The influence of annealing treatments on the microstructural and optical properties of a-SiCx:H films embedded with carbon nanodots

Abstract

In order to obtain the carbon nanodots dispersed in the solid state films, carbon-rich amorphous hydrogenated silicon carbide (a-SiCx:H) films were prepared by PECVD method and were subsequently annealed at Argon protective environment for 30 min with different annealing temperatures (Ta). Raman spectra show that the amorphous carbon nanodots were formed within the a-SiCx:H films as Ta is equal to and higher than 600 °C. Meanwhile, the decomposition and transformation from sp3 C to sp2 C of the carbon nanodots can be inferred by the Raman spectra with increasing Ta. XPS analysis suggest that the near-surface oxidation of the films become strong as Ta > 600 °C which can be contributed to the chemical bond reconstruction and the formation of carbon nanodots within the films. The decrease of the optical band gap derived from the measured absorption spectra of the films can be attributed to the formation and graphitization of the carbon nanodots within the a-SiCx:H films. HRTEM measurements indicate that the enhancement of the areal density and the size reduction of the carbon nanodots take place within the a-SiCx:H films with increasing Ta. However, the dispersion of the carbon nanodots embedded in the a-SiCx:H films is still very bad compared with that of the CQDs dispersed in chemical solvents. PL measurements show that the PL signals may originate from the related defect states rather than the carbon nanodots within the a-SiCx:H films.