Effect of underlying silicon layer on microstructure and photoluminescence of rapid-thermal-annealed carbon and C/Si nanofilms

•Photoluminescence (PL) of carbon films originated from recombination of confined electron–hole pairs.•Broad PL was an interesting topic using varied methods for Si and C reaction.•Asymmetrical broad PL of two-layer Si/C and three-layer Si/C/Si was demonstrated previously.•Here, another C/Si (underlying Si layer) films have further investigated for enhancement of symmetry-like PL.•The effect and mechanism of underlying Si layer thickness on microstructure and PL evolution of two-layer C/Si was studied.

A composite material for broad photoluminescence (PL) from asymmetry to more symmetry-like was proposed by the formation of Si nanocrystals (nc-Si), SiC nanoparticles (np-SiC) and sp2 carbon cluster which were made from the two-layer C/Si on Si(1 0 0) using rapid-thermal-annealing at 750 °C for 1 min. The effect of underlying Si layer thickness on the microstructure and broad PL of the annealed carbon and two-layer C/Si films has been investigated. Fourier-transform-infrared-absorption spectra indicated that very weak Si–C bonding peak was observed for the annealed single-C film and the enhanced intensity occurred at two-layer C/Si films with underlying thickness of 10–25 nm. Compared to the single-C film, the two-layer C/Si film was beneficial for formation of SiC which increased with Si thickness. A more symmetry-like broad PL band around 400–700 nm was observed at the annealed C/Si films with higher Si thickness of 25 nm while the annealed C film has weak and narrow band. Also, the enhanced symmetry-like PL band was attributed to more amount of np-SiC formation at the bottom of C/Si film together with reduced C thickness which can be potentially applied into white light emission material. The detailed mechanism of broad PL was proposed in terms of microstructure evolution.