Abstract
In recent years, the potential applications of Si-based nanostructured materials in the areas of optoelectronic devices have gained much attention especially since the discovery of strong luminescence from semiconductor nanoparticle-containing materials. Ion beam synthesis has been considered as one of the most promising methods to form nanoparticles due to its great processing compatibility with current semiconductor manufacturing technology as well as its excellent controllability in implantation process parameters. The method of sequential implantation of Si+ and С+ ions into SiO2 not only changes the structure of internal matrix but also excites white light emission coupling from multiple luminescent centers. Furthermore, this method creates a glorious prospect for the applications of Si-based optoelectronic materials. However, the mechanisms of photoluminescence (PL) originating from Si+/C+-implanted SiO2 are still unclear and need to be clarified. Thus, this study aims to thoroughly investigate the effects of different parameters of ion implantation and post-annealing on microstructures and PL characteristics in the Si+/C+ implanted SiO2 films. A comparative analysis was also conducted to clarify the difference of optical properties between the Si+ and Si+/C+ implanted SiO2 films. In this study, thermally-grown SiO2 films on Si substrates were used as the matrix materials. The Si+ ions and C+ ions were separately implanted into the SiO2 films at room temperature. The PL characteristics of the Si+/C+ implanted SiO2 films were analyzed using a fluorescence spectrophotometer. The results revealed that the distinct PL peaks were observed at approximately 310, 450 and 650 nm in the Si+ implanted SiO2 films, which can be attributed to the defects, so called oxygen deficiency centers (ODCs) and Non-Bridging Oxygen Hole Center (NBOHC), in the Si+ implanted SiO2 materials. In contrast to the Si+ ion implantation, the SiO2 films which were sequentially implanted with Si+ and C+ ions and annealed at 1100°C can emit white light corresponding to the PL peaks located at around 410, 520 and 720 nm, those can be assigned to the Si-C bonding, C-C graphite-like structure (sp2), and Si nanocrystals, respectively. Moreover, the intensity of PL peaks varied with post-annealing temperature, which implied that thermal annealing treatment could induce (1) defect recovery, (2) bonding of implanted ions with matrix atoms and (3) nanocrystal formation which would influence the PL luminescence properties. Moreover, this study attempted to establish a correlation among optical properties, microstructures, and bonding configurations of the Si+/C+ implanted SiO2 films using some sophisticated experimental equipment.