In situ-grown silicon quantum dots in SiCx:H/a-C:H hetero-multilayer films prepared by plasma enhanced chemical vapor deposition method

Silicon quantum dots (Si QDs) were grown in situ in SiCx:H/a-C:H hetero-multilayer films at a low substrate temperature using a radio frequency (13.56 MHz) plasma enhanced chemical vapor deposition (PECVD) method. The component and bonding configuration of the SiCx:H/a-C:H hetero-multilayer films have been systematically investigated by Raman, FTIR and HRTEM testing techniques. The results show that there are amorphous Si QDs in SiCx:H/a-C:H hetero-multilayer films. Without high temperature post-deposition annealing treatments, as increasing CH4 flow rate, the coexistence of amorphous Si QDs and silicon nanocrystals in SiCx:H matrix layers has been confirmed by Raman, HRTEM and FTIR measurements. X-ray photoelectron spectroscopy and UV-Vis spectrometry measurements show that the a-C:H layer is mainly consisted of the sp2-bonded and sp3-bonded carbon atoms and its optical band gap is 1.63 eV. The smaller optical band gap suggested that SiCx:H/a-C:H hetero-multilayer films can reduce the barrier height between Si QDs and barrier layer in vertical direction as compared with SiCx/SiC multilayer films.