Sunday, August 15, 2010

Hexagonal Boron Nitride

Graphene, a single-atom thick allotrope of carbon and an electrical conductor, is considered to be a possible successor to silicon in microelectronics applications.
Hexagonal boron nitride (h-BN) is an insulator. It is highly elastic and nearly as strong as graphene. Rice University scientists have found a way to implant sheets of h-BN into sheets of graphene, which controls the sheet's electronic character.
They have also found a way to deposit sheets of pure h-BN, 1 to 5 atoms thick, onto a copper substrate using a chemical vapour deposition process at about 1,000oC. The h-BN material can then be transferred to other substrates. The size of h-BN sheets is limited only be the size of the copper foil and furnace used to grow it.
It should be possible to draw microscopic patterns of graphene and h-BN, useful in creating nanoscale field-effect transistors, quantum capacitors or biosensors.

Reference:
Li Song, Lijie Ci, Hao Lu, Pavel B. Sorokin, Chuanhong Jin, Jie Ni, Alexander G. Kvashnin, Dmitry G. Kvashnin, Jun Lou, Boris I. Yakobson and Pulickel M. Ajayan. Large Scale Growth and Characterization of Atomic Hexagonal Boron Nitride Layers. Nano Letters, 2010; 100722142755098 DOI: 10.1021/nl1022139


Study Questions
  1. What is meant by the term allotrope?
  2. What are the naturally occurring allotropes of carbon?
  3. In what ways are these allotropes of carbon the same?
  4. In what ways are these allotropes of carbon different?
  5. If the formula for boron nitride is BN, what is the oxidation state (number) of boron?
  6. Given the name hexagonal boron nitride, draw a possible Lewis Structure (electron dot diagram) for hexagonal boron nitride.
  7. In what ways are graphite and hexagonal boron nitride the same?
  8. In what ways are graphite and hexagonal boron nitride different?
  9. Why is graphite a conductor while hexagonal boron nitride is an insulator?

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