A novel approach for the formation of SiC nanoparticles (np-SiC) is reported.
Deposition of Si/C/Si multilayers on Si(100) wafers by ultra-high-vacuum ion beam
sputtering was followed by thermal annealing in vacuum for conversion into SiC
nanoparticles. The annealing temperature significantly affected the size, density, and
distribution of np-SiC. No nanoparticles were formed for multilayers annealed at
500 °C, while a few particles started to appear when the annealing temperature was increased to
700 °C. At an annealing
temperature of 900 °C, many small SiC nanoparticles, of several tens of nanometres, surrounding larger submicron
ones appeared with a particle density approximately 16 times higher than that observed at
700 °C. The higher the annealing temperature was, the larger the nanoparticle
size, and the higher the density. The higher superheating at
900 °C
increased the amount of stable nuclei, and resulted in a higher particle density compared to that at
700 °C. These particles
grew larger at 900 °C
to reduce the total surface energy of smaller particles due to the higher atomic mobility
and growth rate. The increased free energy of stacking defects during particle growth will
limit the size of large particles, leaving many smaller particles surrounding the
large ones. A mechanism for the np-SiC formation is proposed in this paper.