Semiconductors diamond

Handbook of Chemical Vapor Deposition 8.2 Advantages of Semiconductor Diamond... 

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... 

Owing to its extraordinary chemical stability, semiconductor diamond undoubtedly offers serious competition to other electrode materials. However, unlike other carbonaceous materials (e.g. graphite, glassy carbon, etc.), which gained a wide application in electrochemistry, diamond became an object of electrochemical investigation only as late as the decade of the 1990s. Until then, there was a serious handicap to such an investigation. First, diamond was an extremely rare, hard-to-access material. Second, diamond as such is a dielectric hence, it cannot be used as electrode. 

In this section, unlike the previous one, we deal with less heavily doped, semiconductor diamond. Quantitative studies of reaction kinetics have been performed in Fe(CN)63 -/4, quinone/hydroquinone (recall that this is an inner-sphere reaction), and Ce3+/4+ systems [94, 104, 110]. Potentiodynamic curves recorded in solutions containing only one (either reduced or oxidized) component of a redox system are shown on Figs. 22a and b the dependences of anodic and cathodic current peak po-... 

Figure 2.2 Band diagram in a semiconductor, diamond-structured carbon used as an example. In the left-hand drawing, the bottom line refers to the top of the valence band and the top line refers to the bottom of the conduction band [3].

CVD has been a powerful technique in synthesizing film-structured materials (such as metal-oxide semiconductors, diamond-related materials and carbon nanotubes)... 

Wc turn finally to materials that are not direct-gap semiconductors. The conduction bands of semiconductors have an analogy in the conjugation of verbs those encountered oftenesl have the exceptional forms. Let us first consider the four homopolar semiconductors diamond. Si, Gc, and Sn. In the text following... 

The plasma jet can be cooled rapidly prior to impact on the substrate surface by mixing with a cold inert gas fed into an annular fixture. Gaseous boron or phosphorous compounds can be introduced into the gas feed for the deposition of doped semiconductor diamond,... 

The second group of methods evolved from a solid source of hydrocarbon species formed during etching of graphite by hydrogen see Fig. 2. Using this method, homoepitaxial, doped films have been obtained to demonstrate that semiconductor diamond films can be grown from the... 

As described in this chapter progress in semiconductor diamond is likely to verify the possibilities of diamond devices. The applications of diamond for active devices are to be realized the... 

SiC is the only semiconductor compound of subgroup IV elements—silicon and carbon. SiC is a diamond-like semiconductor and is an electronic analogue of an elementary IVB semiconductor diamond, silicon, germanium, and a-tin. 

More precisely, the potential drop in the Helmholtz layer in a redox electrolyte increases with increasing doping. Therefore, the reaction rate reflects the Helmholtz potential drop, rather than the charge carrier concentration. This is the reason why the behavior of semiconductor diamond is far from ideal in particular, no current rectification is typically observed on (rather heavily doped) diamond electrodes, as mentioned above. 

On metal electrodes, the transfer coefficients typically approach 0.5. Generally, the transfer coefficients for redox reactions on moderately doped diamond electrodes are smaller than 0.5 their sum a +p, less than 1. We recall that an ideal semiconductor electrode must demonstrate a rectification effect in particular, on p-type semiconductors, reactions proceeding via the valence band have the transfer coefficients a = 0, P = 1, and thus, a +p = 1 [7]. Actually, the ideal behavior is rarely the case even with single crystal semiconductor materials manufactured by use of advanced technologies ( like germanium, silicon, gallium arsenide, etc.). The departure from the ideal semiconductor behavior is likely to be caused by the fact that the interfacial potential drop appears essentially localized, even in part, in the Helmholtz layer, due, e.g., to a high density of surface states, or the surface states directly participate in the electrochemical reactions. As a result, the transfer coefficients a and p have intermediate values, between those characteristic of semiconductors (O or 1) and metals (-0.5). Semiconductor diamond falls in with this peculiarity. However, for heavily doped electrodes, the redox reactions often proceed as reversible, and the transfer coefficients approach 0.5 ( metaMike behavior). 

Binary alloys - mixtures of two elemental semiconductors (diamond. Si, Ge...)... 

---