Chemical Vapor Deposition

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Carbon nanotubes after 940 minutes CVD deposition at 900° C

Chemical Vapor Deposition (CVD) is a versatile materials fabrication process that has been refined to manufacture a number of materials ranging from single and multiwall nanotubes to integrated circuits to entire nanomachines[1].  CVD comes in a number of forms.  Materials like single wall and multiwall carbon nanotubes can be produced by varying the temperature of the CVD process[2].  Types of chemical vapor deposition are differentiated by the materials vaporized, the amount of pressure applied during the process, and the energy source used to induce decomposition and deposition of the vapor.  Regardless of the type of deposition, they all have a number of common benefits over other materials fabrication processes.  CVD produces coatings that can be either used as is or further refined into bulk materials like fibers, wires and powders.  CVD coatings produce materials on the micro or nanoscale, of very high purity, and with better physical characteristics than conventional ceramic fabrication processes[3]

The CVD fabrication process consists of a number of components, mainly a gas delivery system, a reaction chamber, an exhaust system and an energy source that produces thermal, electrical, or photonic energy.  Gas that contains the material to be deposited along with other catalysts enters the reaction chamber, a vacuum that prevents contamination.  In the reaction chamber, an energy source induces the reaction, depositing the precursor vapor onto a substrate in the chamber.  The gas then exits the chamber where it may be processed or further filtered to render it as environmentally and ecologically inert as possible.  The energy source can be a tube furnace, laser, high-energy radio frequencies or another source.


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