Mechanism of growth of nanotubes in growth base in nano-microelectronics (Ph.D.)
Researcher and author: Engineer Afshin Rashid
Note: In the production and propagation and upgrading of nano-transistors, the construction of nanotubes is very important for the construction of nanotubes. At CCVD, low temperatures are typically used and nanotubes grow at temperatures below 0111 degrees.
More than one mechanism can be involved depending on the type of gaseous precursors used, the catalyst used and the operating parameters involved in the growth of carbon nanotubes. The dissolution-infiltration-deposition mechanism is the most common one, which is predominant in low temperature methods. In this mechanism, catalytic nanoparticles of metal alloys or intermediate metals such as nickel, iron, and cobalt (spherical or floating on the substrate surface) are considered hydrocarbon vapors (such as CO, CH4, C2H2, C2H4 and C2H6). It contacts hot catalyst particles with decomposed carbon and hydrogen and permeates the carbon into the substrate metal, when the carbon atom in the catalyst reaches a supersaturated amount, the deposition and growth of carbon nanotubes begins.
If the catalyst interaction with the substrate is weak, the metal with the substrate has an acute contact angle (the nanotube at the bottom of the catalyst) ( if the catalyst interaction with the substrate is strong, the metal with the contact angle with the substrate is open, the nanotube grows above the catalyst ) ( growth base) In the first case, it is possible to produce nanotubes with an open end. The physical shape of the carbon deposited on single-walled, multi-walled, amorphous, and graphitic nanoparticles covering the catalyst nanoparticles depends on many factors such as catalytic particle size, deposition rate. When the deposition rate is equal to or less than the carbon diffusion rate, the graphite layer is formed around the catalytic nanoparticles. When the deposition rate is greater than the carbon diffusion rate, carbon nanotubes form. Catalytic Nanoparticle Size It plays an important role in the growth of nanotubes, generally small size catalysts (less than 01 nm) are active for nucleation and growth of carbon nanotubes. If the particle size is about one nanometer, a single-walled nanotube will form. Catalytic nanoparticles with sizes from 01 to 51 nm lead to the growth of multi-walled nanotubes. Catalytic nanoparticles larger than 51 nm are also coated with amorphous graphite sheets .
Graphene is widely used in electronics due to its unique physical properties. Among these properties, the mobility of charged particles inside the graphene, or the mobility represented by the letter μ, is most important. The mobility value for graphene is 100,000 sV / cm2 . Also, its saturation velocity is reported to be about 107 5 5 s / m. Taken together, these properties make graphene a powerful conductor for electronic applications, including applications in transistors.
Conclusions Growth mechanism of nanotubes in growth base (production, replication and upgrading of nano-transistors)
In the production and reproduction of tubular nano-transistors, carbon nanotube production methods are divided into two general categories, based on solid carbon and gas source methods. CCVD methods generally use lower temperatures for the production of carbon nanotubes than solid carbon sources. Understanding the mechanism of carbon nanotube production in order to optimize its characteristics is a very important approach in the production of nano-transistors. Many parameters such as crystalline particle size, substrate type and deposition rate are involved in these mechanisms. Catalyst size is one of the important factors affecting the characterization of carbon nanotubes, and by changing it can produce single-walled and single-walled carbon nanotubes. Some methods such as electric arc and capability mold They contain carbon nanotubes in the absence of catalysts, which results in the production of higher purity products.