Brief Introduce about how we make an integrated cricuit by silicon.
Why we have to use semiconductor?
Information is stored in our computing system by binary system, zero and one. So how do the computing system store and operate them? It switch between On and Off, representing one and zero. Semiconductors have a number of unique properties, one of them is their variable conductivity. Their conductivity can be changed through doping and gating etc. We can only perform quick switch between high and poor electrical conductivity on semiconductor.
Semiconductor device fabrication & Why silicon?
First, wafers production, a process produce extremely pure silicon as substrate. Then Photolithography, implantation, etching, deposition are used to form transistors on it, connecting them with metals. Silicon is widely used in nowadays in semiconductor. Although there are various kinds of semiconductors,
Silicon has largest reserve, several kinds of chemical/physics methods can be used while other semiconductors do not perform these properties.
But today we are looking at Carbon nanotube (CNT), which is thought to be complement of the next generation integrated circuit.
Introduce to CNTs (Carbon Nanotube)
Carbon nanotubes(CNT) are members of the fullerene structural family; You can understand its structure consider rolls the graphene (one-atom-thick sheets of carbon, sp2 bonds , chickend wire/honeycomb-like ) at a specific pattern. Van der waals force between them (more specifically, the pi-stacking interactions, just like graphite) align them into ropes. The pi bonds in it cause the vast electron delocalization (Aromaticity), the valance electrons are free to move in layers, futher more, in specified direction.
Many of the nanotube prope...
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...r more than one order magnitude. In theory, carbon nanotubes are also able to conduct heat nearly as well as diamond or sapphire, and because of their miniaturized dimensions, the CNTFET should switch reliably using much less power than a silicon-based device. This is important as the microminiaturization of our devices. We are looking forward to more breakthroughs in CNT technology.
The Future
With the continuous development of technology, the fabrication of carbon nanotubes also will be became more and more mature. We are bound to gain cheaper and cheaper carbon nanotubes more efficiently. Doping of Carbon Nanotubes will become more diversified. The application of carbon nanotubes also will be more close to our life, such as body armor made by carbon nanotubes, super computer made by carbon nanotubes. In a word, the prospect of carbon nanotube is immeasurable.
Carbon is one of the 115 chemical elements discovered on Earth which is part of the nonmetals group with other elements such as nitrogen, oxygen, and hydrogen. Carbon as an element has good stability, it is very light, very stable, and has many types of forms such as graphite, and coal. Carbon fiber is just another form of carbon, basically has filaments between five to ten micrometers in diameter of pure carbon or at least 90% of carbon. Thousand carbon fibers are twisted together to form a long chain, which can then be used in a variety of raw forms, including yarns, weaves, and braids, which are in turn mixed with synthetic resins to create the carbon fiber as a composite material. Based on different characteristics carbon fibers can be divided into three principals groups: according to carbon fiber tensile modulus, according to precursor fiber materials, and according to final heat
Due to the varied properties and the scope of application which the CNTs possess, it is of paramount importance that CNTs are produced sufficiently at a competitive cost with the existing technology. The research over two decades, since the discovery of CNTs at Iijima’s Laboratory in 1991, has not helped in reduction of cost or production of CNTs of well-defined properties on a massive scale (Kumar, n.d.). This is mainly because of the complexity in the growth mechanism of CNTs. Extra ordinary properties and applications cannot be unleashed without the fundamental understanding of the growth mechanism of Carbon Nanotubes (Kumar, n.d.). There are several methods to produce Carbon Nanotubes in a laboratory setup. Some of widely used techniques include
Current collectors are made of graphitic materials due to its good conduction. GDL gas diffusion layers are made of carbon paper, which has low electronic resistance in order to provide maximum electronic contact and prevent water flooding. Bipolar plates are made of either graphite sot thermosets materials. [Lister & McLean ]
There is big deal of interest in silicon carbide (SiC) as an electronic material for high-voltage, high-power and high temperature applications. In this thesis, characteristics of Double gate vertical metal semiconductor field effect transistors (MESFET) fabricated on N/N+ 3C-SiC grown on N+ Si substrate are reported. The most intriguing electronic property of silicon carbide is that it is the only semiconductor material other than silicon that can have electronically passivated surface to industrial standards. The surface passivation is the main reason for the dominance of silicon but, in addition to that, silicon carbide has superior bulk properties. This combination of factors raises the question whether silicon carbide can play a role in main stream electronics (integrated-circuit based complex systems). After analysis of both technical and commercial factors and challenges leads to a conclusion that developing a silicon-carbide film on silicon wafers is the most promising way for silicon carbide enter the mainstream electronics. SiC MESFET shows great promise in high power/temperature operations when compared to Si counter parts. The simulations were performed on ATLAS (SILVACO) software, and results are presented.
Carbon Nanotubes could make t-shirts bulletproof. Retrieved March 11, 2014, from Nano Werk: http://nanowerk.com/spotlight/spotids1054.php. Fecht, S. (n.d.). Lighter, stronger bulletproof clothing. Retrieved April 8, 2014, from Popular Mechanics: http://popularmechanics.com/science/health/med-tech/6spidersilksuperpowers.htm.
They can be seen as a collection of rolled sheets of graphene. CNTs demonstrate superconductivity with very large temperature transition. Electrons transport and resistance of CNTs do not depend on the sizes of CNTs. Carbon nanotubes electrodes are constructed by combining graphite powder and multiwall carbon nanotubes in a pestle and a mortar. Then, paraffin is added to the mixture by a syringe before the mixture is packed in a glass tube. After the construction, its electrochemistry is tested to verify its electro-activity by using standard solution of Fe(CN)63-/Fe(CN)64. Care is taken on information about electrode interfaces; mass transiport needs to be minimized in order to be used in catalysis, sensing and electrodeposition (Elrouby, 2013).
In 1824, J.J. Berzelius discovered an amazing element thats in so many things today that many people do not even know they're using it. Silicon. Silicon was discovered by Berzelius
the discovery of carbon nanotubes, the strongest material known to man, a possible solution has been found.
19. Novoselov, Kostya S., et al. "Electric field effect in atomically thin carbon films." science 306.5696 (2004): 666-669.
Silicon surface micromachining uses the same equipment and processes as the electronics semiconductor industry. There are three basic building blocks in this technology, which are the ability to deposit thin films of material on a substrate, to apply a patterned mask on top of the films by photolithographic imaging, and to etch the films selectively to the mask. A MEMS process is usually a structured sequence of these operations to form actual devices.
Fullerenes are accepted as the fourth for of solid carbon after amorphous, graphite and diamond forms. Fullerene chemistry has provided a new dimension of aromatic and a new platform for discussion of mathematical techniques pertinent to large cages. They are basically, large carbon cage molecules. These fullerenes have attracted great interest a large number of physical and chemical properties. These properties of nanostructures strongly depend on this size, shape and chemical compositions. This property leads to very interesting and recent applications in medicinal chemistry, material science and nanotechnology. Functionalization, intercalation and doping by the addition of electron acceptors or donors are the way of modifying the properties of these nanostructures. Among these nanostructures carbon based nanomaterials such as nanotubes, nanocages, nanoshells,
In 2010 two Russian-born scientists pioneered and synthesized a form of “wonder material” that generates heat and electricity at faster speeds, copes with high temperatures, and is almost transparent. Graphene is arranged in a flat hexagon lattice (like microscopic chicken wire) and is one atom thick two-dimensional 〖sp〗^2 bonded carbon. It is the world’s thinnest and strongest material, which can be manufactured into a plethora of provisions that can be used for next generation technology, such as planes, satellites, cars, and computers. However, uses of the material can be expensive and difficult to manufacture for mass production, which is why many of us today do not have access to graphene or use it for various applications in technology in day-to-day life. Graphene is a newly developing material, which is under scrutiny and scientific study in order to integrate it simply and effectively into everyday life.
Grundmann, Marius. Physics of Semiconductors: An Introduction Including Devices and Nanophysics. New York: Springer, 2006. Print.
American Chemical Society. "Carbon nanotubes twice as strong as once thought." ScienceDaily, 16 Sep. 2010. Web. 5 Dec. 2013.
The photovoltaic effect, electricity can be created directly from sunlight. Some semi-conductor materials that are exposed to sunlight can create electron-hole pairs, which can be collected to produce electricity. This occurs when photons have energy above a certain threshold. These photons have shorter wavelengths. In silicon, the threshold for electron-hole production is in the infrared region of the electromagnetic spectrum.