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History and Production of Graphene
In the past few years, graphene has been manufactured at a very small scale, but recently a group of researchers have devised a method in which transparent sheets of graphene can be produced that are a few centimeters wide and the thickness ranges from one to six nanometers. It is currently being manufactured is small quantities which are mostly used for experimental purposes.
The most common technique that is being used nowadays is called the "Scotch tape method." In this method, graphene flakes are peeled off from a chunk of graphite using a tape- as graphite itself is a pile of graphene sheets. These graphene sheets are then assembled over a large area for manufacturing of large scale devices.
In another method, thick sheets of graphene are manufactured with the help of graphene oxidized flakes. First, the graphite flakes are oxidized using acids. Oxygen atoms are produced in the graphene sheets which forces them apart. The resultant product is the graphene oxide sheets. These sheets are then suspended in water. It is then filtered through a membrane which has very small pores. The graphene oxide flakes cover the pores. In this way a graphene film is deposited on the membrane. The membrane is then washed with acetone, and the film is exposed to hydrazine. Hydrazine converts the graphene oxide into pure graphene.
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Graphene Semiconductor - Can Graphene replace Silicon?
Graphene is a 2-dimensional material in which the electrons roam around 10 times more freely than they do in silicon atoms. In electronic devices, the flow of electricity can be controlled much more easily by using graphene instead of silicon. It is believed that the limits to the size reduction in silicon chips have been reached, and if we continue to reduce it, then it will get much more expensive and complicated. Silicon chips operate in the gigahertz range, while it is estimated that the graphene chips will be able to operate in the terahertz range- which means that trillions of operations can be carried out in one second.
The research shows that graphene is a much more stable material than silicon as its transistors, having a few atoms, have the ability to sustain very high currents. Graphene has all the properties of a true semi-conductors except one. A graphene chip will continue to draw electricity in a continuous flow and it will not turn OFF. In other words, unlike silicon, it cannot act as a switch. Researchers believe that the ribbons inside the graphene sheets can be cut in such a way that it will be able to turn ON and OFF. It is less likely that graphene will have it's applications in digital applications. It will have its major applications in satellite communications, radars, and image processing. Graphene transistors are being made which are very efficient in amplifying weak signals.
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Nanocircuitry on Graphene
Researchers and scientists have made a breakthrough towards the use of graphene in NanoCircuitry. It is believed that graphene transistors will completely replace silicon transistors at this small scale. A simple one-step process has been introduced for creating nanocircuitry on graphene. This technique is called "Thermochemical Nanolithography" and is used for creating nanowires.
This technique was used to increase the temperature of the graphene oxide, which enables then to design graphene like nanocircuits. In this way the graphene oxide starts to conduct even more. So basically the graphene oxide, which acts as an insulator, can be converted into a conductor by applying a nanoheater. This helps in drawing nanowires with a very high speed, which helps in making nanocircuits more efficient.
Graphene nanocircuits will be faster, and they will consume much less power than silicon nanocircuits. Graphene nanocircuitry is not only used in electronics, but it is expected to work as efficiently in the field of biotechnology where electrical signals from biological cells have to be measured.