Oxide films flat surfaces

One approach to the production of high-performance dielectrics relies on the use of mixed-metal, multiple-component oxides. These oxides provide convenient means for controlling the dielectric-constant breakdown-field product through incorporation of components that specifically contribute to performance via dielectric constant or breakdown. At the same time, the mixed materials can inhibit crystallization, resulting in deposition of amorphous films with extremely flat surfaces. Common candidates, base oxides for tuning these properties, are listed in Table 4.1. 

The surface was actually a film of native aluminum oxide it did not adsorb pyridine but did adsorb chloroform showing the oxide to have no acid sites, but basic sites. Treatment of the aluminum oxide with aqueous carbonate solutions clearly enhanced the basicity, as evidenced by stronger adsorption of chloroform. By observing the temperature coefficient of adsorption isotherms with ellipsometry one can actually determine heats of adsorption on a square centimeter of flat surface. 

In comparison to most other methods in surface science, STM offers two important advantages (1) it provides local information on the atomic scale and (2) it does so in situ [50]. As STM operates best on flat surfaces, applications of the technique in catalysis relate to models for catalysts, with the emphasis on metal single crystals. Several reviews have provided excellent overviews of the possibilities [51-54], and many studies of particles on model supports have been reported, such as graphite-supported Pt [55] and Pd [56] model catalysts. In the latter case, Humbert et al. [56] were able to recognize surface facets with (111) structure on palladium particles of 1.5 nm diameter, on an STM image taken in air. The use of ultra-thin oxide films, such as AI2O3 on a NiAl alloy, has enabled STM studies of oxide-supported metal particles to be performed, as reviewed by Freund [57]. 

The high surface area of the mesoporous metal oxide film is critical to efficient device performance as it allows strong absorption of solar irradiation to be achieved by only a monolayer of adsorbed sensitiser dye. Whereas a dye monolayer absorbed on a flat interface exhibits only negligible light absorption (the optical absorption... 

The application of photocurrent spectroscopy is not restricted to bulk semiconductors and insulator electrodes. The anodic oxidation of many metal electrodes produces surface films that are insulators or semiconductors, and in spite of the fact that these surface films are often very thin, their characterisation by photocurrent spectroscopy poses few experimental difficulties since photocurrents as small as 10 10 A can be measured by conventional lock-in methods. The instrumentation required for photocurrent spectroscopy is relatively modest and the technique is undemanding in terms of the degree of optical perfection of the electrode surface. Consequently, there seems to be considerable scope for the application of this type of spectroscopy to electrochemical problems such as corrosion, for example, where surface roughening may rule out methods that require an optically flat surface. 

Schematic representation of a metal-arch capacitance transducer according to Jones et al. [245]. This capacitance transducer is of the variable-area electrode type. A tantalum/tantalum oxide film structure is deposited onto a flat glass substrate to obtain a suitably flat surface for contact with a flexible electrode which may be a thin metal foil possibly deposited in the shape of a dome or an arch...

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