Nanostructured materials chemical vapor deposition

According to Ref. [12], template for synthesis of nanomaterials is defined as a central structure within which a network forms in such a way that removal of this template creates a filled cavity with morphological or stereochemical features related to those of the template. The template synthesis was applied for preparation of various nanostructures inside different three-dimensional nanoporous structures. Chemically, these materials are presented by polymers, metals, oxides, carbides and other substances. Synthetic methods include electrochemical deposition, electroless deposition, chemical polymerization, sol-gel deposition and chemical vapor deposition. These works were reviewed in Refs. [12,20]. An essential feature of this... 

Until recently, synthesis of nanostructured carbon materials was usually based on very harsh conditions such as electric arc discharge techniques [1], chemical vapor deposition [2], or catalytic pyrolysis of organic compounds [3]. In addition (excluding activated carbons), only little research has been done to synthesize and recognize the structure of carbon materials based on natural resources. This is somewhat hard to understand, as carbon structure synthesis has been practiced from the beginning of civilization on the base of biomass, with the petrochemical age only being a late deviation. A refined approach towards advanced carbon synthesis based on renewable resources would be significant, as the final products provide an important perspective for modern material systems and devices. 

Thin semiconductor films (and other nanostructured materials) are widely used in many applications and, especially, in microelectronics. Current technological trends toward ultimate miniaturization of microelectronic devices require films as thin as less than 5 nm, that is, containing only several atomic layers [1]. Experimental deposition methods have been described in detail in recent reviews [2-7]. Common thin-film deposition techniques are subdivided into two main categories physical deposition and chemical deposition. Physical deposition techniques, such as evaporation, molecular beam epitaxy, or sputtering, involve no chemical surface reactions. In chemical deposition techniques, such as chemical vapor deposition (CVD) and its most important version, atomic layer deposition (ALD), chemical precursors are used to obtain chemical substances or their components deposited on the surface. 

Unfortunately, current S3mthesis techniques, such as chemical vapor deposition, arc discharge, laser ablation, or detonation, typically lead to a mixture of various nanostructures, amorphous carbon, and catalyst particles rather than a particular nanostructure with defined properties, thus limiting the number of potential applications [1]. Even if pure materials were available, the size-dependence of most nanomaterial properties requires a high structural selectivity. In order to fully exploit the great potential of carbon nanostmctures, one needs to provide purification procedures that allow for a selective separation of carbon nanostructures, and methods which enable size control and surface functionalization. 

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. ... 

Liu, Y., S.W. Zha, and M.L. Liu, Novel nanostructured electrodes for solid oxide fuel cells fabricated by combustion chemical vapor deposition (CVD). Advanced Materials, 2004, 16(3) p. 256-260... 

There are a number of experimental techniques used to fabricate self-assembled nanostructures from ZnO and other materials. These techniques include the following vapor-liquid-solid, metalorganic chemical vapor deposition, template-assisted, chemical reaction, molecular beam epitaxy, and reactive sputtering. In this section we provide a brief overview of these techniques. 

The following chapters present the general aspects of different synthesis of nanostructured materials, such as Combustion Synthesis (Chap. 2), Spray Pyrolysis (Chap. 3), Electro spinning (Chap. 4), Catalytical Chemical Vapor Deposition applied in the Synthesis of Carbon Nanotubes and Carbon Nanotubes Forests (Chap. 5), Hydrothermal Synthesis (Chap. 6) and High-Energy Milling (Chap. 7). 

The first part of this section focuses on the main characteristics and fabrication techniques used for obtaining templating membranes and depositing metal nanostructures by suitable electroless and elecuochemical procedures. Methods such as sol-gel (10-12) or chemical vapor deposition (10, 13), which have been used primarily for the template deposition of carbon, oxides, or semiconducting-based materials, will not be considered here in detail. The second part of the section focuses on the electrochemical properties of the fabricated nanomaterials with emphasis on the characteristics and applications of nanoelectrode ensembles (NEEs). 

Liu, Y. Zha, S. Liu, M. (2004). Novel Nanostructured Electrodes for Sohd Oxide Fuel Cells Fabricated by Combustion Chemical Vapor Deposition. Advanced Materials, Vol. 16, No. 3, pp. 256-260, ISSN 15214095... 

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