Directed vapor deposition

These routes rely on vapor phase preparation of catalysts by deposition of metal precursors onto carbon or by direct formation of the catalyst in the vapor phase. Direct vapor deposition of volatile molecular precursors such as acetylacetonate complexes onto carbon has been demonstrated by Sivakumar and Tricoli for PtRu and PtRuIr. ... 

A recent innovation in processing of CPs has been direct vapor deposition of films. This is illustrated by the work of Plank et al. [291] who deposited P(ANi) films on substrates such as Cu(110) and Au in ultrahigh vacuiun (10 to 10 " Torr). The source was a resistively heated quartz cell filled with emeraldine base powder. Thicknesses were controlled via control of pressure. Thin films, ca. 10 nm thick, doped with HCl were said to exhibit plasma frequencies in the ar-IR, suggesting a high degree of ordering and associated high conductivity, whilst thicker films, ca. 100 nm thick, showed apparently lower conductivity. 

Deposition of Thin Films. Laser photochemical deposition has been extensively studied, especially with respect to fabrication of microelectronic stmctures (see Integrated circuits). This procedure could be used in integrated circuit fabrication for the direct generation of patterns. Laser-aided chemical vapor deposition, which can be used to deposit layers of semiconductors, metals, and insulators, could define the circuit features. The deposits can have dimensions in the micrometer regime and they can be produced in specific patterns. Laser chemical vapor deposition can use either of two approaches. 

Excimer lamps have opened the possibiHty of cost-effective large-area direct photochemical vapor deposition (PCVD). PCVD of stoichiometric, insulating Si02 onto Si wafer has been reported using SiH and N2O as gas-phase precursors and the 172-nm radiation from a Xe 2 lamp (54). Deposition... 

Titanium carbide may also be made by the reaction at high temperature of titanium with carbon titanium tetrachloride with organic compounds such as methane, chloroform, or poly(vinyl chloride) titanium disulfide [12039-13-3] with carbon organotitanates with carbon precursor polymers (31) and titanium tetrachloride with hydrogen and carbon monoxide. Much of this work is directed toward the production of ultrafine (<1 jim) powders. The reaction of titanium tetrachloride with a hydrocarbon-hydrogen mixture at ca 1000°C is used for the chemical vapor deposition (CVD) of thin carbide films used in wear-resistant coatings. 

Chemical vapor deposition competes directly with other coating processes which, in many cases, are more suitable for the application under consideration. These competing processes comprise the physical vapor deposition (PVD) processes of evaporation, sputtering, and ion plating, as well as the molten-material process of thermal spray and the liquid-phase process of solgel. A short description of each process follows. For greater detail, the listed references should be consulted. 

These processes are very rapid and allow the preparation of inorganic supports in one step. This technique allows large-scale manufacturing of supports such as titania, fumed silica, and aluminas. Sometimes the properties of the material differ from the conventional preparation routes and make this approach unique. Multicomponent systems can be also prepared, either by multimetallic solutions or by using a two-nozzle system fed with monometallic solutions [22]. The as-prepared powder can be directly deposited onto substrates, and the process is termed combustion chemical vapor deposition [23]. 

The most important nanomaterial synthesis methods include nanolithography techniques, template-directed syntheses, vapor-phase methods, vapor-liquid-solid (VLS) methods, solution-liquid-solid (SLS) approaches, sol-gel processes, micelle, vapor deposition, solvothermal methods, and pyrolysis methods [1, 2]. For many of these procedures, the control of size and shape, the flexibility in the materials that can be synthesized, and the potential for scaling up, are the main limitations. In general, the understanding of the growth mechanism of any as-... 

In this sub-subsection, the Er doping of amorphous silicon is discussed. The problem of limited solubility of Er in crystalline silicon has been circumvented. However, the electrical properties of pure a-Si are poor compared to c-Si. Therefore, hydrogenated amorphous silicon is much more interesting. Besides, the possibility of depositing a-Si H directly on substrates, i.e., optical materials, would make integration possible. Both low-pressure chemical vapor deposition (LPCVD) [664] and PECVD [665, 666] have been used to make the a-Si H into which Er is implanted. In both methods oxygen is intentionally added to the material, to enhance the luminescence. 

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