Effect of Amorphous Si Thickness on the Formation of SiC Nanoparticles during High Vacuum Annealing

In this paper, a novel approach for the formation of SiC nanoparticles (np-SiC) has been demonstrated by annealing the three-layer a-Si/C/a-Si film on a Si(100) substrate. The np-SiC formation strongly depends on the amorphous Si (a-Si) thickness and annealing temperature. Both three-layer a-Si/C/a-Si structures in different thickness i.e. 50/200/50 nm and 75/150/75 nm were studied at annealing temperatures of high vacuum annealing at 500-900 degC at 10^-4 Pa. The a-Si thickness and annealing temperature significantly affected the particle size, density, and distribution of np-SiC. No nanoparticles were formed for multilayers annealed at 500 degC, while a few particles started to appear as the annealing temperature was increased to 700 degC at both structures. Many np-SiC appeared at 900 degC at a density order about 10⁸ cm^-2 for both structure, but the thicker a-Si structure i.e. a-Si/C/a-Si (75/150/75 nm) has a particle density approximately 1.8 times higher than a-Si/C/a-Si (50/200/50 nm). This is attributed to the variation of activation energy, surface energy and atomic mobility during reaction of Si and C at different a-Si thickness and temperature. The higher the annealing temperature, the higher the particle density. The thicker a-Si structure with higher density implies that it has lower activation energy of SiC formation than the thin a-Si structure.