Metal-like diamond

Kinetics of Outer-Sphere Reactions on Metal-Like Diamond Electrodes. 235... 

Owing to its extraordinary chemical stability, diamond is a prospective electrode material for use in theoretical and applied electrochemistry. In this work studies performed during the last decade on boron-doped diamond electrochemistry are reviewed. Depending on the doping level, diamond exhibits properties either of a superwide-gap semiconductor or a semimetal. In the first case, electrochemical, photoelectrochemical and impedance-spectroscopy studies make the determination of properties of the semiconductor diamond possible. Among them are the resistivity, the acceptor concentration, the minority carrier diffusion length, the flat-band potential, electron phototransition energies, etc. In the second case, the metal-like diamond appears to be a corrosion-stable electrode that is efficient in the electrosyntheses (e.g., in the electroreduction of hard to reduce compounds) and electroanalysis. Kinetic characteristics of many outer-sphere... 

Dimigen, H. and Klages, C. R, Microstructure and Wear Behavior of Metal-containing Diamond-like Coatings, Surf. Coat. Technol, Vol. A9,1991,pp. 543-547. 

Refined X-ray methods have also been applied to other types of crystal [7—9). In some metals, for example, the inter-ionic electron minimum density corresponds to some few electrons spread over the lattice (2 for Mg, 3 for A1 for example). And in covalent crystals like diamond there are non-spherical interatomic concentrations corresponding to the chemists covalent bonds, although such effects are small even for germanium (7). 

Moderately doped diamond demonstrates almost ideal semiconductor behavior in inert background electrolytes (linear Mott -Schottky plots, photoelectrochemical properties (see below), etc.), which provides evidence for band edge pinning at the semiconductor surface. By comparison in redox electrolytes, a metal-like behavior is observed with the band edges unpinned at the surface. This phenomenon, although not yet fully understood, has been observed with numerous semiconductor electrodes (e.g. silicon, gallium arsenide, and others) [113], It must be associated with chemical interaction between semiconductor material and redox system, which results in a large and variable Helmholtz potential drop. 

For metals and ionic solids, in which atoms interact only by omni-directional primary bonds, it is clear that S will be the fracture energy of sudi bonds normalised to unit area. For co-valently bonded solids, like diamond, the secondary bonding energies are negligible with respect to the primary bond strengths so that S will be given directly by the latter - again normalised to unit area. 

Note that diamond and a metal like copper have quite dissimilar structures, although both are based on a face-centered cubic Bravais lattice. To distinguish between these two, the terms diamond cubic and face-centered cubic are usually used. The industrially important semiconductors, silicon and germanium, have the diamond cubic structure. 

Zirconium is a lustrous, gray-white metal. Because of its high resistance to corrosion and its low cross section for neutron absorption, it is often used in nuclear reactors. It can also be processed to produce gems that look like diamonds and are used in jewelry. 

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