Raman analysis of the microstructures of nano-silicon coatings grown on different substrates

Abstract

5μm thickness silicon coatings were deposited on RB-SiC、S-SiC、Si and Bk7 substrates using ion-assisted e-beam evaporation method, respectively. Renishaw inVia confocal laser Raman spectrometer was used to study the microstructure of all the samples. The measurement results show that the substrate’s thermal expansion coefficient has great influence on the microstructure of nano-silicon coatings. Owing to 300 degree deposition temperature, there will be thermal stress when the samples are cooled down, which leading to medium-range and short-range order of silicon molecular structure change. Accordingly, TA and TO2 mode will appear or disappear in Raman scattering spectra. Amorphous silicon coating can crystalize after laser irradiation with different Raman scattering TO peak offset for different substrates. Especially for nanosilicon coatings grown on reaction bonded SiC (RB-SiC) and Sintered SiC (S-SiC) under the same deposition conditions, they have different Raman scattering spectra and their thermal stress is different, which will give guidance to deposition and polishing process of nano-silicon layers.