石墨烯研究(IJEME-V4-N1-2)

A Study of Graphene

10 A Study of Graphene it. It is one of the thinnest materials in the world as well as one of the strongest in the world, much stronger than steel and lighter. [1]

1.2. Why Graphene?

The answer to this question everyone is asking is its remarkable material properties like ballistic conductance, charge carrier mobilities etc. The properties of graphene are significant in this direction and are discussed in the next section. Standard CMOS technology can be applied to graphene to make much faster devices. Graphene may very well be used as a replacement for indium selenide in solar cells which are relatively more expensive. Pristine graphene boosts of a lot of amicable properties which are very well suited for new electronic devices and applications. However, defects in graphene along with its dielectric environment and high contact resistance might limit the performance. Another significant point to note is that graphene has no energy gap and hence MOSFETs built of graphene will show am bipolar behavior and cannot be switched off. This may very well be one of the reasons as to why the general interest in the industry is now steered more towards analog RF applications instead of the conventional logic RF applications. Graphene optical properties are supposed to be 100 times faster than conventional switches.

The manufacturing process also is a major issue now as the current processes are either not scalable or practical for mass production. Scotch tape technique, where thinner strips are peeled off, of a block of graphite using a sticky tape is not suitable to make the substance in bulk. Graphene is also an atom thick and thereby whatever you do on that might very well hamper the properties which made it desirable in the first place. Another method in place is the chemical vapor decomposition where the carbon atoms are extracted from a carbon rich source by a process called reduction. But this also suffers from the disadvantage of finding a good substrate for growing the graphene on and also for extracting thin layers without any damage.

Much of the above mentioned drawbacks can be limited to a great extent with strides in technological advancements and Graphene as of now holds the key for the industries to engage in this stride. A lot of promising techniques are now emerging but all these are still in a nascent stage and not yet mature. [2]

1.3. Properties of Graphene

Graphene is a single atomic layer of graphite, which is an abundantly found mineral. Graphite is an allotrope of carbon with very tightly bonded carbon atoms organized in the shape of a hexagonal lattice. The sp2 hybridization and thin (0.345Nm) atomic thickness renders very unique properties which are discussed below.

Electronic properties: How electrons flow in a sheet of Graphene, one atom thick is one of the hottest

topics being researched now Graphene is a very good conductor. Research have indicated that electrons can transfer through this sheet at speeds reaching one hundredth the speed of light, as if they carry no mass.

Thermal and thermoelectric properties: The structure of Graphene makes it a perfect thermal conductor.

The thermal conductivity is seen to be much higher than other carbon nanotubes, diamond and graphite. One more property is that the ballistic thermal conductance is isotropic, meaning it is the same in all directions. This property can have important implications for Graphene based electronic devices. High thermal conductivity is vital in dissipating heat efficiently to keep the devices cool.

Mechanical properties: Graphene is harder than Diamond and is seen to be 300 times harder than steel.

Graphene has very high tensile strength and is also very stretchable and robust. This property will have a lot of implications in making a new generation of super strong composite materials. Also special is the fact that coupled with this strong mechanical strength, Graphene also has elastic properties. Tests have shown that Graphene has Spring constant in the order of 1.5 N/m and a Young’s modulus of 0.5 Tpa. The values

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