OPTICAL PROPERTIES OF CARBON CLUSTERS EMBEDDED IN SiO₂ FILMS

Abstract

Raman spectra were measured for carbon-doped SiO 2 thin films prepared by an rf cosputtering method. The changes in the spectra were systematically studied as a function of the annealing temperature. From a detailed analysis of the spectra, the following conclusions were drawn. In the as-deposited films, very small carbon clusters are embedded in the SiO 2 matrices. When the films are annealed at 600°C, graphite-like sp 2 bonds begin to develop in the clusters. Upon annealing with higher temperatures, the size of sp 2 bond clusters increases. However, the growth of graphite microcrystals can be ruled out, since high-resolution transmission electron microscopic images of the samples annealed at 1000°C do not show lattice fringes due to graphite microcrystals. The samples annealed at 1000°C were found to exhibit an extinction hump around 220 nm, very similar to that seen in the interstellar extinction spectra.

Silicon Compound Nanomaterials: Exploring Emission Mechanisms and Photobiological Applications

“…The role of NPs size in describing the PL mechanisms of the SiO x C y matrix was first explained by Hayashi et al, where the role of carbon clusters in the SiO x C y matrix was discussed, concluding that carbon clusters (≈2 nm), equal to or smaller than C60, could influence PL in the 2.2 eV band. [ 147,148 ] B. Garrido et al also described the role of QDs in SiO 2 implanted with carbon and Si and explained the reason for PL at different bands such as 1.4–1.6, 2–2.2, and 2.7 eV, due to the formation of QDs (1.4–1.6 eV), amorphous carbon clusters (2‐2.2 eV), and SiC clustering (2.7 eV), respectively. [ 149–151 ] Moreover, other authors suggested as well that the formation of NCs, amorphous carbon clusters, SiC, and/or a complex of Si, O, and C such as Si y C 1− y O x complexes ( x < 2) could exert influence for PL at 1.9, 2.1, and 2.7 eV bands, respectively.…”

“…The role of NPs size in describing the PL mechanisms of the SiO x C y matrix was first explained by Hayashi et al, where the role of carbon clusters in the SiO x C y matrix was discussed, concluding that carbon clusters (%2 nm), equal to or smaller than C60, could influence PL in the 2.2 eV band. [147,148] B. Garrido et al also described the role of QDs in SiO 2 implanted with…”