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The Electronic Band -Gap of Polycrystalline Diamond and Tetrahedral Amorphous Carbon by EELS in a STEM.

Published online by Cambridge University Press:  02 July 2020

A.J. Papworth ,
C.J. Kiely  and
G.A.J. Amaratunga
A.J. Papworth
Affiliation:
Materials Research Centre, Lehigh University, Bethlehem, Pennsylvania18015-3195, USA.
C.J. Kiely
Affiliation:
Department of Engineering, Materials Science and Engineering, The University of Liverpool, Liverpool, L69 3BX, U.K.
G.A.J. Amaratunga
Affiliation:
Department of Engineering, The University of Cambridge, Cambridge, UK.
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Extract

Good quality polycrystalline diamond is transparent and has an optical band-gap very close to that of single crystal diamond, 5.5 eV. Tetrahedral amorphous carbon (ta-C) is a form of amorphous carbon which can have up to 90 % sp3 type bonds. It is the form of amorphous carbon, which is closest to having a true diamond-like structure. The optical band-gap of ta-C is however very different from that of polycrystalline diamond, typically in the range 2-3 eV. This difference in the optical bandgap has been ascribed to the electronic states formed by the residual graphitic bonding. The π − π* states at the graphitic sites effectively form tail states on the valance and conduction band edges created by the diamond-like bonding. These tail states extend deep into the band-gap, which would exist if there were only (100 %) diamond-like bonds. The poor electronic properties obtained thus far for ta-C are now accepted as being associated with localised conduction in the π − π* tail states.

Type
Compositional Imaging and Spectroscopy
Information
Microscopy and Microanalysis , Volume 5 , Issue S2: Proceedings: Microscopy & Microanalysis '99, Microscopy Society of America 57th Annual Meeting, Microbeam Analysis Society 33rd Annual Meeting, Portland, Oregon August 1-5, 1999 , August 1999 , pp. 652 - 653
Copyright
Copyright © Microscopy Society of America

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References

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4.) The authors would like to acknowledge the help of Pringle, S. writing the JDOS computer program, and Chalker, P. for providing the CVD diamond. This work was supported by UK Engineering and Physical Sciences Research Council under research grant GRL12783Google Scholar