Aluminum metal electrode, deposition

Accordion polymers—Continued orientational and chemical stability, 139 synthesis by Knoevenagel condensation polymerization, 135-136 waveguide construction, 139-140 Aluminum metal electrode, deposition on polymer in LED, 411,412/ Aromatic amine-containing polymers dye-dispersed poly(N-vinylcarbazole), 387, 390-393... 

The temperature sensor in the membrane center is made of polysilicon with a nominal resistance of 10 kQ. An additional reference resistor is needed for the control circuitry (Sect. 5.1). For the resistance measurement of the sensitive layer, platinum electrodes are deposited on top of the CMOS aluminum metallization in order to establish good electrical contact to the sensitive metal oxide. 

Such a cell with zinc and aluminum electrodes would have an overall potential of +0.90 volts, with aluminum being dissolved and zinc metal being deposited out of solution. 

Aluminum, a highly electropositive metal similar to the aUcaline earth metals, can be useful in deposition of low work function cathode metal electrodes in OLEDs and OELDs, and is preferred for many electronics applications because of its low cost and high conductivity, although it is somewhat prone to electro migration [8, 65]. Since A1 is an important metal for device applications its deposition on SAMs has been extensively studied [20, 21, 23, 32, 33,41, 50, 65-69]. The critical problem for Al, however, is its facility in penetration along with filament growth. 

Fig. 5.37. (a) I/V characteristics of typical MDMO-PPV/PCBM solar cells with a LiF/A1 electrode of various LiF thicknesses ( 3 A, 6 A, 12 A) compared to the performance of a MDMO-PPV/PCBM solar cell with a pristine A1 electrode ( ). (b) and (c) are box plots with the statistics of the FF and Voc from 6 separate solar cells. LiF or SiOx were thermally deposited at a rate of 1-2 A/min from a tungsten boat in a vacuum system with a base pressure of 10-4 Pa. We emphasize that, for thickness values of the order of 1 nm, LiF/SiOx does not form a continuous, fully covering layer, but instead consists of island clusters on the surface of the photoactive layer. Slow evaporation conditions are essential for more homogenous distribution of the LiF on the organic surface. The nominal thickness values given here represent an average value across the surface of the substrate. The metal electrode (either aluminum or gold) was thermally deposited with a thickness of 80 nm... 

Additional work on dielectrics includes deposition of silica, PABS (lead aluminum boron silicates), PLZT (lead lanthanum zirconium titanate) and BST (barium strontium titanate) on Si-Ti-Pt wafers (Figure 2). The wafer specimens were patterned with metal electrodes and electronic properties were characterized. 

Films of oxides can be produced by anodization of metal electrodes. For example, AI2O3 forms on an aluminum anode immersed in a solution of H3PO4. The thickness of the film can be controlled by the applied potential and the time of anodization. Such a film can be used as a support for other materials, such as poly(vinylpyridine) (PVP). Oxide films of other metals, such as Ti, W, and Ta, can be produced in a similar way. Oxide films can also be produced by CVD, vacuum evaporation and sputtering, and deposition from colloidal solution. Related inorganic films are those of polyoxometallates (iso- and heteropolyacids and their salts) (20). For example, the heteropolyanion P2W17M0O62K6 shows a number of reduction waves at a glassy carbon electrode. A wide variety of metallic polyanionic species (e.g., of W, Mo, V) exist and have a rich chemistry. Films of such materials are interesting for their electrocatalytic possibilities. 

The dielectric materials used in power capacitors include paper, polypropylene, and mixed vacuums impregnated with mineral or synthetic oil. The most reliable dielectric material is polypropylene. The metal electrodes can be aluminum foils or thin metal films deposited onto the surfaces of the dielectrics. The reliabilities and lifetimes of power capacitors are always concerns because of the possibility of overheating. 

In the many reports on photoelectron spectroscopy, studies on the interface formation between PPVs and metals, focus mainly on the two most commonly used top electrode metals in polymer light emitting device structures, namely aluminum [55-62] and calcium [62-67]. Other metals studied include chromium [55, 68], gold [69], nickel [69], sodium [70, 71], and rubidium [72], For the cases of nickel, gold, and chromium deposited on top of the polymer surfaces, interactions with the polymers are reported [55, 68]. In the case of the interface between PPV on top of metallic chromium, however, no interaction with the polymer was detected [55]. The results concerning the interaction between chromium and PPV indicates two different effects, namely the polymer-on-metal versus the metal-on-polymer interface formation. Next, the PPV interface formation with aluminum and calcium will be discussed in more detail. 

The metallic impurities present in an impure metal can be broadly divided into two groups those nobler (less electronegative) and those less noble or baser (more electronegative) as compared to the metal to be purified. Purification with respect to these two classes of impurities occurs due to the chemical and the electrochemical reactions that take place at the anode and at the cathode. At the anode, the impurities which are baser than the metal to be purified would go into solution by chemical displacement and by electrochemical reactions whereas the nobler impurities would remain behind as sludges. At the cathode, the baser impurities would not get electrolytically deposited because of the unfavorable electrode potential and the concentration of these impurities would build up in the electrolyte. If, however, the baser impurities enter the cell via the electrolyte or from the construction materials of the cell, there would be no accumulation or build up because these would readily co-deposit at the cathode and contaminate the metal. It is for this reason that it is extremely important to select the electrolyte and the construction materials of the cell carefully. In actual practice, some of the baser impurities do get transferred to the cathode due to chemical reactions. As an example, let the case of the electrorefining of vanadium in a molten electrolyte composed of sodium chloride-potassium chloride-vanadium dichloride be considered. Aluminum and iron are typically considered as baser and nobler impurities in the metal. When the impure metal is brought into contact with the molten electrolyte, the following reaction occurs... 

The electrochemistry of Ti2+ in 66.7 m/o AlCl3-NaCl has been investigated wherein the electroactive Ti2+ was prepared by the oxidation of Ti metal with liquid A1C13 [176, 185] and by the electrochemical dissolution of titanium metal [120, 177], The authors of both studies concluded that Ti2+ may be oxidized stepwise to Ti3+ and Ti4+ and that both processes are reversible at platinum and tungsten electrodes. However, anomalous voltammetric behavior at high Ti2+ concentrations (greater than 50 mmol L ) suggests the formation of polymeric Ti2+ species in the melt. The reduction of Ti2+ to the metal was not observed at potentials more positive than that required for aluminum deposition. 

Nearly pure cadmium sponge is precipitated by the addition of high-purity. lead-free zinc dust. The cadmium sponge then is redigested in spent cadmium electrolyte, alter which the cadmium is deposited by electrolysis onto aluminum cathodes. The metal is then stopped from the electrodes, melted, and cast into various shapes. Reactions which occur during the electrolytic process are (Roasting) ZnS +1,0 — — ZnO +... 

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