Construction And Optical Properties Of Silicon Oxycarbide Based Luminescent Materials

In the past decade, luminescent Si-based materials have aroused great research interests owing to their potential application in Si-based monolithic optoelectronic integrated circuits. In recent years, most effort in this field has been directed towards in different Si-based materials such as silicon oxide (SiOx), silicon nitride (SiNx) and silicon carbide (SiCx). In particular, it has reported that efficient photoluminescence as well as optical gain has been achieved in SiOx system. Although research in these systems has made great progress, unfortunately, there is still a long way towards the realization of practical application. The main obstacle lies in the low light emission efficiency. Nowadays, considerable attention has been paid to the light emission from silicon oxycarbide (SiCxOy) films due to its strong white light emission. In our works, in order to search for a highly efficient Si-based luminescent material, we fabricated SiCxOy-based luminescent material and further study the PL mechanism in this system. The detail are as follows:(1) Strong luminescent SiCxOy films were prepared at a low temperature by modulating the oxygen content in very high frequency plasma enhanced chemical vapor deposition system. The prepared SiCxOy films present remarkable photoluminescence with yellow to blue shifting emission when increasing the oxygen content from 29 to 44%. Interestingly, the light emissions in the visible region can be clearly observed with the naked eyes in a bright room. Based on the PL results and the analyses of the bonding configurations of the films, the yellow emission is suggested from the Si-C related defect luminescent centers. Furthermore, the blue PL intensity from the films was found to significantly enhance by a further anneal process. The origin of blue emission was found to be from radiative recombination through Si-related neutral oxygen vacancy defect centers.(2) Strong switchable red Eu3+and blue Eu2+light emissions from Eu-doped amorphous silicon oxycarbide (SiCO) films were fabricated by magnetron sputtering followed by annealing. The evolution of the enhanced light emission strongly depends on the annealing process. Thermal annealing below 800 ℃ results in more than threefold enhancement in red light emission from Eu3+ ions dissolved in SiCO matrix compared with the as-deposited film. By contrast, thermal annealing at>800 ℃ induced a change in the dominant luminescence centers from the 5Doâ†'>7F2 transition of Eu3+ to the 4fs5dâ†'4f7 transition of Eu2+ ions, as well as a 40-fold enhancement in blue-light emission. Combining PLE and X-ray photoelectron spectra with the results of transmission electron microscopy show that the enhanced red/blue light emission is due to the formation of high-density nanosized EuSiO3 clusters that enable energy transfer from nanosized EuSiO3 clusters to Eu3+ and/or Eu2+ ions.