Lecture 38

Lecture 38 - EEE 352: LECTURE 38 Other faces of Carbon *...

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EEE 352: LECTURE 38 Other faces of Carbon * Graphite * Graphene * Carbon nanotubes
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So far, we have dealt with carbon only in the diamond crystal structure, which is important for Si, Ge, most III-V and many II-VI materials. But, a far more common form of carbon is graphite .
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Graphite is another form in which carbon appears. It’s most common usage is pencil lead (which is not really lead, but graphite). It is also a common lubricant and moderator in nuclear reactors. It has a great many uses.
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Graphite crystallizes as a layered compound. The layers are weakly bound to each other, which gives it its lubricant qualities. In-plane, we have sp 2 bonding, which are called σ bonds. These are strong. Interlayer bonds are formed from the p z orbitals, and these are very weak. It has been known since at least 1947, that the layers form 2d transport layers —e.g., the transport is in the plane of the layers.
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In the plane, the atom make a hexagonal arrangement of atoms. The layers are weakly bonded by the fourth bond normal to the plane. The layers may be stacked in a variety of ways, which makes this normal bond weak. Can we peel off just a single layer?
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Graphene is a single layer of graphite, which has been isolated only in the last few years. It has some remarkable properties, which give a new view of condensed matter physics.
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One combines “s,cky tape” (generic Scotch tape) and highly‐oriented pyroli,c graphite (HOPG) in which the planes are parallel to a top surface to produce a “growth” method for graphene sheets.
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Graphene multi layers From Graphite to Graphene
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This note was uploaded on 10/28/2009 for the course EEE 352 taught by Professor Ferry during the Fall '08 term at ASU.

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Lecture 38 - EEE 352: LECTURE 38 Other faces of Carbon *...

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