Surface hydrogen-terminated

On such very useful hydrogen-terminated surfaces, immobilization of a,(B-alkenethiol-stabilized gold nanoparticles was carried out. The thermal hydrosilylation was selected for this immobilization. Under dry nitrogen... 

The formation of a chemical oxide in pure DI water was found to depend critically on the DOC of the water [Gr3, Mol, Li9]. In DI water of very low DOC (<0.004 ppm), no native oxide forms. Furthermore the reverse reaction is observed for elevated temperatures (80 °C) and long etching times (60 min) thin native or chemical oxides are removed and a hydrogen-terminated surface is established [Wa2]. 

Scheme 13.1 Reaction of a hydrogen terminated surface with an alkene to generate surface mono-layers (a) monolayer formation by reaction of silicon with H2C=CH(CH2)90Ph(C6H40Me)2, (b, c) monolayer derivatisation to give a surface layer of tethered magnetic TiW5 polyoxometalate clusters.4...

An alternate route to formation of alkyl monolayers is via Lewis acid catalyzed reactions of alkenes with the hydrogen terminated surface. In this approach, a catalyst such as ethyl aluminum dichloride is used to mediate the hydrosilylation reaction of an alkene (or alkyne), resulting in the same type of product as in the case of the photochemical or thermal reactions. This type of reaction is well known based on molecular organosilane chemistry and has also been used successfully to alkylate porous silicon [31]. Although this route has been shown to work on H/Si(lll), the resulting monolayers are found to have lower coverages than those achieved using the photochemical or thermal approach [29], Another concern with this approach is the possibility of trace metal residues from the catalyst that could adversely affect the electronic properties of these surfaces (even when present at levels below the detection limit of most common surface analysis techniques). 

We are led to the conclusion that it is not sufficient to consider only dangling bonds (i.e., chemisorption sites) and hydrogen-terminated surface sites. An extended model is proposed which is described in detail in [28,45]. We merely summarize the main aspects here the incorporation of the impinging... 

The formation of ultraclean and oxide-free surfaces is important in the fabrication of high-quality electronic devices. In some cases stabilization of the surface is also important for example, the Si(lll) surface is unstable in vacuum and reconstructs to a lower-energy configuration, e.g. Si(lll) 7x7. In the last few years, a variety of experimental techniques have been used to investigate the nature of the interaction between silicon surfaces and HF solutions and, in particular, the structure and properties of the hydrogen-terminated surface. 

Molecular orbital calculations for chemical reactions involving the insertion of HF molecules into Si-Si backbonds support this hypothesis [38], as shown in Tkble 3. From these calculations it can be seen that the Si-Si backbonds for the hydrogen-terminated surface exhibit a 1.6 eV activation barrier and hence are rela-... 

In summary, oxide layers on silicon surfaces are chemically dissolved in HF leading to the formation of an atomically rough hydrogen-terminated surface. At (111) surfaces, relatively large domains of ideally terminated Si(lll) H (1x1) can be formed by subsequent immersion in buffered HF of pH 8-9. The smoothening process is controlled by the rate of step recession at the surface. 

In terms of science, it is expected that diamond still has some new properties that have never been exploited yet. Since the establishment of diamond CVD technology, the controlled doping for p- and n-type semiconductors, the presence of the ultrathin conducting layers of hydrogen-terminated surface, the negative... 

The surface of silicon can be hydrophilic or hydrophobic depending on the surface condition. It has been reported that a hydrophilic surface is characterized by OH groups and a hydrophobic surface is covered with Si-H, Si-CH , or Si-F groups. Thus, a hydrogen-terminated surface is hydrophobic whereas an oxide- or hydroxide-covered surface, which tends to be terminated by OH, is, in general, hydrophilic. A surface covered with a substantial amount of carbon bonded to oxygen is hydrophobic. 

FTIR has been used to study the sihcon/electrolyte interface. The formation of porous silicon on n-Si during photoetching in fluoride media can readily be followed since the hydrogen-terminated surface is identified by the Si-H stretch bands centred around 2100 cm (Peter et ah, 1989 Peter et ah, 1990a). Similarly, the transition from a hydrogen-terminated to an oxide-covered surface during electropolishing has been followed by in-situ infrared spectroscopy (da Fonseca et al, 1996 and 1997). 

S-band hydrogen-terminated surface From near-infiared to blue 400-1,300 A few ns to 150 ps Yes Quantum confinement in Si nanocrystals indirect bandgap transitions blueshift upon size reduction (Cullis et al. 1997 Bisi et al. 2000 Wolkin et al. 1999)... 

Both a 1x1 phase obtained by polishing and a 2x2/2xl phase obtained by annealing to above 1000 C were observed by LEED. (LEED cannot distinguish between a true 2x2 or disordered domains of 2x1 for this surface the similarity of the angle-resolved photoemission to that of Si and Ge suggests the latter.) No surface states were observed in the gap for the 1x1 diamond surface. However, recent experiments have shown that this is a hydrogen-terminated surface. The 2x2/2xl surface, on the other hand, is believed... 

Nitrogen and boron are the only elements that significantly affect the bulk electrical conductivity of diamond in addition, a hydrogen-terminated surface gives rise to p-type conduction (24,25). 

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