Issue |
Eur. Phys. J. AP
Volume 8, Number 2, September 1999
|
|
---|---|---|
Page(s) | 111 - 121 | |
DOI | https://doi.org/10.1051/epjap:1999236 | |
Published online | 15 September 1999 |
https://doi.org/10.1051/epjap:1999236
Effects of excess carbon and vibrational properties in ultrafine SiC powders
1
Laboratoire de Physique de l'état condensé (UPRES-A CNRS 6087),
Université du Maine, Faculté des Sciences,
avenue Olivier Messiaen, 72085 Le Mans Cedex 09, France
2
CEMES (UPR CNRS 8011), B.P. 4347, 29 rue Jeanne Marvig,
31055 Toulouse Cedex, France
3
CEA-DRECAM, Service des Photons Atomes et Molécules, CE Saclay,
91191 Gif-sur-Yvette Cedex, France
Corresponding author: kassiba@aviion.univ-lemans.fr
Received:
7
January
1999
Revised:
28
June
1999
Accepted:
31
August
1999
Published online: 15 September 1999
Structural and vibrational properties are investigated in SiC nanopowders synthesized by a CO2 laser pyrolysis of (SiH4, C2H2) gaseous mixture and thermally treated up to 1800 °C. The structural modifications of the SiC crystallites and the arrangement of the carbon in excess are monitored at different annealing stages. A critical behaviour is revealed in the powder annealed at Ta = 1500 °C through the features of the Raman spectra and the insulating-conductor transition. The significant electric conductivity (σ ≈ 0.05 S cm−1) which appears above Ta is discussed with respect to the powder composition and the interface effects where the carbon in excess seems to play a key role.
PACS: 78.30.-j – Infrared and Raman spectra / 78.66.Jg – Amorphous semiconductors; glasses; nanocrystalline materials / 73.61.Tm – Nanocrystalline materials
© EDP Sciences, 1999
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