Hydrogen porous silicon

Figure 2. Temperature programmed desorption (TPD) for hydrogenated porous silicon.

Koch EC, Clement D (2007) Special materials in pyrotechnics VI. Silicon - an old fuel with new perspectives. Propell Explos Pyrotech 32(3) 205-212 Kovalev D, Timoshenko VY, Kiinzner N, Gross E, Koch F (2001) Strong explosive interaction of hydrogenated porous silicon with oxygen at cryogenic temperatures. Phys Rev Lett 87 68301(1-4)... 

The radical-based functionalization of silicon surfaces is a growing area because of the potential practical applications. Although further knowledge is needed, the scope, limitations, and mechanism of these reachons are sufficiently well understood that they can be used predictably and reliably in the modification of hydrogen-terminated silicon surfaces. The radical chemistry of (TMSlsSiH has frequently served as a model in reactions of both hydrogen-terminated porous and flat silicon surfaces. We trust that the survey presented here will serve as a platform to expand silicon radical chemistry with new and exciting discoveries. 

NHE OCP ONO OPS PCD PDS PL PLE PMMA PP PP PS PSG PSL PTFE PVC PVDF normal hydrogen electrode (= SHE) open circuit potential oxide-nitride-oxide dielectric oxidized porous silicon photoconductive decay photothermal displacement spectroscopy photoluminescence photoluminescence excitation spectroscopy polymethyl methacrylate passivation potential polypropylene porous silicon phosphosilicate glass porous silicon layer polytetrafluoroethylene polyvinyl chloride polyvinylidene fluoride... 

Study of porous silicon nanostructures as hydrogen reservoirs, V. Lysenko, F. Bidault, S. Alekeev, V. Zaitsev, D. Barbier, C. Turpin, F. Geobaldo, P. Rivolo, D. Garrone, J. Phys. Chem. B 2005, 109, p. 19711-19718. 

Another way to use silicon wafers as DLs was presented by Meyers and Maynard [77]. They developed a micro-PEMFC based on a bilayer design in which both the anode and the cathode current collectors were made out of conductive silicon wafers. Each of fhese componenfs had a series of microchannels formed on one of their surfaces, allowing fhe hydrogen and oxygen to flow through them. Before the charmels were machined, a layer of porous silicon was formed on top of the Si wafers and fhen fhe silicon material beneath the porous layer was electropolished away to form fhe channels. After the wafers were machined, the CEs were added to the surfaces. In this cell, the actual diffusion layers were the porous silicon layers located on top of the channels because they let the gases diffuse fhrough fhem toward the active sites near the membrane. 

Figure 8.3 Hydrogen-terminated Si(l 11), Si(lOO) and porous silicon surfaces.

This chapter will focus on organic/silicon interfaces formed via solution phase reactions using hydrogen-terminated crystalline silicon surfaces as a starting point. While some of the surface chemistry issues have been reviewed previously [7,8], more recent developments will be emphasized here. We will not discuss the considerable literature of reactions with porous silicon [8], or studies of molecules reacting with clean silicon surfaces under ultrahigh vacuum (UHV) conditions [9-11] which have been reviewed elsewhere. 

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). 

Internal reflection infrared spectra measured in situ during etching of silicon in HF solutions exhibit characteristic Si - H modes, although the Si - H spectrum is broad because of interaction of the surface Si-H groups with the electrolyte. No electrochemical or chemical intermediate species have been detected [112]. Infrared spectra of porous silicon layers after drying reveal characteristic Si-H and Si-H2 peaks similar to the spectra obtained for hydrogen on Si(lOO) 2x1 surfaces [112]. 

Y. Ogata, H. Niki, T. Satsuo, T. Sakka, and M. Iwasaki, Hydrogen in porous silicon Vibrational analysis of SiHx species, J. Electrochem. Soc. 142, 195, 1995. 

Kelly, E. S. Kooij, and D. Vanmaekelbergh, Generation and quenching of luminescence in n-type porous silicon/solution diodes Role of adsorbed hydrogen, Langmuir 15, 3666, 1999. 

Y. Kato, T. Ito, and A. Hiraki, Initial oxidation process of anodized porous silicon with hydrogen atoms chemisorbed on the inner surface, Jpn. J. Appl. Phys. 27, L1406, 1988. 

P. Allongue, C. H. de Villeneuve, M. C. Bernard, J. E. Peou, A. Boutry-Forveille, and C. Levy-Clement, Relationship between porous silicon formation and hydrogen incorporation, Thin Solid Films 297, 1, 1997. 

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