SYNTHESIS OF POROUS SILICON

To prepare the sample for TEM analysis, put a drop of the chloroform suspension on a TEM grid and allow the solvent to evaporate. Alternatively, you may spray the solvent suspension onto a grid using an aerosol delivery device. 

Nice Papers (One Thorough Review Article) Related to Nanocluster Growth 

Experimental parameter Resultant porosity Resultant etching rate Resulting critical current 

Anodization time Increase Minimal effect No effect 

Wafer doping (p-type) Decrease Increase Increase 

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T. Fukasawa, Z, Y, Deng, and M. Ando, Synthesis of Porous Silicon Nitride with Unidirectionally Aligned Channels Using Freeze-drying Process, J. Am. Ceram. Soc., 85 [9] 2151-2155 (2002),... 

Adachi S, Tomioka K (2005) Visible light emission from porous silicon prepared by photoetching in alkaline solution. Electrochem Solid-State Lett 8 G251-G253 Andersen OK, Frello T, Veje E (1995) Photoindueed synthesis of porous silicon without anodization. J Appl Phys 78 6189-6192... 

Quantum dots provide a great example of the enabling role that chemistry plays in the synthesis of nanomaterials. In that case, we harness the solubility rules to generate our nanomaterials. A simplified precipitation reaction for the synthesis of CdSe is shown in Figure 14.4. This type of nanoscale synthesis is often referred to as bottom-up because it starts with molecular or atomic building blocks. The other main approach to synthesize nanomaterials is called top-down, in which we carve out a nanostructure from something larger. An example of this is found in the electrochemical synthesis of porous silicon nanostructures from crystalline silicon wafers. 

A. A Malygin, Synthesis of Multicomponent Oxide Low-Dimension Systems on Surface of Porous Silicon Dioxide Using Molecular Layering Method, J. General Chem. (in Russian) 72(4), 617-632 (2002). 

Lin CC, Yen YC, Wu HC, Wu NL (2012) Synthesis of porous Si particles by metal-assisted chemical etching for Li-ion battery application. J Chin Chem Soc 59 1226-1232 Liu Y, Chen B, Cao F, Chan HLW, Zhao X, Yuan J (2012) One-pot synthesis of three-dimensional silver-embedded porous silicon micronparticle for lithium-ion batteries. J Mater Chem 21 17083-17086... 

Kovalev D, Heckler H, Averboukh B, Ben-Chorin M, Schwartzkopff M, Koch F (1998) Hole burning spectroscopy of porous silicon. Phys Rev B 57(7) 3741-3744 McKeever SWS (1984) Thermoluminescence in quartz and silica. Radiat Prot Dosim 8(l/2) 81-98 Moscovitch M, Horowitz YS (2007) Thermoluminescent materials for medical applications LiF Mg, Ti and LiFiMg, Cu, P. Radiat Meas 41 S71-S77 Pincik E, Bartos P, Jergel M, Falcony C, Bartos J, Kucera M, Kakos J (1999) The metastability of porous silicon/crystalline silicon structure. Thin Solid Films 343-344 277-280 Rivera T (2011) Synthesis and thermoluminescent characterization of ceramics materials. In Sikalidis C (ed) Advances in ceramics - synthesis and characterization, processing and specific applications. InTech, Rijeka, Croatia pp 127-164 Skryshevskii YA, Skryshevskii VA (2001) Thermally stimulated luminescence in porous silicon. J Appl Phys 89(5) 2711-2714... 

F. Liebau, Synthesis of porous tectosilicates parameters controlling the pore geometry. Silicone Chemistry (E. R. Correy, J. Y. Correy, and P. P. Gasper, eds.), Ellis Horwood, Chichester, UK, 1988, pp. 309-323. 

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. 

The amorphous silica matrixes are porous network structures that allow other species to penetrate [44]. Thus, the doped dye molecules have the ability to react with targets. However, the reaction kinetics is significantly different than the molecules in a bulk solution. In the synthesis of DDSNs, commonly used silicon alkoxides including TEOS and TMOS have tetrahedron structures, which allow compact polycondensation. As a result, the developed silica nanomatrix can be very dense. The small pore sizes provide limited and narrow pathways for other species to diffuse into the silica matrix. 

Germanium, like silicon, is an important semiconductor with considerable scientific interest because of its many practical technological applications [30-32]. As a result, a large number of synthetic procedures for Ge nanoparticles have been developed that affect size and shape of the final products. Although the synthesis of germanium nanoparticles is well established, the synthesis of Ge semiconductors with porous frameworks is not. 

Our synthesis is based on the hydrolysis of a silicon alkoxide (TEOS Si(OCH2CH3)4) in a diluted solution of nonionic polyethylene oxide-based surfactants. The hydrolysis is then induced by the addition of a small amount of sodium fluoride [5], Depending on the initial mixing conditions, the size of the solubilized objects leads to either a colorless or milky emulsion. Small particles ( 300 nm) with a 3D worm-hole porous structure or small hollow spheres with mesoporous walls, are usually obtained [6]. The synthesis we report herein after exhibits an apparently slight but actually drastic change in the preparation conditions. The main feature of this approach is an intermediate step that utilizes a mild acidity (pH 2 - 4), in which, prior to the reaction, a stable colorless microemulsion containing all reactants is... 

It is well known that the elements in framework of zeolite molecular sieves greatly influence the properties and behaviors of these materials [1-3], The introduction of heteroatoms into the framework has become one of most active fields in study of zeolites. The investigations were mostly focused on the methods to introduce heteroatoms into the framework (for examples, hydrothermal synthesis and post-synthesis), the mechanisms for incorporations, the effect of heteroatoms on the acid-base properties and the catalytic features of modified samples [1-10]. Relatively less attention was paid to the effect of treatment process on the porous properties of samples although the incorporation of heteroatoms, especially by the so-called post-synthesis, frequently changes the distribution of pore size. Recently, we incorporated Al, Ga and B atoms into zeolites (3 by the post-synthesis in an alkaline medium named alumination, galliation and boronation, respectively. It was found that different trivalent elements inserted into the [3 framework at quite different level. The heteroatoms with unsuitable atom size and poor stability in framework were less introduced, leading to that a considerable amount of framework silicon were dissolved under the action of base and the mesopores in zeolite crystal were developed. As a typical case, the boronation of zeolites (3 and the accompanied formation of mesopores are reported in the present paper. 

Trichlorosilane is synthesised in fluidised layer reactors, similar to the apparatuses for the direct synthesis of alkyl- and arylchlorosilanes. For example, it can be a vertical steel cylindrical apparatus with a gas distribution device in the form of a conical bottom. The upper (expanded) part of the tower (expander) separates small particles of silicon carried from the fluidised layer by gas flow. The expander has filters from porous metal inside. (Steel 3). The reactor and expander are electrically heated. Trichlorosilane can also be synthesised in vertical section reactors. 

The hydrogen bond interaction of OH groups at the surface is determined by the Si-O-Si ring size, and its opening degree, the number of hydroxyls per silicon site, and the surface curvature. The concentration of OH groups at the surface is approximately 2-5 x 1018 OH/m2, and it is found to be almost independent of the synthesis conditions of porous silica [162],... 

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