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Physical properties porous silicon

Prokes, S.M. (1996) Porous silicon nanostructures, in Nanomaterials Synthesis, Properties and Applications, eds. Edelstein, A.S. and Cammarata, R.C. (Institute of Physics Publishing, Bristol and Philadelphia) p. 439. [Pg.421]

As a result of its unique chemical and physical properties, silica gel is probably the most important single substance involved in liquid chromatography today. Without silica gel, it is doubtful whether HPLC could have evolved at all. Silica gel is an amorphous, highly porous, partially hydrated form of silica which is a substance made from the two most abundant elements in the earth s crust, silicon and oxygen. Silica, from which silica gel is manufactured, occurs naturally, either in conjunction with metal oxides in the form of silicates, such as clay or shale, or as free silica in the form of quartz, cristobalite or tridymite crystals. Quartz is sometimes found clear and colorless, but more often in an opaque form, frequently colored... [Pg.55]

Non-Debye dielectric relaxation was also observed in porous silicon (PS) [25,160,161], PS has attracted much attention recently, mainly due to its interesting optical and electro-optical properties that can be utilized for device applications [164,165], So far, most of the activity in this field has focused on the intense visible photoluminescence (PL) from nano-PS and the underlying physical mechanism that is responsible for the generation of light. In addition, transport and dielectric relaxation phenomena in PS have also attracted... [Pg.41]

A. Grosman, M. Chamarro, V. Morazzani, C. Ortega, S. Rigo, J. Siejka, and H. J. von Bardeleben, Study of anodic oxidation of porous silicon Relation between growth and physical properties, /. Lumin. 57, 13, 1993. [Pg.485]

Beyond the motivation to fabricate working systems from functionalized porous silicon, there is also more fundamental interest in the reactions of its surfaces. Because the vast surface of nanocrystalline silicon contains a large fraction of the total atoms, the composition and environment of the silicon interface are believed to affect greatly the physical, chemical, and electronic properties of the material. In particular, functionalization of porous silicon with certain organic groups is known to diminish photoluminescence [27] however, the mechanism of quenching has... [Pg.523]

Evolution of reflectivity signals over time has been used to temporally resolve the constituents of a binary vapor mixture [102]. Since the studied solvents (ethanol and acetone) have identical refractive indices, changes in the optical reflectance of porous silicon exposed to these vapors were shown to depend upon the rates of diffusion and adsorption of these species into the material. Time-resolved refrac-tometry revealed that an equimolar mixture of acetone and ethanol vapors exhibited markedly different condensation within porous silicon than did the pure mixture constituents (figure 16.14). This method is comparable to gas chromatography in that the vapor mixture interacts with the matrix in a manner dependent upon the physical properties of its components, but the porous silicon device... [Pg.535]

Porous silicon (PS) is one of the nanoscale modifications of silicon. There are various approaches to PS producing that are now in use. The technique most generally employed today is known as wet anodization of a crystalline silicon. With this technique, yield parameters of porous material (porosity, pore size and shape, interpore distance) may be readily varied by anodization regimes. However, it is well known the problem of the PS stability influencing the physical properties of the PS layers. P S instability is c onditioned b y very large specific surface area of the porous material. [Pg.488]

Clusters of small and intermediate size play an important role in the explanation of the chemical and physical properties of matter on the way from molecules to solids. The great interest in silicon clusters stems from the importance of silicon in solid-state physics and from the photoluminescence properties of porous silicon. In Chapter 20, A. F. Sax presents theoretical models to describe bare and hydrogenated small silicon clusters and discusses... [Pg.116]

The study of small and intermediate-sized clusters has become an important research field because of the role clusters play in the explanation of the chemical and physical properties of matter on the way from molecules to solids/ Depending on their size, clusters can show reactivity and optical properties very different from those of molecules or solids. The great interest in silicon clusters stems mainly from the importance of silicon in microelectronics, but is also due in part to the photoluminescence properties of silicon clusters, which show some resemblance to the bright photoluminescence of porous silicon. Silicon clusters are mainly produced in silicon-containing plasma as used in chemical vapor deposition processes. In these processes, gas-phase nucleation can lead to amorphous silicon films of poor quality and should be avoided.On the other hand, controlled production of silicon clusters seems very suitable for the fabrication of nanostructured materials with a fine control on their structure, morphological, and functional properties. ... [Pg.269]

Naderi, N., Hashim, M. R. and Amran, T. S. T. Enhanced physical properties of porous silicon for improved hydrogen gas sensing , (2012) Superlattice. Microsl 51,626-636. [Pg.428]

Layered crystalline titanates (CT) [Anthony and Dosch, U.S. Patent 5 177 045 (1993)] are pillared with tetraethyl orthosilicate, 3-aminopropyltrimethoxysilane, and aluminum(III) acetylacetonate to prepare porous and high surface area supports for sulfided NiMo catalyst. Tetraethyl orthosilicate or aluminum(III) acetylacetonate intercalated CT are prepared by stepwise intercalation. First, the basal distance is increased by n-alkylammonium ions prior to intercalation with inorganic compounds. However, an aqueous solution of 3-aminopropyltrimethoxysilane can directly pillar CT without first swelling the titanate with n-alkylamine. The catalytic activities for hydrogenation of pyrene of sulfided NiMo supported silica or alumina pillared CT are higher than those of commercial catalysts (Shell324 and AmocatlC). The silicon and aluminum contents of the pillared CT, used as supports, have considerable effects on the catalytic activities and physical properties of the supports. [Pg.391]

In this review we detail how the color of mesoporous silicon can be tuned, like many other properties (see handbook chapter Tunable Properties of Porous Silicon ). This has been achieved by both control of the physical structure of silicon at the nanoscale and chemical means. The physical color of porous silicon films, membrane flakes, and photonic crystals is much more easily tuned than those of milled microparticle powders. The latter display various shades of brown, rather than the gray of solid silicon, and this has to date been an obstacle for applications in certain high-volume consumer products. [Pg.100]

The future development of porous silicon (PS)-based optoelectronic devices depends on a proper understanding of electrical transport properties of the PS material. Electrical transport in PS is influenced not only by each step of processing and fabrication methods but also by the properties of the initial base substrate. This chapter endeavors to chronologically document how the knowledge base on the nature of carrier transport in PS and the factors governing the electrical properties has evolved over the past years. The topics covered include the proposed electrical transport models including those based on effective medium theories, studies on contacts, studies on physical factors influencing electrical transport, anisotropy in electrical transport, and attempts to classify the PS material. [Pg.144]

Gao L, Mbonu N, Cao L, Gao D (2008) Label-free colorimetric detection of gelatinases on nanoporous silicon photonic films. Anal Chem 80 1468 Ghosh S, Hong K, Lee C (2002) Structural and physical properties of thin copper films deposited on porous silicon. Mater Sci Eng B96 53... [Pg.211]

Steiner P, Kozlowski F, Wielunski M et al (1994) Enhanced blue-light emission from an indium-treated porous sihcon device. Jpn J Appl Phys 33 6075-6077 Stievenard D, Deresmes D (1995) Are electrical properties of an aluminium-porous silicon junction governed by dangling bonds Appl Phys Lett 67 1570-1572 Sze SM (1985) Semiconductor devices physics and technology. Wiley, New York Tsai C, Li KH, Sarathi J et al (1991) Thermal treatment studies of the photoluminescence intensity of porous silicon. Appl Phys Lett 59 2814-2816... [Pg.368]

The physical properties of a porous silicon sample can vary depending on, for example, the degree of lateral variation in layer thickness and/or porosity, the interface roughness between porous layers or at the layer/substrate boundary, and any vertical porosity gradation. As mentioned previously, careful design of the anodization equipment can minimize most sources of inhomogeneity. [Pg.564]


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See also in sourсe #XX -- [ Pg.437 ]




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