Thickness effect on the formation of SiC nanoparticles in sandwiched Si/C/Si and C/Si multilayers

Abstract

The effect of carbon (C) and amorphous silicon (a–Si) thicknesses on the formation of SiC nanoparticles (np–SiC) in sandwiched Si/C/Si and C/Si multilayers on Si(100) substrates were investigated using ultra-high-vacuum ion beam sputtering system and vacuum thermal annealing at 500, 700, 900 °C for 1.0 h. Three-layer a–Si/C/a–Si structures with thicknesses of 50/200/50 nm and 75/150/75 nm and a two-layer C/a–Si structure of 200/50 nm were examined in this study. The size and density of np–SiC were strongly influenced by the annealing temperature, a–Si thickness and layer number. Many np–SiC appeared at 900 °C at a density order about 10 8 cm − 2 in both three-layer structures while no particles formed in the two-layer structure. The thick a–Si structure (75/150/75 nm) produces a particle density approximately 1.8 times higher than thin structure (50/200/50 nm). This implies that thick a–Si structure had a lower activation energy of SiC formation compared to the thin a–Si structure. Few particles were found at 700 °C and no particles at 500 °C in both three-layer structures. The np–SiC formation is a thermally activated reaction. The higher temperature leads to higher particle density. A mechanism of np–SiC formation in thermodynamic and kinetic viewpoints is proposed.