Gold metal electrode, deposition

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. 

A schematic view of the cold cathode fabrication process is shown in Fig. 10.18. The cold cathode is fabricated by low pressure chemical vapor deposition (LPCVD) of 1.5 pm of non-doped polysilicon on a silicon wafer or a metallized glass substrate. The topmost micrometer of polysilicon is then anodized (10 mA cnT2, 30 s) in ethanoic HF under illumination. This results in a porous layer with inclusions of larger silicon crystallites, due to faster pore formation along grain boundaries. After anodization the porous layer is oxidized (700 °C, 60 min) and a semi-transparent (10 nm) gold film is deposited as a top electrode. 

UPD of various metals on different gold surfaces is one of the most intensively studied subjects. Abruna and coworkers have reviewed [380] the UPD deposition at single-crystal surfaces of Au, Pt, Ag, and other materials. More recently, Mag-nussen [381] has described ordered anion adlayers on metal electrode surface, which can affect the UPD process. 

In another attempt to resolve the puzzle around the DNA conduction properties, de Pablo et al. [58] apphed a different technique to measure single A-DNA molecules on the surface in ambient conditions. They deposited many DNA molecules on mica, covered some of them partly with gold, and contacted the other end of one of the molecules (>70 nm from the electrode) with a metal AFM tip (see Fig. 7). No current was observed in this measurement. Furthermore, they covered 1,000 parallel molecules on both ends with metal electrodes ( 2 /zm apart) and again no current was observed. Yet another negative result, pubhshed in 2002, was obtained in a similar experiment by Zhang et al. [33] who stretched many single DNA molecules in parallel between metal electrodes and measured no current upon voltage application. Both results [33, 58] were consistent with the Storm et al. experiment [60]. 

More than at mercury, it makes a difference whether the electrode is inert or not. In the first case, the electrode reaction is of the type Fe3+/ Fe2+ etc. and the modelling of processes is the same as with mercury. However, if the electrode reaction is of the type Zn2+/Zn, e.g. at a gold electrode, at least the electrode surface will be modified by the deposited zinc, Frequently, it is observed that the first monolayer of the foreign metal is deposited at a potential substantially positive to its standard potential. This phenomenon is named underpotential deposition and bears some resemblance to an electrode reaction that involves adsorption of the reacting species (see Sect. 6). 

Our clear recommendation is to have a critical look at any ionic liquid delivered by any of the suppliers. Glassy carbon is a bad substrate to probe inorganic impurities in ionic liquids. In our experience noble metal electrodes like gold or platinum are better suited to detect low amounts of impurities. We have further examples in Clausthal where we saw clearly, with the in situ STM, metal deposition in apparently ultrapure liquids. In several liquids we found, with XPS and/or EDX, considerable amounts of potassium. Upon our insistence, the supplier finally told us that the synthesis route had been changed. For technical experiments such low amounts of... 

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... 

Noble metal electrodes include metals whose redox couple M/Mz+ is not involved in direct electrochemical reactions in all nonaqueous systems of interest. Typical examples that are the most important practically are gold and platinum. It should be emphasized, however, that there are some electrochemical reactions which are specific to these metals, such as underpotential deposition of lithium (which depends on the host metal) [45], Metal oxide/hydroxide formation can occur, but, in any event, these are surface reactions on a small scale (submonolayer -> a few monolayers at the most [6]). 

As the pen is gently rubbed on the object to be plated, a thin film of metal is deposited on the surface. If you plate the electrode surfaces with gold, plate them with nickel first. If you simply plate the copper with gold, the gold is absorbed or migrates into the copper over a short period of time. To prevent this, a nickel plate base is necessary. Plating kits... 

If you dip a metal rod into a water solution of its ions, the atoms may lose electrons, form ions, and go into the solution, or ions in the solution may gain electrons from the metal rod, form more metal, and deposit on the rod. Each type of atom or ion has different amounts of positive and negative charges around it, and it only seems reasonable that they should either attract electrons or donate electrons to electrodes under different conditions. You want to take advantage of this difference in attraction to electrodes to separate various systems. For example, sodium, will immediately give up an electron and go into solution as a sodium ion. Gold will not do this very readily at all. This is why you can pan for gold in a river, but you don t pan for sodium. 

The electrocapillary curve of a solid metal electrode is more difficult to measure than that of a liquid electrode, because of problems of surface cleanliness. The most widely used approach has been the bending-beam method, which was originally developed by Fredlein et al. [28] using large samples. More recently Raiteri and Butt [29] have used gold electrodes deposited on an AFM cantilever to record electrocapillary curves. 

Several sample-handling techniques are employed for SERS, In one technique, colloidal silver or gold particles are suspended in a dilute solution (usually aqueous) of the sample. The solution is then held or flowed through a narrow glass tube while it is excited by a laser beam. In another method, a thin film of colloidal metal panicles is deposited on a glass slide and a drop or two of the sample solulion spotted on the film. The Raman spectrum is then obtained in the usual manner. Alternatively, the satnple may be deposited electrolytically on a roughened metal electrode, which is then removed from the solulion and exposed to the laser excitation source. 

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