Eur. Phys. J. AP
Volume 8, Number 2, September 1999
|Page(s)||111 - 121|
|Published online||15 September 1999|
Effects of excess carbon and vibrational properties in ultrafine SiC powders
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: email@example.com
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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