Structural characterization of annealed Si1−xCx/SiC multilayers targeting formation of Si nanocrystals in a SiC matrix

Abstract

Amorphous Si1−xCx/SiC multilayer films were prepared by alternating deposition of Si-rich Si1−xCx and near-stoichiometric SiC layers by using magnetron sputtering. The as-deposited films were annealed at different temperatures (Ta) from 800 to 1100 °C. The influence of Ta and Si content in the Si-rich layer on the layered structural stability and on the formation of Si and/or SiC nanocrystals (NCs) is investigated by a variety of analytical techniques, including x-ray reflectivity (XRR), x-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, and Fourier transform infrared spectrometry (FTIR). XRR showed that Si1−xCx/SiC multilayers annealed at temperatures of up to 800 °C retain their layered structure. XRD revealed that Si NCs were formed in samples with a high Si content in the Si-rich layer for Ta≥800 °C. At annealing temperatures of 900 °C or greater, the formation of Si NCs was accompanied by the formation of β-SiC NCs. Additionally, the formation of Si and SiC NCs was confirmed by TEM imaging and Raman spectroscopy. The Si-NC size obtained from the TEM micrographs is within the range of 3–5 nm. The β-SiC NCs are smaller (2–3 nm) than Si NCs. Raman analysis identified an ∼9 cm−1 Raman peak shift in the Si-NC peak to a lower energy with respect to that for bulk Si. FTIR Si–C bond absorption spectra exhibited narrowing of the full width at half maximum and a peak shift toward a higher wave number with increasing Ta. This behavior can be explained by an increase in order as well as an increase in the number of Si–C bonds.