Raman inspection for the annealing induced evolution of sp2 and sp3 bonding behavior in sandwiched Si/C/Si multilayer

The effect of annealing on the sandwiched Si/C/Si multilayer on a Si(100) substrate using ion beam sputtering (IBS) system under ultra-high vacuum (UHV) was investigated. Carbon layer thickness was fixed at 100 nm and a-Si ranged from 10 nm to 25 nm. Rapid thermal annealing was performed to investigate the evolution of sp2–sp3 bonding at annealing temperature from room temperature (RT) to 750 °C and annealing time from 0.5 to 2 min. Raman spectroscopy was utilized to characterize bonding behavior of Si/C/Si multilayers for the variation of graphite peak (G-peak), disorder-induced peak (D-peak) of carbon film at specific wavenumbers shift. The higher the integrated intensity ratio (ID/IG), the more the sp2 bonds is. From experimental results, ID/IG ratio increases with annealing temperature from RT to 750 °C due to graphitization effect for the increased sp2 bonds. However, ID/IG ratio reduces a little with annealing time from 0.5 to 2 min. It implies that a little increase of sp3 bonds of carbon, which is primarily from the sp3 Si–C bonds, can be an index of the formation of SiC. Comparing the effect of both annealing temperature and time on the evolution of sp2–sp3 bonds, the annealing temperature dominates more on the sp2–sp3 evolution of a-Si/C/a-Si on the Si(100) under rapid thermal annealing than the annealing time. Also, AES depth profile was used to examine the interdiffusion and reaction between a-Si and C for SiC formation and had a consistent result with Raman.