of the tubes have also been proposed[32]. Exohedral doping of the space between nanotubes in a tubule bundle could provide yet an-... 

Next, let us look at modification of CNTs. There are many approaches to modifying the electronic structure of CNTs oxidation [39], doping (intercalation) [69], filling [70] and substitution by hetero elements like boron and nitrogen atoms [71,72]. There have been few studies on the application of these CNTs but it will be interesting to study applications as well as electronic properties. 

The PES measurements arc performed with reference to the Fermi level of the photoclectron spectrometer, in solid specimens, as dealt with here, by the way the spectroscopy works. Thus, in cases when the Fermi level shifts due to some chemical modifications of the sample, i.e., in the intercalation of graphite or other layered compound [16] or in the doping of conjugated polymers 1171, il is necessary to account for the change in the Fermi energy level before interpreting spec-... 

Application of Solid State Physics to Pyrotechnics Modification of the reactivity of metallic oxides by doping (Refs 56,86 96) may result in safer igniters, initiators and reaction mixts. 

The catalytic system used in the Pacol process is either platinum or platinum/ rhenium-doped aluminum oxide which is partially poisoned with tin or sulfur and alkalinized with an alkali base. The latter modification of the catalyst system hinders the formation of large quantities of diolefins and aromatics. The activities of the UOP in the area of catalyst development led to the documentation of 29 patents between 1970 and 1987 (Table 6). Contact DeH-5, used between 1970 and 1982, already produced good results. The reaction product consisted of about 90% /z-monoolefins. On account of the not inconsiderable content of byproducts (4% diolefins and 3% aromatics) and the relatively short lifetime, the economics of the contact had to be improved. Each diolefin molecule binds in the alkylation two benzene molecules to form di-phenylalkanes or rearranges with the benzene to indane and tetralin derivatives the aromatics, formed during the dehydrogenation, also rearrange to form undesirable byproducts. 

Zinc sulfide, with its wide band gap of 3.66 eV, has been considered as an excellent electroluminescent (EL) material. The electroluminescence of ZnS has been used as a probe for unraveling the energetics at the ZnS/electrolyte interface and for possible application to display devices. Fan and Bard [127] examined the effect of temperature on EL of Al-doped self-activated ZnS single crystals in a persulfate-butyronitrile solution, as well as the time-resolved photoluminescence (PL) of the compound. Further [128], they investigated the PL and EL from single-crystal Mn-doped ZnS (ZnS Mn) centered at 580 nm. The PL was quenched by surface modification with U-treated poly(vinylferrocene). The effect of pH and temperature on the EL of ZnS Mn in aqueous and butyronitrile solutions upon reduction of per-oxydisulfate ion was also studied. EL of polycrystalline chemical vapor deposited (CVD) ZnS doped with Al, Cu-Al, and Mn was also observed with peaks at 430, 475, and 565 nm, respectively. High EL efficiency, comparable to that of singlecrystal ZnS, was found for the doped CVD polycrystalline ZnS. In all cases, the EL efficiency was about 0.2-0.3%. 

Laser ablation of polymer films has been extensively investigated, both for application to their surface modification and thin-film deposition and for elucidation of the mechanism [15]. Dopant-induced laser ablation of polymer films has also been investigated [16]. In this technique ablation is induced by excitation not of the target polymer film itself but of a small amount of the photosensitizer doped in the polymer film. When dye molecules are doped site-selectively into the nanoscale microdomain structures of diblock copolymer films, dopant-induced laser ablation is expected to create a change in the morphology of nanoscale structures on the polymer surface. 

Further modification of the above nanostructures is useful for obtaining new functional materials. Thirdly, we apply the dopant-induced laser ablation technique to site-selectively doped thin diblock copolymer films with spheres (sea-island), cylinders (hole-network), and wormlike structures on the nanoscale [19, 20]. When the dye-doped component parts are ablated away by laser light, the films are modified selectively. Concerning the laser ablation of diblock copolymer films, Lengl et al. carried out the excimer laser ablation of diblock copolymer monolayer films, forming spherical micelles loaded with an Au salt to obtain metallic Au nanodots [21]. They used the laser ablation to remove the polymer matrix. In our experiment, however, the laser ablation is used to remove one component of block copolymers. Thereby, we can expect to obtain new functional materials with novel nanostmctures. 

Site-Selective Modification of the Nanoscale Surface Morphology of Dye-Doped Copolymer Films Using Dopant-Induced Laser Ablation... 

As aforementioned, diblock copolymer films have a wide variety of nanosized microphase separation structures such as spheres, cylinders, and lamellae. As described in the above subsection, photofunctional chromophores were able to be doped site-selectively into the nanoscale microdomain structures of the diblock copolymer films, resulting in nanoscale surface morphological change of the doped films. The further modification of the nanostructures is useful for obtaining new functional materials. Hence, in order to create further surface morphological change of the nanoscale microdomain structures, dopant-induced laser ablation is applied to the site-selectively doped diblock polymer films. 

In supercapacitors, apart from the electrostatic attraction of ions in the electrode/electrolyte interface, which is strongly affected by the electrochemically available surface area, pseudocapacitance effects connected with faradaic reactions take place. Pseudocapacitance may be realized through carbon modification by conducting polymers [4-7], transition metal oxides [8-10] and special doping via the presence of heteroatoms, e.g. oxygen and/or nitrogen [11, 12]. 

The first reports on direct electrochemistry of a redox active protein were published in 1977 by Hill [49] and Kuwana [50], They independently reported that cytochrome c (cyt c) exhibited virtually reversible electrochemistry on gold and tin doped indium oxide (ITO) electrodes as revealed by cyclic voltammetry, respectively. Unlike using specific promoters to realize direct electrochemistry of protein in the earlier studies, recently a novel approach that only employed specific modifications of the electrode surface without promoters was developed. From then on, achieving reversible, direct electron transfer between redox proteins and electrodes without using any mediators and promoters had made great accomplishments. 

There are a number of ways to introduce dopants into an EC-ALE deposit. For instance, they can be introduced homogeneously throughout the deposit, or delta doped into the structure. For a relatively homogeneous distribution, low concentrations of oxidized precursors can be incorporated into the reactant solutions. By using very low concentrations, the amounts incorporated in each atomic layer will be limited. The dopant can also be incorporated in its own cycle step. Again, a low concentration would be used so that some fraction of an atomic layer is introduced each cycle. Alternatively, a delta doping scheme can be constructed where a fraction of an atomic layer of dopant is deposited every set number of cycles. All these scenarios involve only a simple modification of the EC-ALE program. 

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