Chemical vapor deposition precursor delivery

Similar to chemical vapor deposition, reactants or precursors for chemical vapor synthesis are volatile metal-organics, carbonyls, hydrides, chlorides, etc. delivered to the hot-wall reactor as a vapor. A typical laboratory reactor consists of a precursor delivery system, a reaction zone, a particle collector, and a pumping system. Modification of the precursor delivery system and the reaction zone allows synthesis of pure oxide, doped oxide, or multi-component nanoparticles. For example, copper nanoparticles can be prepared from copper acetylacetone complexes [70], while europium doped yttiria can be obtained from their organometallic precursors [71]. 

O Brien P, Pickett NL, et al (2002) Developments in CVD delivery systems, A chemist s perspective on the chemical and physical interactions between precursors. Chemical Vapor Deposition 8(6), 237-249... 

Aerosol-assisted CVD introduces rapid evaporation of the precursor and short delivery time of vapor precursor to the reaction zone. The small diffusion distance between the reactant and intermediates leads to higher deposition rates at relatively low temperatures. Single precursors are more inclined to be used in AACVD therefore, due to good molecular mixing of precursors, the stoichiometry in the synthesis of multicomponent materials can be well controlled. In addition, AACVD can be preformed in an open atmosphere to produce thin or thick oxide films, hence its cost is low compared to sophisticated vacuum systems. CVD methods have also been modified and developed to deposit solid phase from gaseous precursors on highly porous substrates or inside porous media. The two most used deposition methods are known as electrochemical vapor deposition (EVD) and chemical vapor infiltration (CVI). 

Whichever heating method is employed, CVD has to provide a volatile precursor containing the elements that compose the deposited film, transport the precursor towards the substrate surface, enhance or reduce reactions in the gas phase, and provide the surface reaction needed to form the film. The setup consists of a reaction chamber gas/vapor delivery lines the energy source vacuum systems (LPCVD) an exhaust system and gas flow, pressure and temperature monitoring systems. Hazardous vapors are also frequently used and may be produced by chemical reactions. Thus, safety equipment may be necessary. The advantages of CVD films are good... 

---