Hydrogenation diamond films

Due to the wide bandgap, the conduction band of diamond approximates the vacuum level. Consequently, electrons excited into the conduction band may leave the diamond s surface as there is no significant potential difference between conduction band and vacuum level. In hydrogenated diamond films, the conduction band is even observed to exceed the vacuum level, resulting in a negative electron affinity of the respective film. This causes the emission of excited electrons from the film to occur all the easier. 

Figure 6.45 Mechanism for the photochemical reaction of hydrogenated diamond films with co-vinyl species rendered suitable for further reaction by carrying terminal functional groups.

Figure 6.46 Photochemical reaction of hydrogenated diamond films with 1-chloro-5-hexene, followed by a substitution of the terminal chlorine atoms.

Hoffman, A., A. Laikhtman, S. Ustaze et al. 2001. Dissociative electron attachment and dipolar dissociation of H electron stimulated desorption from hydrogenated diamond films. Phys Rev B Condens Matter 63 045401. 

FIGURE 11.1 SEM images of (a) a diamond film grown with methane, hydrogen, and 0.2% PH3, showing (100) square facets and (b) a diamond film grown at lower substrate temperature—now the crystals are predominantly (7 iij triangular facetted. (Courtesy of Dr. P.D. May and Professor M.N.R.Ashfold, Bristol University.)... 

M. Murayama and K. Uchida. Synthesis of Uniform Diamond Films by Flat Flame Combustion of Acetylene/Hydrogen/Oxygen Mixtures. Combust. Flame, 91 239-245,1992. 

Hard amorphous carbon films may either be fully amorphous or contain tiny diamond crystallites. Hydrogen-free films may be deposited on surfaces from graphite by laser ablation or ion sputtering. Hydrogen-containing films are also possible. 

Figure 45 Auger electron spectra (AES) of a hydrogen-terminated boron-doped diamond film supported on a diamond made (see text for details). (From Ref. 67.)...

Furthermore, it has been proved that direct oxidation can happen on the diamond film electrode before the oxygen gas evolution potential (Zhi et al. 2003). Direct oxidation takes place, accompanying with the adsorption of chemical molecules on the diamond electrode surface. An as-grown diamond film with high hydrogen coverage is inert to adsorption of polar molecules (Vinokur, Miller et al. 1996 Yano... 

Fig. 3.8 Typical cyclic voltammogram of boron doped diamond film electrode. The result was tested in 0.5 M H2SO4 solution at 0.1 V s 1 scan rate. The standard hydrogen gas and oxygen gas evolution potentials were marked with E t and Eq2, respectively (after Guo and Chen 2007b)...

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